Latest ESO telbib papers

Evolution of the infrared luminosity function and its corresponding dust-obscured star formation rate density out to z ∼ 6

First Author: Koprowski, M. P.
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.01492.S, 2016.1.00434.S, 2015.1.01528.S, 2012.1.00090.S
BibCode: 2026A&A...706A.345K

We present a new determination of the evolving far-infrared (FIR) galaxy luminosity function (LF) and the resulting inferred evolution of dust-obscured star-formation rate density (ρ_SFR) out to redshift z ∼ 6. To establish the evolving comoving number density of FIR-bright objects, we made use of AS2UDS, a high-resolution ALMA follow-up study of the JCMT SCUBA-2 Cosmology Legacy Survey (S2CLS) submilliter imaging in the UKIDSS UDS survey field. In order to estimate the contributions of faint and low-mass sources, we implemented a method in which the faint-end of the IR LF is inferred by stacking (in stellar mass and redshift bins) the optical and near-infrared samples of star-forming galaxies into the appropriate FIR Herschel and submillimeter JCMT maps. Using this information we determined the faint-end slope of the FIR LF in two intermediate redshift bins (where it can be robustly established) and then adopted this result at all other redshifts. The evolution of the characteristic luminosity of the galaxy FIR LF, L_★, is found to increase monotonically with redshift, evolving as L_★ ∝ z^{1.38 ± 0.07}, while the characteristic number density, Φ_★, is well fit by a double power-law function; it is constant at z < 2.24 and declines as z^{−4.95 ± 0.73} at higher redshifts. We then calculated the evolution of the corresponding dust-obscured star-formation rate density and compared it with the results from a number of recent studies in the literature. Our analysis confirms that dust-obscured star formation activity dominates ρ_SFR at cosmic noon but then becomes progressively less important with increasing redshift. While dusty star-forming galaxies are still found out to the highest redshifts explored here, UV-visible star formation dominates at z > 4, and dust-obscured activity contributes less than 25% to the star formation rate density by z ∼ 6.

LRPayne: Stellar parameters and abundances from low-resolution spectra

First Author: Vernekar, Nagaraj
Instruments: HARPS
ProgramIDs: 082.B-0610
BibCode: 2026A&A...706A.217V

Aims. This paper introduces LRPayne, a novel algorithm designed for the efficient determination of stellar parameters and chemical abundances from low-resolution optical spectra, with a primary focus on data from large-scale galactic surveys such as WEAVE. Methods. LRPayne employs a model-driven approach, utilising a fully connected artificial neural network (ANN), trained on a library of 70 000 synthetic stellar spectra generated using iSpec with 1D model atmospheres and the Turbospectrum synthesis code. We trained the network to predict normalized flux given stellar labels (T_eff, log(g), [Fe/H], v_mic, v_max, and v sin i, plus 24 individual elemental abundances). We subsequently derived stellar parameters from observed spectra by finding the best-fit synthetic spectrum from the ANN using a χ² minimisation technique. The method operates on spectra degraded to a resolution of R=5000 covering the 42006900 Å wavelength range. Results. Internal accuracy tests on synthetic spectra show a median interpolation error of less than 0.13% for 90% of the validation sample. The method accurately recovers most of the input labels from synthetic spectra, even at a signal-to-noise ratio (S/N) of 20, with some expected challenges for elements such as Li, K, and N. Validation on the observed spectra of 25 Gaia FGK benchmark stars and 42 metal-poor stars reveals good agreement with the literature values. For the stellar parameters, the mean differences are 22±87 K for T_eff, 0.19±0.23 dex for log(g), and 0.01±0.17 dex for [Fe/H]. Abundances for elements such as Na, Mg, Si, and most Fe-peak elements (Cr, Ni, V, and Sc) are well-recovered. We note challenges for oxygen, manganese in metal-rich giants, aluminium in metal-poor stars and dwarfs, and deriving log g in hot metal-poor dwarfs, partly due to non-local thermodynamic equilibrium effects and line characteristics. Conclusions. LRPayne demonstrates the possibility of extracting precise stellar parameters and chemical abundances from a large number of low-resolution spectra. Its strong performance across different kinds of stars makes it well-suited for current and future large surveys. The abundance results from LRPayne will be very useful for studying stellar nucleosynthesis and the chemical evolution of our Galaxy on a large scale.

Measuring the intergalactic medium correlation length at 5 < z < 6.1: A fast change at the end of reionization

First Author: Spina, Benedetta
Instruments: XSHOOTER
ProgramIDs: 1103.A-0817
BibCode: 2026A&A...706A.273S

Context. The Lyman-α forest of high-redshift quasars is a powerful probe of the late stages of the epoch of reionization (EoR), in particular thanks to the presence of Gunn-Peterson troughs. These troughs exhibit a broad range of lengths, with some extending up to ∼100 cMpc, suggesting large-scale coherent structures in the intergalactic medium (IGM). Aims. We aim to gain more insight into the presence, extent, and magnitude of correlations in the Lyman-α forest at the end of reionization, at 5 < z < 6.1. In particular, we want to quantify the scales over which correlations are significant in order to help inform the required size of cosmological simulations aiming to capture the evolution of the EoR. Methods. We utilized the extended XQR-30 observational dataset over the redshift range 5 < z < 6.1 (∆z = 0.05) to explore large-scale correlations. After accounting for the relevant systematics, the flux correlation matrix proved to be a powerful tool for probing large-scale correlations across redshifts. We performed a Monte Carlo Markov chain analysis to quantify the extent and strength of the correlation, making use of several functional forms. We moreover employed new large-volume (1.5³ Gpc³) light cones of Lyman-α transmission implementing different reionization scenarios to interpret the observed signal, including a fiducial box employing SCRIPT. Results. We detected strong correlations at redshifts z > 5.3, extending at least tens of megaparsecs and strongly increasing with redshift. Our results suggest a redshift-dependent correlation length, from L ≤ 26.53 (68.47) Mpc at 1σ (2σ) limit at redshift z = 5.0 to L = 252.72^+272.61_−41.61 Mpc L = 252 . 72 − 41.61 + 272.61 Mpc at redshift z = 6.1. On the contrary, our simulations all demonstrate characteristic correlation scales < 60 Mpc with a very slow redshift evolution, in strong tension with our observations. Conclusions. The presence and redshift dependence of correlations in the Lyman-α forest on > 200 Mpc scales at z = 6 indicates that cosmological simulations should be larger than this scale to adequately sample the Lyman-α forest. Despite implementing a fluctuating ultraviolet background and numerous neutral islands at z < 6, and matching well the sightline scatter in the Lyman-α forest, our fiducial SCRIPT-based simulation fails to reproduce the large-scale correlations. It may be that those ingredients are necessary, but insufficient, to understand the unfolding of the EoR.

TDCOSMO: XXIII. Measurement of the Hubble constant from the doubly lensed quasar HE 1104−1805

First Author: Paic, Eric
Instruments: FORS2, MUSE
ProgramIDs: 0102.A-0600, 106.215F, 092.A-0515
BibCode: 2026A&A...706A.270P

Time-delay cosmography leverages strongly lensed quasars to measure the Universe's current expansion rate, H₀, independently from other methods. The latest TDCOSMO milestone measurement primarily used quadruply lensed quasars for their mass profile constraints. However, doubly lensed quasars, being more abundant and offering precise time delays, could expand the sample by a factor of 5, significantly advancing towards a 1% precision measurement of H₀. We present the first TDCOSMO analysis of a doubly imaged source, HE 1104−1805, including the measurement of the four necessary ingredients. First, by combining 17 years of data from the SMARTS, Euler, and WFI telescopes, we measured a time delay of 176.3 ^+11.4_−10.3 − 10.3 + 11.4 days. Second, using MUSE data, we extracted stellar velocity dispersion measurements in three radial bins with 5% to 13% precision. Third, employing F160W HST imaging for lens modelling and marginalising over various modelling choices, we measured the Fermat potential difference between the images. Fourth, using wide-field imaging, we measured the convergence added by objects not included in the lens modelling. By combining these four ingredients, we measured the time delay distance and the angular diameter distance to the deflector, favouring a power-law mass model over a baryonic and dark matter composite model. The measurement was performed blindly to prevent experimenter bias and resulted in a Hubble constant of H₀ = ^+5.8_−5.0 H 0 = 64 . 2 − 5.0 + 5.8 × λ_int km s⁻¹Mpc⁻¹, where λ_int is the internal mass sheet degeneracy parameter. This is in agreement with the TDCOSMO-2025 milestone and its precision for λ_int = 1 is comparable to that obtained with the best-observed quadruply lensed quasars (4─6%). This work is a stepping stone towards a precise measurement of H₀ using a large sample of doubly lensed quasars, supplementing the current sample. The next TDCOSMO milestone paper will include this system in its hierarchical analysis, constraining λ_int and H₀ jointly with multiple lenses.

A JWST Paα Calibration of the Radio Luminosity─Star Formation Rate Relation at z ∼ 1.3

First Author: Seymour, Nick
Instruments: VIRCAM
ProgramIDs: 179.A-2006
BibCode: 2026ApJ...998..306S

As radio emission from normal galaxies is a dust-free tracer of star formation, tracing the star formation history of the Universe is a key goal of the Square Kilometre Array and the Next-Generation Very Large Array. In order to investigate how well radio luminosity traces star formation rate (SFR) in the early Universe, we have examined the radio properties of a JWST Paα sample of galaxies at 1.0 ≲ z ≲ 1.8. In the GOODS-S field, we cross-matched a sample of 506 FRESCO Paα emitters with the 1.23 GHz radio continuum data from the MeerKAT MIGHTEE survey, finding 47 detections. After filtering for active galactic nuclei (via X-ray detections, hot mid-infrared dust, and extended radio emission), as well as blended sources, we obtained a sample of star-forming galaxies comprising 11 cataloged radio detections, 18 noncataloged detections (at ≍3σ─5σ), and 298 undetected sources. Stacking the 298 undetected sources, we obtain a 3.3σ detection in the radio. This sample, along with a local sample of Paα emitters, lies along previous radio luminosity/SFR relations from local (<0.2) to high redshift (z ∼ 1). Fitting the FRESCO data at 1.0 ≲ z ≲ 1.8, we find log(L1.4GHz)= (1.31 ± 0.17) × log(SFRPaα)+ (21.36 ± 0.17), which is consistent with other literature relations. We can explain some of the observed scatter in the L_1.4GHz/SFR_Paα correlation by a toy model in which the synchrotron emission is a delayed/averaged tracer of the instantaneous Paα SFR by ∼10/75 Myr.

A Comprehensive Analysis of the Panchromatic Transmission Spectrum of the Hot-Saturn WASP-96 b: Nondetection of Haze, Possible Sodium Limb Asymmetry, Stellar Characterization, and Formation History

First Author: Wang, Le-Chris
Instruments: FORS2
ProgramIDs: 199.C-0467
BibCode: 2026AJ....171..147W

We conduct a reanalysis of the JWST NIRISS/SOSS observation of the hot-Saturn WASP-96 b. Initial analysis of this data revealed an enhanced Rayleigh scattering slope at the blue end of the transmission spectrum, suggesting the presence of hazes at high altitudes. In this work, we report nondetection of this slope, confirming an atmosphere clear of high-altitude aerosols consistent with the pre-JWST results. Also contrary to the initial result, our results indicate the presence of gray cloud deck, although at relatively low altitudes/high pressures. We further combined the NIRISS/SOSS spectrum with the Very Large Telescope, Hubble Space Telescope, and Spitzer to produce a transmission spectrum from 0.35─5 μm. We constrain the mass fraction of multiple chemical species, including: H₂O =−2.62−0.42+0.43 , K =−5.76−1.13+1.05 , and Na =−3.40−0.92+0.90 . C/O ratio and metallicity are tentatively constrained at substellar values ( C/Oplanet=0.57−0.12+0.07 and [Fe/H]planet=0.01−0.52+0.46 compared to C/O_star = 0.92 ± 0.25 and [Fe/H]_star = 0.24 ± 0.05). Inputting these composition constraints to interior structure models, we constrain a core mass of 43−15+8 M_⊕. This, in addition to our inferred super-stellar refractory-to-oxygen ratio ( ∆log10(R/O)=1.48−0.62+0.57 ) and substellar C/O ratio, suggests that the core of WASP-96 b likely formed outside of the water ice line, underwent disk-driven migration, and accreted its atmosphere inside the carbon soot line. We find evidence of atmospheric leading-trailing terminator asymmetries in the broadened sodium absorption feature with a transit time offset of 50 s, while the water features appear symmetric. CH₄, CO, and CO₂ remain unconstrained due to spectral coverage limits. Upcoming JWST NIRSpec/G395H observations (ID 4082, PI: M. Radica) will be crucial for constraining these carbon-bearing species.

Infrared photometry and calcium triplet spectroscopy of the most metal-poor in situ globular cluster VVV-CL001

First Author: Moya, W. Haro
Instruments: FORS2, VIRCAM
ProgramIDs: 091.D-0389, 089.D-0392, 179.B-2002
BibCode: 2026A&A...706A.114M

Context. The characterization of globular clusters (GCs) in the Galactic bulge is a challenging task due to high extinction and severe stellar crowding. VVV-CL001 is a poorly studied GC located in the inner bulge, known for its extremely old age, extreme velocity, and low metallicity. Given its unique properties, a detailed study of this cluster can provide valuable insights into the early chemical and dynamical evolution of the Milky Way (MW). Aims. The aim of this study was to derive the fundamental parameters of VVV-CL001 including metallicity, heliocentric radial velocity (RV), proper motions (PMs), structural properties, orbit, and age, in order to improve our understanding of its origin and role in the early evolution of the MW. Methods. We combined spectroscopic, astrometric, and photometric data to characterize VVV-CL001. Metallicity and RV were determined from medium-resolution spectra obtained with FORS2 at the Very Large Telescope. PMs were derived using Gaia DR3 data. Near-infrared photometry from the FourStar instrument on Magellan was used to refine the cluster's position, construct a radial density profile, and estimate its age, distance, and reddening. Results. Our results confirm that VVV-CL001 is an old 12.1_−1.2^+1.0 Gyr), metal-poor ([Fe/H] = −2.25 ± 0.05 dex) globular cluster located at a heliocentric position of d_⊙ = 7.1_−1.1^+1.3, with a reddening of E(J − K_s) = 1.40_−0.02^+0.01. Its mean PMs are μ_α^* = −3.68 ± 0.09 mas yr⁻¹ and µ_δ = −1.76 ± 0.10 mas yr⁻¹, and it exhibits a RV of −334 ± 4 km s⁻¹. The cluster follows a retrograde-prograde eccentric (e = 0.76_−0.14^+0.10) orbit, confined within the Galactic plane (|Z|_max = 1.0_−0.32^+0.45 kpc) and inside the bar's radius of influence (R < 5 kpc), with a pericenter of r_peri = 0.6_−0.2^+0.3 kpc and an apocenter of r_apo = 4.5_−1.2^+2.5 kpc. Conclusions. These orbital properties, combined with its ancient age and low metallicity, strongly support an in situ origin for VVV-CL001 and likely membership of the disk GC system that was captured by the potential of the bar during its formation. Thus, VVV-CL001 emerges as a fossil remnant of the earliest phases of Galactic assembly and a valuable tracer of the population that contributed to the formation of the inner thick disk and bulge, which are likely part of the main progenitor of the MW. Our study highlights the relevance of detailed chemo-dynamical analyses in unveiling the origin of GCs in the inner Galaxy.

High five from ASTEP: Three validated planets and two eclipsing binaries in a diverse set of long-period candidates

First Author: Rea, Erika
Instruments: HARPS
ProgramIDs: 1102.C-0923, 109.239V, 112.25W1, 115.286G, 112.261U, 108.22A8, 110.23YQ, 114.27CS, 106.21ER, 0104.C-0413
BibCode: 2026A&A...711A..86R

Context. We present the analysis of five long-period TESS Objects of Interest (TOIs), all orbiting Sun-like stars, with orbital periods exceeding one month. Initially identified by the Transiting Exoplanet Survey Satellite (TESS), we extensively monitored these targets with the Antarctic Search for Transiting Exoplanets (ASTEP), supported by other facilities in the TESS Follow-up Observing Program (TFOP) network. Aims. These targets occupy a relatively underexplored region of the period-radius parameter space, offering valuable primordial probes for planetary formation and migration as warm planets better maintain their evolutionary fingerprints. Methods. To characterise these systems, we leveraged high-resolution speckle imaging to search for nearby stellar companions, and refine stellar parameters using both reconnaissance spectroscopy and spectral energy distribution (SED) fitting. We combined TESS photometry with high-precision ground-based observations from ASTEP, and when available, included additional photometry and radial velocity data. We applied statistical validation to assess the planetary nature of each candidate and used allesfitter to jointly model the photometric and spectroscopic datasets. Results. We validate the planetary nature of three TOIs, including the two warm Saturns TOI-4507 b (8.2 R_⊕, 104 d) and TOI-3457 b (10.0 R_⊕, 32.6 d), as well as the warm sub-Neptune TOI-707 b (2.4 R_⊕, 52.8 d). The remaining two candidates are most consistent with eclipsing binaries, namely TOI-2404 and TOI-4404. Conclusions. These results help populate the sparse regime of warm planets, which serve as key tracers of planetary evolution, and demonstrate ASTEP's effectiveness as a ground-based follow-up instrument for long-period systems.

Constraints on Binarity for the Extreme Oe Variable Star AzV 493

First Author: Oey, M. S.
Instruments: FLAMES, GIRAFFE, XSHOOTER
ProgramIDs: 112.25D1, 109.22V0, 112.25R7
BibCode: 2026PASP..138g4202O

The extreme Oe star AzV 493 is known to show unusual photometric and spectroscopic variability that suggest the presence of an unseen companion in a highly eccentric and long-period (7.3 or 14.6 yr) orbit. We obtained a Chandra/ACIS observation near the putative periastron for the 7.3 yr orbit to test for transient X-ray emission that would confirm its binary nature. Our data only place an upper limit to the X-ray luminosity of L_X < 2.5 × 10³³ erg s⁻¹ based on the 0.5─8 keV flux limit. Additionally, we obtained 4 new spectroscopic observations with the M2FS spectrograph at Magellan and 20 archive FLAMES/GIRAFFE and X-Shooter spectra from ESO/VLT to further constrain the possibility of radial velocity (RV) variation. Statistical analysis of the RV measurements yields inconclusive results regarding the existence of variations. We discuss possible mass limits for a potential companion, which may be a black hole, in the event that the variations are real. The violet-to-red Balmer ratio has also recently inverted, which may be a further indication of a companion.

A deep study of the spiral galaxy W2246f

First Author: Johnston, Evelyn J.
Instruments: MUSE
ProgramIDs: 109.2393, 106.21F0
BibCode: 2026A&A...711A.194J

Aims. In this era of large surveys and statistical studies of galaxies, the beauty in the details of individual galaxies is often lost. In this paper we present a deep study of the spiral galaxy W2246f with MUSE, exploring the spatially resolved stellar and ionised gas properties to understand how it formed and evolved over time. The unusually deep observations of this galaxy with MUSE give us a rare opportunity to study this phenomenon with a better spatial resolution than can normally be achieved with the current IFU surveys of galaxies at a similar redshift (z ∼ 0.09). Methods. We analyse the stellar and gas kinematics, as well as the spatially resolved stellar populations and gas properties, including gas metallicity and the dominant ionisation sources. The derived properties include the stellar mass, radial profiles of luminosity- and mass-weighted mean ages and metallicities, and ionised gas characteristics such as E(B − V), Hα extinction, dust-corrected Hα flux, oxygen abundance using the O3N2 calibrator, Hα luminosity, and the Hα-based star formation rate. Results. Analysis of the stellar populations revealed a negative metallicity gradient, and the mass-weighted ages showed uniformly flat ages across the disc while the luminosity-weighted ages show a negative gradient. We find that the gas metallicity and star formation rate density also drop in the central region of the galaxy where the older luminosity-weighted stellar populations are found. Analysis of the WHAN and WHaD diagrams reveal that in fact the central region is retired, while the rest of the disc is star-forming. Conclusions. We conclude that W2246f is a nice example of a central low-ionisation emission-line region (cLIER) galaxy, where the central kpc is dominated by old, metal-poor stars with little star formation. The cLIER emission is primarily powered by hot evolved stars, while the rest of the disc displays ongoing star formation. These findings are consistent with a scenario of inside-out quenching.

The IACOB project: XVI. Surface helium abundances in Galactic O-type stars: Indications for identifying binary interaction products

First Author: Simon-Diaz, S.
Instruments: FEROS
ProgramIDs: 089.D-0975, 087.D-0946, 086.D-0997, 083.D-0589, 081.D-2008, 073.D-0609, 077.B-0348, 079.D-0564
BibCode: 2026A&A...711A.151S

The presence of massive O-type stars with surfaces enriched by CNO-cycle products has been known since the early 1980s. For many years, internal rotational mixing was assumed to be the dominant mechanism responsible for this chemical contamination. However, accumulating evidence suggests that binary interaction may play an equally important, if not dominant, role.

X-shooter spectroscopy of giant stars in the nuclear star cluster

First Author: Origlia, L.
Instruments: XSHOOTER
ProgramIDs: 099.D-0258
BibCode: 2026A&A...711A.176O

Near-IR spectra of a homogeneous sample of 15 red giants in the Galactic nuclear star cluster, within 1.5 pc of SgrA*, have been acquired with X-shooter at the Very Large Telescope. From these spectra, line-of-sight radial velocities and chemical abundances of iron, carbon, oxygen, and other alpha and light elements have been derived. By combining radial velocities from this study and proper motions from the literature, we computed the orbits of these stars, finding that they have been confined within 12 pc from SgrA* for their entire lifetime, thus strongly suggesting an in situ formation and evolution. Iron abundances between half and twice solar; approximately solar-scaled values within ±0.1 dex for α-elements, Ti, and V; some enhancement of [Na/Fe], [K/Fe], and [Al/Fe]; and some depletion of [C/Fe] with respect to the solar ratios have been measured. The inferred chemical abundance distributions are consistent with a formation from a gas enriched by type II and type I supernovae (SNe) over a prolonged timescale, closely matching those of the metal-rich populations of the inner bulge field and other complex stellar systems like Terzan 5 and Liller 1.

The carbon isotope ratio of β Pic b with high-resolution spectroscopy

First Author: González Picos, D.
Instruments: CRIRES
ProgramIDs: 114.27DX
BibCode: 2026A&A...711A..87G

Isotopic ratios trace the formation and evolution of planets and link their atmospheres to the chemistry of their natal protoplanetary discs. We measure ¹²C/¹³C = 58₋₁₅⁺¹⁸ in the atmosphere of the young super-Jupiter β Pic b from 11 nights of CRIRES+ K-band spectroscopy (ℜ ≍ 100 000) at the Very Large Telescope (VLT). We detect both ¹²CO and ¹³CO and constrain ¹²C/¹³C with a Bayesian retrieval jointly fitted with near-infrared photometry. The inferred ¹²C/¹³C is consistent with the present-day interstellar medium (ISM), is below the solar value, and is comparable to measurements in other young super-Jupiters. We also retrieve T_eff = 1629₋₂₈⁺³⁰ K, near-solar to mildly super-solar metallicity ([M/H] = 0.20₋₀₁₂^+0.16), a solar-like carbon-to-oxygen ratio (C/O = 0.52 ± 0.03), and tentative evidence for thick clouds. We analyse each night independently and combine the results of the six epochs with the highest signal-to-noise ratio (S/N), propagating night-to-night scatter into the final uncertainties. This provides an isotopic benchmark for a directly-imaged planet interior to the CO snow line.

The benefit of multiband high-resolution spectroscopic monitoring for studying stellar transients: The NGC 300 OT2008-1 UVES spectrum as a test case

First Author: Mason, Elena
Instruments: FORS1, UVES
ProgramIDs: 281.D-5016
BibCode: 2026A&A...711A.185M

Aims. This work aims to advocate for the benefit of high-resolution spectroscopic monitoring in the study of local group transients. Taking advantage of the experience gained through a vast and systematic study of transients such novae and non-compact stellar mergers that we monitored through panchromatic high-resolution spectroscopy, we show that a similar approach ─ i.e., a change of paradigm in the observing strategy and the analysis ─ in the study of a number of (local group) transients would be advantageous. Methods. As an exemplary analysis, we focus on the optical transient NGC 300 OT2008-1. Searching the ESO archives, we found a low-resolution (FORS) and a high-resolution (UVES) spectrum that were separated by only one day with no changes between them. We reduced and analyzed each spectrum, comparing the different information accessible in the two cases. Results. The independent analyses of the FORS and UVES spectra show that in the low-resolution spectra we can securely identify only a small sample of lines and are unable to correctly characterize the ejecta energetics, which remain at the level of speculation. Instead, in the high-resolution data, we identify a larger sample of emission lines and analyze their profiles. This points to a complex geometry and ejecta dynamics that are simply impossible to infer in low-resolution spectra. Line profile studies are not possible with low-resolution spectra, and may lead to potentially misleading measures. Additionally, because of the limited information available from low-spectral-resolution data, the interpretation is compromised (e.g., full-width-at-half-maximum measurement of unresolved lines), and the formulation of any realistic physical scenario hindered. The analysis is, thus, limited to parameter fitting to oversimplified, biased, standard models. On this occasion only one epoch was available, but monitoring is fundamental to characterize the transient evolution. In particular, since, based on the UVES spectrum, we propose a new very specific scenario, we discuss how it could have been confirmed or dismissed thanks to high-resolution spectroscopic monitoring. Low- and high-resolution spectra serve different but complementary purposes. With low resolution one does bolometric-like studies (spectral energy distribution, or strengthening or weakening of the major transitions), while with high resolution one does dynamics and precise physical characterization. We also show examples from our past works, on different types of transients for which it was possible, by monitoring them with high-resolution spectroscopy, to disentangle the various components, constrain their physical parameters and the energy source involved, and derive the ejecta dynamics.

A MUSE View of the Optical Torus within the Supernova Remnant 1E 0102.2─7219

First Author: Suherli, Janette
Instruments: MUSE
ProgramIDs: 0104.D-0092
BibCode: 2026ApJ..1006...52S

We present new Multi Unit Spectroscopic Explorer (MUSE) Narrow Field Mode with adaptive optics observations of the optical torus surrounding a central compact object candidate within the oxygen-rich supernova remnant 1E 0102.2─7219 located in the Small Magellanic Cloud. These data provide nearly an order-of-magnitude improvement in spatial resolution over previous MUSE Wide Field Mode observations. The improved spatial resolution resolved the previously identified torus into a cavity-like structure with a sharply defined inner edge and diffuse, outer filamentary substructure. The emission shows continuous velocity connectivity, broad intrinsic line widths, and cospatial contributions from neutral and partially ionized species, including O I, Ne I, [O I], [O II], and [O III]. Spatially resolved line-ratio maps indicate that the emission arises from a multiphase, nonequilibrium medium rather than a single homogeneous component. Comparison with photoionization and shock models shows that no single-component model within the explored parameter space can simultaneously reproduce both the strong neutral and high-ionization diagnostics, indicating that multiple physical conditions must coexist. We favor an interpretation in which shocks propagating through density inhomogeneities in the ejecta shape the observed morphology and excitation, while also considering alternative mechanisms linked to the central source, binary evolution, or interaction with an embedded object within the remnant.

Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra-I cluster: VI. A star-forming UDG in Hydra I: A rare UDG or a transition phase

First Author: Rossi, Luca
Instruments: MUSE
ProgramIDs: 108.222P
BibCode: 2026A&A...711A.149R

Context. This paper presents a detailed analysis of a gas-rich star-forming ultra-diffuse galaxy (UDG) as part of the ESO Large Programme Looking into the faintEst WIth MUSE (LEWIS). Among the UDGs in the LEWIS sample, UDG 6 is the only galaxy that hosts a significant amount of ionised gas with evidence of emission lines, suggesting recent star-forming activity. Aims. The main goal of this work is to constrain the formation history of this UDG by comparing its properties with the main formation scenarios proposed for this extreme class of galaxies. Methods. We adopted integral field spectroscopy from MUSE to derive the morphology and the structural properties of the stellar and gas components of UDG 6. We applied spectral fitting and Voronoi tessellation algorithms to the MUSE data-cube to derive the kinematics and properties of the gas and stellar component, explore gas dynamics, and characterise emission lines. Moreover, we derived the properties of the globular cluster (GC) populations by applying a multi-band spectrophotometric analysis. Results. We confirmed that UDG 6 is a member of the Hydra I cluster and that it has a systemic velocity of V_{sys, *} ∼ 3580 km s⁻¹. It is characterised by a regular and elongated shape and contains a significant dust content (A_V = 1.2 ± 0.5 mag), a metal-poor (12 + log₁₀(O/H) = 7.7 ± 0.2 dex) ionised gas fraction (f_gas = 0.24 ± 0.08), and an underlying old-to-intermediate (≳3 Gyr) stellar component. Evidence of local and clumpy star-forming activity has been revealed through the analysis of emission line ratios, and an arc-like tidal feature was discovered from unsharp masking analysis. The number counts of GCs in UDG 6 is N_GC = 0.2 ± 5.4. Conclusions. Similar to the other UDGs in LEWIS, UDG 6 might originate from a "puffed-up dwarf" whose stellar content has been stretched out to larger radii, passively evolving into a more diffuse galaxy. Since UDG 6 is located in a dynamically active region of the cluster characterised by tidal features and stripping phenomena, we suggest that the environmental processes have played a role in shaping its properties. A tidal interaction with a nearby galaxy might have triggered recent star-formation activity without dramatically altering the coherent gas rotation in UDG 6.

NGTS-39 b: a 58 d transiting warm Jupiter in an eccentric orbit

First Author: Apergis, Ioannis
Instruments: HARPS
ProgramIDs: 116.29B6, 112.261U, 116.28XG
BibCode: 2026MNRAS.550g1271A

We report the discovery and characterization of NGTS-39 b (TIC 453147896 b), a warm Jupiter transiting a Sun-like star on a 58.2 d, eccentric (e =

$0.386\pm 0.019$

) orbit. NGTS-39 b was first identified from a Transiting Exoplanet Survey Satellite single transit event, and subsequently confirmed with NGTS photometry and radial velocity measurements from CORALIE and HARPS. The host star is a bright (

$T_{\mathrm{mag}}$

= 11.02) F9 dwarf with effective temperature of T_eff =

$6053_{-30}^{+67}$

K. NGTS-39 b is a Jupiter-sized gas giant with a radius of

$1.088\pm 0.012$

R_J and a mass of

$1.467\pm 0.081$

M_J. Its equilibrium temperature is

$519_{-5}^{+6}$

K, placing it between short-period hot Jupiters and cold, Jupiter-like giants. The high orbital eccentricity and intermediate equilibrium temperature of NGTS-39 b make it a valuable test case for formation and migration models, particularly in the poorly sampled regime of long-period gas giants. The RV data show a linear trend of

$\dot{\gamma } = -17.75$

m s

$^{-1}$

, which indicates the presence of an outer companion. The discovery of NGTS-39 b contributes to the small but growing population of transiting warm Jupiters with P> 50 d orbiting bright stars.

The small transiting planet population revealed by ESPRESSO with extreme precision radial velocities

First Author: Hobson, M. J.
Instruments: ESPRESSO
ProgramIDs: 112.25BG, 108.2254, 110.24CD, 106.21M2, 1102.C-0958, 1104.C-0350, 0102.C-0456, 1102.C-0744
BibCode: 2026A&A...711A.198H

Context. Small planets are extremely common in the Galaxy, including planets with masses and radii between those of Earth and Neptune. Characterising the mass of such planets requires ultra-precise radial velocities. The ESPRESSO spectrograph was designed and built for this purpose. Aims. We present an overview of the ESPRESSO Guaranteed Time Observations transit follow-up sub-programme, which aimed to confirm and characterise small transiting planet candidates from the K2 and TESS space missions. Methods. We analysed the global stellar and planetary properties of the sample of 65 planets in 30 systems characterised by this subprogramme. This includes six systems presented in this paper, for which we either obtain only the upper mass limits or provide updates to previously published parameters. We also placed this sample in the context of the overall population of precisely characterised small planets. Results. After separating the population into insolation regimes, we find a tentative mass threshold at ≃6 M_⊕ for the rocky to volatile-rich composition transition in the medium-insolation regime, along with a population of likely stripped massive rocky planets in the high-insolation regime. Likewise, we find a correlation between planet mass and stellar metallicity, with more massive planets hosted by more metal-rich stars. We also explored the radius valley, finding that planets below the gap have a tighter mass distribution. We compared planetary masses with typical protoplanetary disk masses, drawing tentative conclusions about likely formation conditions. We also discuss the impact of our observing strategy on our results. Conclusions. The ESPRESSO transit follow-up sub-programme has been highly productive in characterising a diverse population of small planets, which has enabled us to identify population-level features. Likewise, the lessons learned from this sub-programme will be valuable for PLATO follow-up planning.

The breaking of cold traps and onset of titanium in ultra-hot Jupiter atmospheres: WASP-189b in context

First Author: Pelletier, S.
Instruments: HARPS, NIRPS
ProgramIDs: 111.2506
BibCode: 2026A&A...711A.119P

Context. Condensates are ubiquitous to all Solar System planets with significant (>10 mbar) atmospheres. The same is true for most exoplanets with characterised atmospheres, with even ultra-hot exoplanets being able to form clouds on their cooler nightsides. One high-interest condensate is titanium, a highly refractory element that as an oxide (TiO) is a potent optical absorber long believed to be a driver of thermal inversions in highly irradiated exoplanet atmospheres. Observations have shown that some ultra-hot Jupiters have strong thermal inversions despite being significantly Ti-depleted, likely due to cold trapping, raising doubts about whether TiO is the main cause of their inverted temperature structures. Aims. Our aim was to retrieve the titanium-to-iron ratio of the dayside atmosphere of the ultra-hot Jupiter WASP-189b to determine whether the full titanium budget is accounted for in the gas phase. Methods. We analysed thermal emission observations of WASP-189b taken with the HARPS and NIRPS spectrographs using different atmospheric retrieval prescriptions to infer the planet's atmospheric thermal structure and composition. Results. We observed Fe and Ti signals in cross-correlation and measured a sub-solar Ti/Fe ratio for WASP-189b using both free and chemical equilibrium retrieval approaches. We find the Ti/Fe of the planetary atmosphere to be between 28% and 81% (1-σ bounds) that of the stellar value. Conclusions. The slight underabundance of Ti with respect to Fe on the dayside atmosphere of WASP-189b suggests that some titanium is missing from the gas phase, potentially due to a partial nightside cold trap. In the context of the ultra-hot Jupiter population, the onset of titanium in exoplanetary atmospheres appears to occur progressively, coinciding not with when thermal inversions begin but rather when the vapourisation threshold of titanium is reached on the nightside.

The SPHERE infrared survey for exoplanets (SHINE): V. Full sample characterization

First Author: Squicciarini, V.
Instruments: SPHERE
ProgramIDs: 113.2689, 111.24QL, 1104.C-0416, 110.240D
BibCode: 2026A&A...711A.136S

Context. Unbiased surveys of large stellar samples are the prime means through which the prevalence of exoplanets can be derived, and crucial constraints to planet formation models can be set. Direct imaging (DI) is ideally positioned to probe the outer regions (5─300 au) of planetary systems, providing complementary information to techniques such as transits and radial velocities. Aims. We present the full sample of the SpHere INfrared survey for Exoplanets (SHINE), the second largest DI campaign to date. SHINE observed 460 stars between 2015 and 2023 thanks to the guaranteed time observations (GTO) allocated by ESO to the SPHERE consortium at VLT. The goal of this paper is to homogeneously derive the stellar properties of the targets and to define a subsample of young single hosts to be used as a starting point for the final statistical analysis of the survey. Methods. Stellar ages were determined based on kinematic indicators (such as the membership to young moving groups), age diagnostics (lithium abundance, rotation, and activity), and isochrone fitting. A thorough vetting for binarity was undertaken combining astrometric, spectroscopic, and imaging data. Results. A subsample of 333 stars, covering a large extent of stellar ages and masses, was constructed. Selection criteria, global features, as well as the properties of individual stars are reported and discussed.

Disruption of a giant: spectroscopic identification of members in the periphery and tidal tails of ω Centauri

First Author: Kuzma, P. B.
Instruments: FLAMES, GIRAFFE
ProgramIDs: 108.22MM
BibCode: 2026MNRAS.550g1147K

$\omega$

Centauri (

$\omega$

Cen, NGC 5139) is one of the most enigmatic globular clusters in the Milky Way, with the recent detection of tidal tails adding further to its complexity. We report the results of a spectroscopic study of stars in the outer regions of

$\omega$

Cen, which provides an improved characterization of the cluster periphery and confirms the existence of tidal tails. Our targets, which lie in six VLT/FLAMES fields sampling six degrees across the sky, are selected using a Bayesian inference technique. We confirm 157 members of

$\omega$

Cen based on line-of-sight velocity and [Fe/H] measurements, indicating an overall success rate of 93 per cent. We trace stars along the tidal tails to a cluster-centric radius of 3.2 deg, identifying five members in the debris and additional lower-probability candidates. The analysis of the kinematics and metallicities of the new members provides evidence of continuity in these properties from the bound component of the progenitor cluster into its tidal debris. We find that the metallicities of stars in the peripheral regions and tidal tails of

$\omega$

Cen are broadly consistent with those in the Fimbulthul stream to which the cluster has been previously linked. Our study provides a glimpse of the promise of new and forthcoming wide-field multi-object spectrographs for advancing understanding of tidal structures around Milky Way globular clusters.

Spectroscopic analysis of RGB stars in nine open clusters

First Author: Cantanhêde, Saulo de Oliveira
Instruments: CRIRES
ProgramIDs: 089.D-0716
BibCode: 2026MNRAS.550g1103C

Stellar clusters are crucial tools for studying the age, spatial distribution, dynamics, kinematics, and chemical composition of different Galactic stellar populations. In this work, we used red giant stars from open clusters to better understand the extra-mixing process through the carbon, nitrogen, and oxygen (CNO) abundances and

$^{12}$

$^{13}$

$^{16}$

$^{17}$

O and

$^{16}$

$^{18}$

O isotopic ratios determined using high-quality spectra in the visible and near-infrared regions. We analysed the radial velocities and chemical composition of 22 K-type giant stars from nine open clusters (NGC 188, NGC 2682, NGC 3680, NGC 5822, IC 4756, NGC 6633, NGC 3532, NGC 6281, and NGC 5460). High-resolution and high signal-to-noise spectra of stars in the NGC188 cluster were obtained with the ESPaDOnS spectrograph at the Canada─France─Hawaii Telescope in the visible region. The stars in the other clusters were observed with the CRIRES spectrograph at the VLT. We used IRAF to compute radial velocities and TURBOSPECTRUM and MOOG for the chemical analysis. The values obtained for the radial velocities and abundances of the sample are similar to those found in the literature. The results in the visible and infrared support the occurrence and predicted mass dependence of thermohaline mixing on the red giant branch and of rotation-induced mixing on the main sequence. Variations of the initial abundances of

$^{17}$

O and

$^{18}$

O may be needed to explain the dispersion of the oxygen isotopic ratios in red giant stars.

Evolution of dust attenuation in star-forming galaxies with UV slope, stellar mass, and redshift out to z∼5

First Author: Wijesekera, J. V.
Instruments: VIRCAM
ProgramIDs: 179.A-2005, 179.A-2006
BibCode: 2026A&A...711A.189W

Context.To set reliable constraints on the dust-obscured portion of star formation across cosmic time, an accurate calibration of the so-called infrared excess (IRX ≡ L_IR/L_UV) and its dependence on intrinsic galaxy properties is required. While the local IRX-β relation (where F_λ ∝ λ^β) has been widely used to correct for the effects of dust absorption and scattering, many recent high-redshift works show significant inconsistencies. They are most likely caused by differences in the assumed attenuation curves, dust temperatures, and galactic star-to-dust relative morphologies. Aims. We found a dependence of the IRX on the UV slope β, stellar mass M_*, and redshift out to z ≃ 5. We also established consistent functional relations that can be used for correcting the UV/optical-selected galaxy samples for the effects of dust absorption. Methods. This work is based on a K-band selected sample of ∼10⁵ star-forming galaxies detected in the UDS and COSMOS fields. Quiescent sources and known starbursts have been removed, while the IR luminosities were established via stacking in FIR Herschel and JCMT maps. The UV slopes were determined from the spectral energy distribution (SED) fits and stacked IRX values were derived by taking the median of individual IRX measurements in bins of β, M_*, and redshift. Results. While our best-fit IRX-β relation is consistent with a Calzetti-like attenuation curve at β ≳ −1, at bluer values, the IRX appears to increase with redshift due to different mass-completeness limits imposed. When deriving the IRX-β relation in stellar-mass bins, a systematic trend was found, where the effective slope of the attenuation law becomes progressively shallower with increasing mass. We incorporated this into the IRX-β relation through the slope of the underlying reddening law, dA₁₆₀₀/dβ, which is a quadratic function of log(M_*/M_⊙). Expressing IRX as a function of the stellar mass, we find a tight correlation, with IRX rising monotonically with mass, while exhibiting a clear high-mass turnover at z ≲ 2 − 3, consistent with suppressed cold-gas accretion and dust growth in massive systems.

Global and Local Infall in the ASHES Sample (GLASHES). II. Asymmetric Line Profiles Around Dense Cores in 70 μm Dark Massive Clumps

First Author: Morii, Kaho
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00299.S, 2023.1.01150.S, 2024.1.01505.S
BibCode: 2026ApJ..1004..207M

Gravitational collapse is fundamental to star formation, yet direct kinematic evidence of infall at the core scale in high-mass star-forming regions remains poorly constrained. We present the first large-scale statistical study of infall signatures in 304 dense cores within 24 massive 70 μm dark clumps from the Global and Local Infall in the ASHES Sample survey. Using Atacama Large Millimeter/submillimeter Array Band 6 observations of the optically thick tracers HCO⁺ and HNC (J = 3─2), we systematically characterize blue asymmetry line profiles indicative of infalling motions. We employ two complementary metrics, the velocity difference parameter (δ_v) and the asymmetry parameter (A), to quantify infall signatures, finding consistent results across both tracers. Blue asymmetry profiles are detected in ∼50%─60% of cores (δ_v < 0 or A > 0). Spectral classification reveals that ∼60% of cores exhibit double-peaked profiles, and 34% and 39% show blue asymmetry profiles in HCO⁺ and HNC, respectively, with the percentage increasing with core mass and surface density. Accounting for geometric effects that can obscure infall signatures, our results suggest that gravitational collapse is prevalent in and around the cores. Importantly, infall signatures are detected from the prestellar stage and become more dominant as the core's evolution proceeds. Even cores with virial parameters α_vir > 2 show infall signatures, suggesting that external compression may trigger collapse in addition to self-gravity or that line width may include inward motion in addition to turbulence. Furthermore, a moderate correlation between clump-scale and core-scale asymmetry supports a hierarchical collapse scenario, implying a dynamic and multiscale process of high-mass star formation.

Morphological Complexity of NGC 628—A Multiwavelength Multiscale Analysis Using the Ordinal Pattern Framework

First Author: Chanu, Athokpam Langlen
Instruments: ALMA_Band_6
ProgramIDs: 2012.1.00650.S
BibCode: 2026ApJ..1003...50C

As statistical systems, galaxies exhibit a rich interplay between organized structure and stochastic fluctuations across a broad range of spatial scales. This duality motivates the need for quantitative frameworks capable of capturing their morphological complexity. The ordinal patterns framework, along with its associated statistical measures: permutation entropy (H), disequilibrium (D_E), statistical complexity (C), and ordinal network node entropy, has recently emerged as a powerful tool for analyzing such complexity in physical systems. We apply this framework in a multiwavelength, multiscale analysis of the galaxy NGC 628, utilizing observations in the near-ultraviolet, near-infrared, mid-infrared, and millimeter bands. Our results reveal a characteristic spatial scale of approximately 200 pc, marking the transition from small-scale structures influenced by star formation and stellar feedback to larger-scale morphology governed by the galaxy's dynamics. Furthermore, we find that the C versus H trajectories for all wavelengths converge toward a common attractor curve, consistent with the behavior of isotropic Gaussian random fields. This convergence suggests a universal statistical behavior in galactic structure at large scales, despite the differing physical processes traced by each wavelength.

GOALS-JWST: resolved multiphase molecular gas in IRAS 20551-4250 using JWST and ALMA

First Author: Kakkad, D.
Instruments: ALMA_Band_6, MUSE
ProgramIDs: 2022.1.01262.S, 095.B-0049
BibCode: 2026MNRAS.549ag781K

Studying the content and distribution of molecular gas (H

$_{2}$

) provides key insights into how feedback from active galactic nuclei (AGNs) and star formation influences galaxy evolution, since molecular gas is the primary fuel for star formation. Ultra-luminous infrared galaxies (ULIRGs) are ideal candidates to study how AGNs and/or starbursts affect the interstellar medium due to their intense AGN and star-forming activity. We present spatially resolved multiphase molecular gas study of IRAS20551-4250, a nearby (

$z=0.0429$

) ULIRG, using James Webb Space Telescope (JWST)/MIRI-MRS and ALMA. Mid-infrared diagnostics do not rule out the presence of AGNs in IRAS20551-4250. [O III]

$\lambda$

5007 in VLT/MUSE data reveal ionized gas outflows with

$w_{80}^{\rm [OIII]} \sim 790$

km s

$^{-1}$

and

$\dot{M}_{\rm out}^{\rm [OIII]}\lt 0.01$

$_{\odot }$

$^{-1}$

. No outflows are observed in either molecular phases. JWST/MIRI-MRS data reveal several rotational transitions of warm H

$_{2}$

$\sim 500\!-\!1400$

K) within the central

$\sim 4\times 4$

kpc

$^{2}$

region. Excitation temperature maps suggest that the warm H

$_{2}$

is primarily heated by UV radiation from the central source. The CO-based cold molecular component dominates the molecular gas mass, accounting for >95 per cent of the total molecular gas mass. Warm H

$_{2}$

maps show two tidal tails and the velocity centroid maps show disturbed non-rotational motions and a systematic gradient across the field of view, similar to that of ALMA CO-based cold molecular gas and consistent with a late-stage merger. Together, our analysis indicate that the molecular gas composition in IRAS20551-4250 is consistent with ongoing star formation in the host galaxy and the outflows observed in ionized gas phase appear insufficient to expel the molecular gas or quench ongoing star formation.

ALMA Observations of [O I] 145 μm and [N II] 205 μm Emission Lines from Star-forming Galaxies at z ∼ 7

First Author: Fudamoto, Yoshinobu
Instruments: ALMA_Band_5, ALMA_Band_6
ProgramIDs: 2021.1.00247.S, 2022.1.00446.S, 2022.1.00999.S, 2022.1.01384.S
BibCode: 2026ApJ..1004..194F

We present results of new observations of [O I] 145 μm and [N II] 205 μm emission lines from four star-forming galaxies at redshifts between z = 6.58 and 7.68 that have previous detections of [C II] 158 μm and dust continua. Using the Atacama Large Millimeter/submillimeter Array, we successfully detect [O I] 145 μm emission from all targets at >4σ significance. However, [N II] 205 μm emission is undetected in all galaxies (signal-to-noise ratio < 3.5σ) except for a tentative detection from A1689-zD1. From the observed high [C II]/[N II] emission line ratios (≳20−80), we find that most of the [C II] 158 μm emission arises from neutral gas regions (3σ lower limits of ≳74%−96%). From [O I] 145 μm, [C II] 158 μm lines, and IR luminosities, we estimate the neutral gas densities of n_H = 10^3.5─10⁶ cm⁻³ and the far-UV (FUV) radiation strengths of G₀ ∼ 10^2.5─10³. While the neutral gas densities are similar to those of high-redshift starburst galaxies, the FUV strengths are lower compared to both local and high-redshift starbursts. Finally, we estimate atomic hydrogen masses using [O I] 145 μm emission lines and the oxygen abundances measured from recent JWST observations. We find gas mass ratios of f_gas ∼ 0.3─0.8, which are similar to earlier studies using [C II] 158 μm. Starting from this pilot observation, future large [O I] 145 μm emission line surveys will provide us with currently little-known neutral gas properties of star-forming galaxies in the early Universe.

The relationship between accretion and ionized ejection among young stellar objects in the Coronet cluster

First Author: Ghosh, Arpan
Instruments: KMOS
ProgramIDs: 093.C-0657
BibCode: 2026MNRAS.546ag154G

We present results from a coordinated, multi-epoch near-infrared and centimetre radio survey of young stellar objects (YSOs) in the Coronet, aimed at probing the connection between mass accretion and ionised mass-loss. Using VLT-KMOS, we detect Br

$\gamma$

emission in 5 of the 26 targets, which also exhibit 3.3-cm continuum emission in VLA images, consistent with partially ionised jets. For seven additional sources, stringent flux upper limits were obtained. The derived accretion and ionized mass-loss rates for class I and class II YSOs follow a sublinear correlation

$\dot{M}_{\mathrm{ion}} \propto \dot{M}_{\mathrm{acc}}^{0.3}$

, consistent with previous results for class II YSOs but extended here to earlier stages. Multi-epoch observations reveal modest variability in both tracers but no clear temporal correlation between accretion and ejection within time-scales of a few months. The ratio

$\dot{M}_{\mathrm{ion}}/\dot{M}_{\mathrm{acc}}$

shows an anticorrelation with

$\dot{M}_{\mathrm{acc}}$

, increasing with time from class I YSOs to class II YSOs, suggesting an increase in jet-launching efficiency or ionization fraction with evolution. These findings support a direct connection between accretion and outflow across the

$\sim$

Myr time-scale of YSO evolution, while highlighting the complexity of their short-term interplay.

Chemodynamics of Boötes I with S⁵: Revised Velocity Gradient, Dark Matter Density, and Galactic Chemical Evolution Constraints

First Author: Sandford, Nathan R.
Instruments: FLAMES, GIRAFFE
ProgramIDs: 182.B-0372, 185.B-0946
BibCode: 2026ApJ...998...47S

We combine new spectroscopic observations of the ultrafaint dwarf (UFD) galaxy Boötes I (Boo I) from the Southern Stellar Stream Spectroscopic Survey (S⁵) with ∼15 yr of archival spectroscopic data to create the largest sample of stellar kinematics and metallicities to date for any Milky Way UFD. Our combined sample includes 148 members extending out to ∼7 half-light radii (r_h), including 24 newly confirmed members, 18 binary candidates, 15 RR Lyrae stars, and 92 [Fe/H] measurements. Using this larger and more spatially extended sample, we provide updated constraints on Boo I's systemic properties, including its radial population gradients. Properly accounting for perspective rotation effects in a UFD for the first time, we detect a 4σ line-of-sight velocity gradient of 1.2 ± 0.3 km s⁻¹ rh−1 aligned along Boo I's orbit and discuss its potential tidal origins. We also infer a metallicity gradient of −0.10 ± 0.02 dex rh−1 in agreement with previous studies. Using an axisymmetric Jeans model, we provide updated constraints on Boo I's dark matter density profile, which weakly favors a cusped ( γ=1.0−0.6+0.5 ) dark matter profile. Lastly, we reanalyze Boo I's metallicity distribution function with a one-zone galactic chemical evolution model and place new constraints on its rapid, inefficient star formation and strong galactic outflows.

The Discovery of an Active Wind from the Milky Way's Central Black Hole

First Author: Gorski, Mark D.
Instruments: ALMA_Band_6
ProgramIDs: 2016.1.00870.S, 2017.1.00995.S, 2019.1.01559.S
BibCode: 2026ApJ..1004L...7G

Every large galaxy has a black hole in its center. The interaction between the black hole and its host profoundly shapes galactic evolution and the Universe as a whole. The key features of this interaction are black hole jets—or more generally, winds—which every black hole must have. Despite the proximity and importance of our Galaxy's central black hole, Sagittarius A* (Sgr A*), the active wind from it has eluded scientists for over half a century. Here we report the discovery of a large active wind from Sgr A* using unprecedentedly deep (T_b ∼ 30 mK) and high angular resolution (≲0 .″ 25) observations with the Atacama Large Millimeter/Submillimeter Array (ALMA). We detect a large conical clearing in the cold molecular gas surrounding Sgr A* that is at least 1 parsec long and has a ∼45° opening angle. The morphology and energetics of this structure are consistent with active clearing of gas by a hot wind from Sgr A*.

Modeling the Milky Way Circumnuclear Disk: Rosettes and Rings

First Author: Ukani, Asad
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.00040.S
BibCode: 2026ApJ..1004..171U

The Milky Way Galactic Center hosts a ∼4 × 10⁶ M_⊙ supermassive black hole (SMBH), Sagittarius A* (Sgr A*). The dominant structures in its immediate vicinity are the nuclear star cluster (NSC), whose enclosed mass at 2 pc is approximately half that of the SMBH, and the circumnuclear disk (CND)/ring, which extends between ∼0.5 pc and ∼3 pc from Sgr A* and is the largest reservoir of molecular gas in this region. Existing models of the CND commonly use one circular orbit to describe the motion of its gas. Here, we explore a much broader range of models. In the combined potential of Sgr A* and the NSC, we consider non-Keplerian rosette orbits as well as a circular disk, which is formed using a finely spaced set of concentric rings. For both systems, we test various inner/outer radii, inclinations, and position angles, sampling a total of ∼3.3 × 10⁵ models. We then conduct mock observations of all models to construct velocity maps, which we compare with HCN (J = 1─0) observations of the CND. We find that the best-fitting model is a circular disk with inner and outer radii of 1.0 pc and 2.9 pc, an inclination of i = 60°, and a position angle of PA = 35°.

Multiscale Gas Structure and Dynamics in an Extragalactic Central Molecular Zone

First Author: Wang, Liam M.
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.00059.S, 2022.1.00159.S
BibCode: 2026ApJ..1003..231W

The structures and dynamics of the interstellar medium are governed by a combination of self-gravity, external gravity, and various sources of ordered and random motions on different spatial scales. This paper uses Atacama Large Millimeter/submillimeter Array CO (3─2) observations at 0.″1≍5 pc resolution to examine the scale dependence of molecular gas structure and dynamics in the central molecular zone (CMZ) of a nearby galaxy, NGC 3351. We use the dendrogram technique to characterize hierarchical molecular gas structures spanning two decades in spatial scales and measure their size, gas mass, and velocity dispersion. Their size─line width relation shows a power-law slope of 0.58, comparable to measurements for CMZs in other galaxies and suggestive of significant contribution from ordered motion on large scales. We further decompose the observed velocity dispersion in each gas structure into ordered versus random motions. The former appears stronger in gas structures at ≳30 pc, while the latter becomes more dominant at ≲30 pc. Modulo uncertainties with the CO-to-H₂ conversion factor, the estimated gravitational free-fall time is comparable to the crossing time of ordered motions for structures on all spatial scales, and both become longer than the crossing time of random motions at small, ≲10 pc scales. Our results highlight the varying sources and drivers of gas motions on different spatial scales in the CMZ of a Milky Way─like galaxy.

ALMA [C I] Image of the Circumnuclear Disk of the Milky Way: Inflowing Low-density Molecular Gas

First Author: Tanaka, Kunihiko
Instruments: ALMA_Band_3, ALMA_Band_8
ProgramIDs: 2013.1.00857.S, 2015.1.01040.S, 2016.1.00940.S, 2022.1.01219.S
BibCode: 2026ApJ...999..185T

We present Atacama Large Millimeter/submillimeter Array [C I] ³P₁─³P₀ imaging of the central 6.6 × 4.2 pc² region of the Galaxy encompassing the circumnuclear disk (CND). The data reveal low-density ( nH2∼103 cm⁻³) molecular gas with inward motion, widespread both inside and outside the CND. The normalized [C I] to CS 7─6 intensity difference decreases inwardly from R = 4 pc to 1.7 pc and azimuthally along the CND's rotation, likely tracing paths of low-density gas inflow. By projecting spaxels into orbital coordinates assuming a velocity field model, we identify four kinematic features: a pair of spiral outer streamers toward the CND, inner streamers extending to 0.5 pc from Sgr A^*, an outer disk at R ∼ 3─6 pc, and the rotating ring at R = 2 pc. P─P─V correlation between the inner streamers and H42α indicates gas supply to the mini-spiral through the western arc (WA) and northern arm (NA). The total inflowing mass is 1.5 × 10⁴ M_⊙, 1.7 times the mass of the rotating ring. The identified flows can be organized into two main pathways connecting the CND exterior and interior: "WA flow" feeding the mini-spiral WA via the CND, and "NA flow" bypassing the purely rotating orbit. The inflow rate along the former is approximately constant (0.1─0.16 M_⊙ yr⁻¹), implying a CND dwelling time comparable to its orbital period and supporting the CND's transient nature. We also identify two [C I]-bright clumps (CBCs) lacking dense-gas counterparts near the contact point between the northern outer streamer and the CND. Apparently intact against tidal disruption despite subcritical densities, the CBCs may represent a chemically young phase shortly after formation in colliding flows.

Breathless BEARS: [O III] 88 µm emission of dusty star-forming galaxies at z = 3−4

First Author: Bakx, T. J. L. C.
Instruments: ALMA_Band_10, ALMA_Band_7, ALMA_Band_8, ALMA_Band_9
ProgramIDs: 2021.1.00265.S, 2022.1.00145.S, 2022.1.00432.S, 2023.1.00750.S
BibCode: 2026MNRAS.546ag106B

We present [O III] 88

$\mu {\rm m}$

observations towards four Herschel-selected dusty star-forming galaxies (DSFGs;

$\log _{10} \mu L_{\rm IR} / L_{\odot } = 13.5 \!-\! 14$

$z = 2.9\!-\!4$

) using the Atacama Compact Array (ACA) in Bands 9 and 10. We detect [O III] emission in all four targets at

$\gt\, 3 \sigma$

, finding line luminosity ratios (

$L_{\rm [O_{III}]} / L_{\rm IR} = 10^{-4.2}$

$10^{-3}$

) similar to local spiral galaxies, and an order of magnitude lower when compared with local dwarf galaxies as well as high-redshift Lyman-break galaxies. Using the short-wavelength capabilities of the ACA, these observations bridge the populations of galaxies with [O III] emission at low redshift from space missions and at high redshift from ground-based studies. The difference in [O III] emission between these DSFGs and other high-redshift galaxies reflects their more evolved stellar populations (>10 Myr), larger dust reservoirs (

$M_{\rm dust} \sim 10^{9 - 11}$

$_{\rm \odot }$

), metal-rich interstellar medium (

$Z \sim 0.5\!-\!2$

$_{\odot }$

), and likely weaker ionization radiation fields. Ancillary [C II] emission on two targets provide

$L_\mathrm{[O\, {\small III}]}/L_\mathrm{[C\, {\small II}]}$

ratios at 0.3─0.9, suggesting that ionized gas represents a smaller fraction of the total gas reservoir in DSFGs, consistent with theoretical models of DSFGs as transitional systems between gas-rich, turbulent disks and more evolved, gas-poor galaxies. Expanding samples of DSFGs with [O III] emission will be key to place this heterogeneous, poorly understood galactic phase in its astrophysical context.

Methanol Line Diagnostics of Post-burst Physical Evolution in the High-mass Episodic Accretion Source G358.93−0.03

First Author: Liu, Meizhu
Instruments: ALMA_Band_5, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2018.A.00031.T, 2019.1.00768.S, 2021.1.00799.S
BibCode: 2026ApJ..1000...30L

We report multi-epoch Atacama Large Millimeter/submillimeter Array Band 5─7 observations of the high-mass episodic-accretion burst source G358.93−0.03, covering (sub-)millimeter CH₃OH masers, quasi-thermal lines, and continuum from 2019 April to 2022 January. Five new CH₃OH maser transitions (189.369, 220.401, 241.043, 293.464, and 330.794 GHz) were detected, all coincident with the brightest continuum core MM1. Together with nine previously known sub-millimetre masers, they exhibit a rapid intensity decline on 3 month timescales from 2019 April to July. In 2019 April, the maser spots form a ring-like pattern, matching the morphology of centimeter-wavelength counterparts observed in previous studies. Rotation diagram analysis of quasi-thermal CH₃OH lines reveals pronounced post-burst evolution in the gas envelopes of MM1 and MM3: both cores were heated due to the heat wave propagation induced by the episodic accretion from MM1 in 2019 October. These results establish that episodic accretion bursts in massive protostars trigger rich (sub)millimeter maser activity and drive radiative heat waves across their natal environments.

A Chemistry-first Centered Icy Chemical Inventory of Protostellar Sources with JWST

First Author: Turner, Andrew M.
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.01792.S, 2017.1.00693.S, 2021.1.00357.S
BibCode: 2026ApJ..1000...17T

The chemical evolution in star forming regions is driven by the interplay between gas and ice mantles. Identifying the ice compositions at the early stage of star formation thus provides constraints on the chemical processes inaccessible from gas-phase characterizations. As part of the CORINOS program, spectra from the James Webb Space Telescope (JWST) Mid-Infrared Instruments Medium Resolution Spectroscopy were taken toward four Class 0 protostars: IRAS 15398-3359, Ser-emb7, L483, and B335. The spectra were processed with simultaneous fitting of a continuum and silicate absorption to produce optical depth mid-infrared spectra of the ices at 5─28 μm (360─2000 cm⁻¹) toward these four sources. Simple molecules such as water (H₂O), carbon dioxide (CO₂), methanol (CH₃OH), formic acid/formate (HCOOH/HCOO⁻), ammonia/ammonium (NH₃/NH₄⁺), and formaldehyde (H₂CO) are the most abundant features in these ices, while complex organic molecules (COMs) represent a smaller contribution. Likely COMs include hydroxylamine (NH₂OH), methylamine (CH₃NH₂), and ethanol (CH₃CH₂OH). Absorption features belonging to functional groups such as ─CH₃ and ─OH suggest that additional COMs are present, but these cannot be unambiguously assigned due to overlapping bands. Formation pathways toward these COMs utilizing radical─radical combination reactions based on laboratory simulation experiments is presented. By extension, COMs predicted by these reactions, but absent from the spectra, are discussed. The results provide insight into the chemical environment of these ices and also highlight the critical need for caution and sufficient evidence in order to confidently identify COMs in ice.

JWST Edge-on Disk Ice (JEDIce): Program Overview and Ice Survey Results

First Author: Bergner, Jennifer B.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2016.1.00771.S, 2022.1.01302.S, 2023.1.00634.S, 2023.1.00907.S
BibCode: 2026ApJ..1002...17B

The icy material within protoplanetary disks plays a central role in planet formation, yet remains poorly characterized by observations. We present 1.6─28 μm spectra of five disks obtained as part of the JWST Edge-on Disk Ice program, representing the largest survey of disk ices to date. The major ice species H₂O, CO₂, and CO are detected toward all disks, and exhibit a wide range of absolute optical depths and optical depth ratios across the sample. This is suggestive of a range of ice abundances and compositions, but quantitative constraints will require radiative transfer modeling. All disks exhibit ice features across the entire spatial region where the IR continuum is detected; vertically elevated ice grains therefore seem to be ubiquitous in disks. The CO ice is consistently dominated by apolar CO:CO₂ mixtures, implying that the disk ice compositions are neither completely reset nor pristinely inherited from the protostellar stage. The presence of these mixtures also suggests that entrapment may be important in shaping the spatial distribution of CO within the disks. Small molecules commonly seen in protostellar ices (CH₄, CH₃OH, and NH₃) are generally not detected in our sample, though tracers of ammonium salts (OCN⁻ and the 6.85 μm band) are common, potentially reflecting an evolution toward comet-like ice compositions. The spectra also contain a wealth of information about the micron-sized dust, atomic and molecular gas, and polycyclic aromatic hydrocarbon content, which together with the ice constraints will provide a comprehensive picture of the chemical, physical, and dynamical state of these systems.

Hadronic origin of the very high-energy gamma-ray emission from the low-luminosity AGN in NGC 4278

First Author: Shoji, Asahi
Instruments: ALMA_Band_6
ProgramIDs: 2022.1.01173.S
BibCode: 2026PASJ...78..166S

The Large High Altitude Air Shower Observatory has detected very high-energy (VHE) gamma-rays from NGC 4278, which is known to host a low-luminosity active galactic nucleus (AGN). Having only very weak radio jets, the origin of its VHE gamma-rays is unclear. In this paper we first show that NGC 4278 has a massive molecular cloud surrounding the nucleus by analyzing data taken with the Atacama Large Millimeter/submillimeter Array. We then assume that cosmic ray protons are accelerated in a radiatively inefficient accretion flow around the supermassive black hole, diffusing into the molecular cloud and producing gamma-rays and neutrinos via

$pp$

interactions. We model the gamma-ray spectra and find that the observations can be explained by such hadronic processes if the AGN activity was higher in the past than at present, and the diffusion coefficient in the molecular cloud is appreciably smaller than in the Milky Way interstellar medium. We also show that although the high-energy neutrinos co-produced with the gamma-rays are unlikely to be detectable even with IceCube-Gen2, the accompanying synchrotron X-ray emission due to pion-decay secondary electrons and positrons may be detectable in the future, providing a valuable test of our hadronic model.

Planetary-mass exosatellite detected around the substellar companion of a star

First Author: Hoy, Kevin
Instruments: CRIRES
ProgramIDs: 116.2AP9, 112.25HG, 114.271E
BibCode: 2026Natur.655..865H

Brown dwarfs occupy the mass regime between planets and stars. In systems containing both a star and a substellar companion (be it a brown dwarf or an exoplanet), a third object orbiting the companion can be called an exosatellite. Exoplanet satellites can be easily described as exomoons, but it is not clear if satellites of brown dwarf companions can be called the same, as the term lacks a formal definition. Despite more than 6,000 exoplanets being discovered¹, no exomoon has ever been confidently detected. Although there are candidates, they lack confirmation and remain controversial^{2, 3, 4─5}. In this work, we present evidence of an exosatellite orbiting the directly imaged brown dwarf companion CD-35 2722 B. Applying radial velocity analysis, the same technique used to discover the first exoplanet around a Solar-type star⁶, to VLT/CRIRES+ spectra of this brown dwarf, we find what appears to be the periodic signal of at least one orbiting satellite. This is the first time, to our knowledge, this technique has produced evidence of satellites around a companion brown dwarf. Our best-fitting model includes a satellite with a minimum mass of about 0.9 Jupiter masses and a period of around 170 days. Although it is uncertain whether this exosatellite will fulfil the presently undefined criteria for qualifying as an exomoon, it is a marked step towards that first uncontroversial detection, as advancing technology will allow the same method to be applied to less massive targets.

Magnetic fields in galactic environments probed by fast radio bursts

First Author: Khrykin, Ilya S.
Instruments: MUSE
ProgramIDs: 105.20HG, 110.241Y, 0104.A-0411
BibCode: 2026A&A...706A..11K

Fast radio bursts (FRBs) are extragalactic, bright, millisecond radio pulses emitted by unknown sources. FRBs constitute a unique probe of various astrophysical and cosmological environments via their characteristic dispersion (DM) and Faraday rotation (RM) measures that encode information about the ionised gas traversed by the radio waves along the FRB line of sight. In this work, we analysed the observed RM measured for 14 localised FRBs in the 0.05 ≲ z_frb ≲ 0.5 redshift range, in order to infer the total magnetic field, B, in various galactic environments. Additionally, we calculated f_gas ─ the average fraction of baryons in the ionised CGM. We built a spectroscopic dataset of FRB foreground galaxy halos, acquired with VLT/MUSE observations and by the FLIMFLAM collaboration. We developed a novel Bayesian statistical algorithm and used it to correlate information on the individual intervening halos with the observed RM_obs. This approach allowed us to disentangle the magnetic fields present in various environments traversed by the FRB sight lines. Our analysis yields the first direct FRB constraints on the strength of magnetic fields in the interstellar medium (ISM) ( B_host^local B host local ) and in the halos ( B_host^halo B host halo ) of FRB host galaxies, as well as in the halos of foreground galaxies and groups ( B_fg^halo B fg halo ). Assuming no field reversals, we find that the average magnetic field strength in the ISM of the FRB host galaxies is B_host^local = 5.4^1.1_−0.9μ B host local = 5 . 4 − 0.9 + 1.1 μ G. Additionally, we placed an upper limit on the average magnetic field strength in FRB host halos, B_host^halo ≲ 4.8 μ B host halo ≲ 4.8 μ G, and in foreground intervening halos, B_fg^halo ≲ 4.3 μ B fg halo ≲ 4.3 μ G. Moreover, we estimated the average fraction of cosmic baryons inside 10 ≲ log₁₀(M_halo/M_⊙) ≲ 13.1 halos to be f_gas = 0.45_−0.19^+0.21 f gas = 0 . 45 − 0.19 + 0.21 . We find that the magnetic field strengths inferred in this work are in good agreement with previous measurements. In contrast to previous studies that analysed FRB RMs and have not considered contributions from the halos of the foreground and/or FRB host galaxies, we show that halos can contribute a non-negligible amount of RM and must be taken into account when analysing future FRB samples.

Distribution of iron, oxygen, and sulfur in the direction of the outer arms of the Galaxy

First Author: Andrievsky, S. M.
Instruments: UVES
ProgramIDs: 105.20MX, 106.2129, 081.D-0928, 082.D-0901, 089.D-0767, 093.D-0816
BibCode: 2026A&A...705A.241A

Aims. We conducted a high-resolution spectroscopic study of 51 distant Cepheids located in the outer part of the Galactic disk in the direction of the Perseus Arm. The aim of this investigation is to search for a possible observational manifestation of the influence of spiral arms or other dynamical processes on the chemical properties in this region of low-density gas. Methods. The effective temperature for each Cepheid was obtained from the line-depth-ratio dependencies. Abundances of three chemical elements ─ oxygen, sulfur, and iron ─ were obtained. We used the local-thermodynamic-equilibrium (LTE) approximation for iron, and the nonlocal thermodynamic equilibrium (non-LTE) approximation for oxygen and sulfur. Results. The abundances of iron, oxygen, and sulfur in our program stars were plotted as a function of galactocentric distances determined using heliocentric distances based on parallaxes from Gaia DR3, corrected for parallax bias. The Locally Weighted Scatterplot-Smoothing (LOWESS) method was used for statistical analysis of the plotted dependencies. We found a clear sign of flattening of the radial abundance distribution (plateau-like structure) for the studied elements, starting at a galactocentric distance of approximately 14 kpc. Formally dividing the overall iron abundance distribution into two parts and applying a linear regression for each section yields the following results on the gradient: ─0.072 dex kpc⁻¹ for the 8─14 kpc range and ─0.006 dex kpc⁻¹ for the 14─22 kpc range, with a formal intercept at 14 kpc. Similar gradients were also found for sulfur. Conclusions. We believe this flattening is the result of the dynamical influence of the Perseus and other outer spiral arms on the global star formation processes in the gas disk at the outskirts of our Galaxy.

Mid-infrared interferometry of 23 AGN tori: On the significance of polar-elongated emission

First Author: Lopez-Gonzaga, N.
Instruments: MIDI, VISIR
ProgramIDs: 184.B-0832, 087.B-0266, 086.B-0919
BibCode: 2016A&A...591A..47L

Context. Detailed high-resolution studies of active galactic nuclei (AGN) with mid-infrared (MIR) interferometry have revealed parsec-sized dust emission that is elongated in the polar direction in four sources. Aims: Using a larger, coherently analyzed sample of AGN observed with MIR interferometry, we aim to identify elongated MIR emission in a statistical sample of sources. More specifically, we wish to determine if there is indeed a preferred direction of the elongation and whether this direction is consistent with a torus-like structure or with a polar emission. Methods: We investigated the significance of the detection of an elongated shape in the MIR emission by fitting elongated Gaussian models to the interferometric data at 12 μm. We paid special attention to (1) the uncertainties caused by an inhomogeneous (u,v) coverage; (2) the typical errors in the measurements; and (3) the spatial resolution achieved for each object. Results: From our sample of 23 sources, we are able to find elongated parsec-scale, MIR emission in five sources: three type 2s, one type 1i, and one type 1. Elongated emission in four of these sources has been published before; NGC 5506 is a new detection. The observed axis ratios are typically around 2 and the position angle of the 12 μm emission for all the elongated sources always seems to be closer to the polar axis of the system than to the equatorial axis. Two other objects, NGC 4507 and MCG-5-23-16, with reasonably well-mapped (u,v) coverage and good signal-to-noise ratios, appear to have a less elongated 12 μm emission. Conclusions: Our finding that sources showing elongated MIR emission are preferentially extended in polar direction sets strong constraints on torus models or implies that both the torus and NLR/outflow region have to be modeled together. In addition, models used for SED fitting will have to be revised to include emission from polar dust.

Locating the missing large-scale emission in the jet of M87* with short EHT baselines

First Author: Georgiev, Boris
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00841.V, 2019.1.01797.V
BibCode: 2026A&A...709A..26G

In very-long baseline interferometric arrays, nearly co-located stations probe the largest scales and typically cannot resolve the observed source. In the absence of a large-scale structure, closure phases constructed with these stations are zero and, since they are independent of station-based errors, they can be used to probe data issues. Here, we show how these trivial closure phases become nonzero with a brightness distribution on smaller scales than their short baseline would suggest. When applied to sources that are made up of a bright compact and large-scale diffuse component, the trivial closure phases directly measure the centroid relative to the compact source and higher-order image moments. We present a technique to measure these image moments with minimal model assumptions and validate it on synthetic Event Horizon Telescope (EHT) data. We then apply this technique to 2017 and 2018 EHT observations of M87^* and find a weak preference for extended emission in the direction of the large-scale jet. We also apply it to 2021 EHT data and measure the source centroid about 1 mas northwest of the compact ring, which is consistent with the jet observed at lower frequencies.

Improving the diameters of interferometric calibrators with MATISSE

First Author: Robbe-Dubois, S.
Instruments: MATISSE
ProgramIDs: 4103.L-0941
BibCode: 2022MNRAS.510...82R

A good knowledge of the angular diameters of stars used to calibrate the observables in stellar interferometry is fundamental. As the available precision for giant stars is worse than the required per cent level, we aim to improve the knowledge of many diameters using MATISSE (Multiple AperTure mid-Infrared SpectroScopic Experiment) data in its different instrumental configurations. Using the squared visibility MATISSE observable, we compute the angular diameter value, which ensures the best-fitting curves, assuming an intensity distribution of a uniform disc. We take into account that the transfer function varies over the wavelength and is different from one instrumental configuration to another. The uncertainties on the diameters are estimated using the residual bootstrap method. Using the low spectral resolution mode in the Lband, we observed a set of 35 potential calibrators selected in the Mid-infrared stellar Diameter and Flux Compilation Catalogue with diameters ranging from about 1 to 3 mas. We reach a precision on the diameter estimates in the range 0.6 per cent to 4.1 per cent. The study of the stability of the transfer function in visibility over two nights makes us confident in our results. In addition, we identify one star, 75 Vir initially present in the calibrator lists, for which our method does not converge, and prove to be a binary star. This leads us to the conclusion that our method is actually necessary to improve the quality of the astrophysical results obtained with MATISSE, and that it can be used as a useful tool for 'bad calibrator' detection.

The Identification of Two JWST/NIRCam-dark Starburst Galaxies at z = 6.6 with ALMA

First Author: Sun, Fengwu
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_5, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2017.1.00139.S, 2017.1.01532.S, 2019.1.00147.S, 2021.1.00443.S, 2022.1.01077.L
BibCode: 2026ApJ..1003..206S

We analyze two dusty star-forming galaxies at z = 6.6. These galaxies are selected from the ASPIRE survey, a JWST Cycle 1 medium program, and the Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 9 large program targeting 25 quasars and their environments at z ≃ 6.5─6.8. These galaxies are identified as companions to UV-luminous quasars and robustly detected in ALMA continuum and [C II] emission, yet they are extraordinarily faint at the NIRCam wavelengths (down to >28.0 AB mag in the F356W band). They are more obscured than galaxies like Arp220 (A_V up to ∼7.5 mag), and thus we refer to them as "NIRCam-dark" starburst galaxies (star formation rate ≃80─250 M_⊙ yr⁻¹). Such galaxies are typically missed by (sub)-millimeter blank-field surveys. From the star formation history (SFH), we show that the NIRCam-dark galaxies are viable progenitors of massive quiescent galaxies at z ≳ 4 and descendants of UV-luminous galaxies at z > 10. Although it is hard to constrain their number density from a quasar survey, we conclude that NIRCam-dark galaxies can be as abundant as n ∼ 10^−5.5 Mpc⁻³ assuming a light halo occupation model. If true, this would equal to ∼30% of the number densities of both the quiescent galaxies at z ≳ 4 and UV-luminous galaxies at z > 10. We further predict that analogs at z ∼ 8 should exist according to the SFH of early massive quiescent galaxies. However, they may fall below the current detection limits of wide JWST and ALMA surveys, and thus remain "JWST-dark." To fully trace the evolution of massive galaxies and dust-obscured cosmic star formation at z ≳ 8, wide-field JWST/NIRCam imaging and slitless spectroscopic surveys of early protoclusters are essential.

Constraining the magnetic field strength of a flaring radio core in the compact steep spectrum source 3C 138

First Author: Li, Shan
Instruments: ALMA_Band_3, ALMA_Band_4
ProgramIDs: 2011.0.00001.CAL
BibCode: 2026A&A...710A..63L

Context. Compact steep spectrum (CSS) sources generally show weak Doppler boosting, yet some exceptions show multi-year-scale radio flux variability and high-energy activity. Since 2022, the CSS quasar 3C 138 has been in a radio high state accompanied by multiple gamma-ray outbursts, offering unique opportunities to study changes in jet physical conditions. Aims. We estimated the synchrotron self-absorption (SSA) magnetic field (B_SSA) in the SSA core of 3C 138 during its high state and compared it with the equipartition magnetic field (B_eq) to assess the core field environment. Methods. Using extended Korean Very long-baseline interferometry Network (KVN) data at 22, 43, 86, and 129 GHz (2024─2025), we calibrated the visibilities and modeled resolved components with circular Gaussians. A single-zone SSA model fitted to the core spectrum provided the turnover frequency and peak flux density, from which we estimated the B_SSA and B_eq. We used Very Large Array and Atacama Large Millimeter/submillimeter Array data to constrain the broadband spectra with the same model. Results. The KVN SSA core shows a turnover at about 33 GHz and a peak flux of about 1.45 Jy. The inferred B_SSA is far below equipartition, with B_SSA/B_eq ≍ 0.05. Conclusions. The flux variability of 3C 138 is driven by a compact, particle-dominated core. Shock-driven particle injection in the inner jet could account for the core brightening and the production of X-ray/gamma-ray emissions through an inverse-Compton process without requiring extreme relativistic beaming effects.

First result with AMBER+FINITO on the VLTI: the high-precision angular diameter of V3879 Sagittarii

First Author: Le Bouquin, J.-B.
Instruments: AMBER
ProgramIDs: 60.A-9054
BibCode: 2008A&A...481..553L

Aims: Our goal is to demonstrate the potential of the interferometric AMBER instrument linked with the Very Large Telescope Interferometer (VLTI) fringe-tracking facility FINITO to derive high-precision stellar diameters. Methods: We use commissioning data obtained on the bright single star V3879 Sgr. Locking the interferometric fringes with FINITO allows us to record very low contrast fringes on the AMBER camera. By fitting the amplitude of these fringes, we measure the diameter of the target in three directions simultaneously with an accuracy of 25 micro-arcseconds. Results: We showed that V3879 Sgr has a round photosphere down to a sub-percent level. We quickly reached this level of accuracy because the technique used is independent from absolute calibration (at least for baselines that fully span the visibility null). We briefly discuss the potential biases found at this level of precision. Conclusions: The proposed AMBER + FINITO instrumental setup opens several perspectives for the VLTI in the field of stellar astrophysics, like measuring with high accuracy the oblateness of fast rotating stars or detecting atmospheric starspots. Based on observations collected at the European Southern Observatory, Paranal, Chile. Calibrated interferometric visibility points are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/481/553

MANGOS ─ II. Five new giant planets orbiting low-mass stars

First Author: Dransfield, G.
Instruments: ESPRESSO
ProgramIDs: 112.25ZF, 114.27JF
BibCode: 2026MNRAS.547ag448D

Giant planets orbiting low-mass stars on short orbits present a conundrum, as in the most extreme cases their existence cannot be reconciled with current models of core accretion. Therefore, surveys dedicated to finding these rare planets have a key role to play by growing the sample to overcome small number statistics. In this work, we present MANGOS, a programme dedicated to the search for giant objects (planets, brown dwarfs, and low-mass stars) orbiting M dwarfs. We report on the discovery of five new giant planets (TOI-3288 Ab, TOI-4666 b, TOI-5007 b, TOI-5292 Ab, TOI-5916 b) first detected by TESS, and confirmed using ground-based photometry and spectroscopy. The five planets have radii in the range of 0.99─1.12

$\mathrm{R_{Jup}}$

, masses between 0.49 and 1.69

$\mathrm{M_{Jup}}$

, and orbital periods between 1.43 and 2.91 d. We reveal that TOI-3288 and TOI-5292 are wide binaries, and in the case of TOI-5292, we are able to characterize both stellar components. We demonstrate that the planets presented are suitable for further characterization of their obliquities and atmospheres. We detect a small but significant eccentricity for TOI-5007 b, although for this to be more robust, more observations are needed to fully sample the orbit. Finally, we reveal a correlation between stellar metallicity and planet bulk density for giant planets orbiting low-mass stars.

Bar-driven gas redistribution suppresses star formation in spiral galaxies: Evidence from dust lanes in NGC 3351

First Author: George, K.
Instruments: ALMA_Band_6
ProgramIDs: 2012.1.00650.S, 2015.1.00956.S, 2017.1.00886.L
BibCode: 2026A&A...710L..30G

We present observational evidence, based on high-resolution imaging from HST, ALMA, and AstroSat/UVIT, that the redistribution of gas driven by the bar in the face-on spiral galaxy NGC 3351 results in suppressed star formation in its central regions. Dust and molecular gas coexist in galaxies, allowing dust lanes observed in galaxies to be used to probe the distribution of gas. In the central regions of NGC 3351, covered by the stellar bar, dust lanes are visible in the HST F438W─F814W colour map, but surprisingly, these areas lack molecular gas and recent star formation. The inward orientation of the dust lane morphology towards the galaxy's centre suggests that molecular gas was once present in this region but was redistributed to the centre due to the stellar bar's action. The direction of the dust lanes therefore indicates the past inflows of gas towards the galaxy centre, with their morphology consistently oriented inwards along the bar. These findings support a scenario in which the stellar bar has efficiently channelled molecular gas into the nucleus, building the central reservoir while suppressing star formation along the bar.

A precessing jet from an active galactic nucleus drives gas outflow from a disk galaxy

First Author: Kader, Justin A.
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2017.1.01235.S, 2023.1.00499.S
BibCode: 2026Sci...391..911K

To reproduce observed galaxy properties, cosmological simulations require that massive galaxies experience feedback from active galactic nuclei, which regulates star formation within those galaxies. However, the energetics and timescales of these feedback processes are poorly constrained. We combined optical, infrared, submillimeter, and radio observations of the active galaxy VV 340a, which is hosting a low-power jet launched from a supermassive black hole at its center. We found that the jet undergoes precession, with a period of (8.2 ± 5.5) × 10⁵ years, and drives an outflow of gas at a rate of 19.4 ± 7.9 solar masses per year. The jet shocks the gas, producing highly ionized plasma that extends several kiloparsecs from the nucleus. The outflow ejects sufficient gas from the galaxy to influence its star-formation rate.

A Radially Broad Collisional Cascade in the Debris Disk of γ Ophiuchi Observed by JWST

First Author: Han, Yinuo
Instruments: ALMA_Band_7
ProgramIDs: 2022.1.00338.L
BibCode: 2026ApJ..1004..182H

The A1V star γ Oph, at a distance of 29.7 pc, is known from Spitzer imaging to host a debris disk with a large radial extent and from its spectral energy distribution to host inner warm dust. We imaged γ Oph with the James Webb Space Telescope (JWST)/Mid-InfraRed Instrument at 15 and 25.5 μm, revealing smooth and radially broad emission that extends to a radius of at least 250 au at 25.5 μm. In contrast to JWST findings of an inner small-grain component with distinct ringed structures in Fomalhaut and Vega, the mid-infrared radial profile combined with prior Atacama Large Millimeter/submillimeter Array imaging suggests a radially broad steady-state collisional cascade with the same grain size distribution throughout the disk. This further suggests that the system is populated by a radially broad planetesimal belt from tens of astronomical units or less to well over 200 au, rather than a narrow planetesimal belt from which the observed dust is displaced to appear broad. The disk is also found to be asymmetric, which could be modeled by a stellocentric offset corresponding to a small eccentricity of ∼0.03. Such a disk eccentricity could be induced by a mildly eccentric <10 M_Jup giant planet outside 10 au, or a more eccentric companion up to stellar mass at a few astronomical units, without producing a resolvable radial gap in the disk.

HyGAL: Characterizing the Galactic ISM with observations of hydrides and other small molecules: III. The absorption lines of [O I], CH, and OH

First Author: Kim, W.-J.
Instruments: ALMA_Band_3
ProgramIDs: 2019.1.00685.S
BibCode: 2026A&A...710A.301K

The HyGAL Stratospheric Observatory for Infrared Astronomy (SOFIA) legacy program aims to characterize the interstellar medium (ISM) in the Milky Way using hydrides, [C II], and [O I] absorption lines with the 2.7 m SOFIA telescope toward twenty-five submillimeter-bright Galactic star-forming regions. As part of HyGAL, we investigated correlations among the known H₂ tracers ─ CH and OH from SOFIA observations, and HCO⁺ and CCH from ancillary absorption line data from ground-based telescopes. We also examined the abundance variation of neutral atomic oxygen, [O I], observed in absorption. CH, OH, HCO⁺, and CCH all exhibit strong mutual correlations. OH in particular shows tight correlations with HCO⁺ and CCH, reflecting their linked chemical and physical pathways. Column density ratios among these H₂ tracers are consistent with previous measurements in local diffuse clouds and remain uniform across Galactic environments and velocity intervals. The gas phase oxygen abundance relative to total hydrogen, ⟨X(O)⟩ = N(O)/N(H_total), is (3.09 ± 0.64) × 10⁻⁴, which is slightly below the elemental solar value but consistent with the previous observations measuring gas-phase abundances. We also find that N(H I) decreases toward the regions where the molecular fraction exceeds f_H₂^N ~ 0.5, marking the onset of the molecular phase. While the atomic oxygen abundance remains roughly constant, the abundances of OH, HCO⁺, and CCH increase with the molecular fraction. Gas traced by the HCO⁺ absorption corresponds to higher molecular fractions than that traced by H I and hydride ions, highlighting density variations in the diffuse-to-translucent ISM along different lines of sight.

Spectrally and Spatially Resolved (Sub)Millimeter HCN-to-HCO⁺ Flux Ratios in Nearby Ultraluminous Infrared Galaxies

First Author: Imanishi, Masatoshi
Instruments: ALMA_Band_4, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2017.1.00057.S, 2019.1.00027.S
BibCode: 2026ApJ..1004...39I

We present the results of our investigations of spectrally and spatially resolved (sub)millimeter HCN-to-HCO⁺ flux ratios at J = 2─1, J = 3─2, and/or J = 4─3 in 18 nearby (z < 0.15) ultraluminous infrared galaxies (ULIRGs), using ALMA ≲ 0 .″ 2 (≲ 500 pc) resolution data. The geometry of elevated HCN-to-HCO⁺ flux ratios (with >3σ detections for both molecular lines) in position-position-velocity (PPV) space is visually classified into (i) a spherical shell (spectrally and spatially distinct), (ii) spectrally distinct and spatially compact, and (iii) filled (spectrally filled and spatially compact). These can naturally be explained by the elevation of the flux ratio due to (i) a spatially resolved outflow, (ii) an active galactic nucleus (AGN) and/or a spatially unresolved outflow with blueshifted and redshifted emission components, and (iii) an AGN and/or a spatially confined outflow with not clearly separated blueshifted and redshifted velocity components, respectively. Signatures of elevated HCN-to-HCO⁺ flux ratios originated from (a) spatially resolved outflow and (b) AGN and/or spatially unresolved outflow are seen in seven and nine ULIRGs, respectively. In the former spatially resolved outflow-origin case, modest-velocity components relative to the maximum outflow velocity tend to be probed by spaxels with elevated HCN-to-HCO⁺ flux ratios. The spectrally and spatially resolved HCN-to-HCO⁺ flux ratios can provide additional information on the physical origin of the elevated flux ratios in nearby ULIRG nuclei compared to previously conducted spatially integrated and/or velocity-integrated analyses.

From gas to stars along the spiral wave: CO, HCN, and star formation variations across the spiral arms in NGC 4321 and M51

First Author: Greve, Minou
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2015.1.00956.S, 2017.1.00815.S
BibCode: 2026A&A...710A.121G

Context. Molecular clouds form stars from the interstellar medium via gravitational collapse, following a sequence from low-density gas to high-density cores and eventually the formation of stars. In classical density wave theory, gas clouds orbiting the galaxy experience gas compression and triggered star formation, while encountering the gravitational well of spiral arms. Aims. We aim to trace these different phases of the molecular cloud life cycle via tracers of molecular gas (CO), dense molecular gas (HCN), and star formation (Hα, 24 μm) within the spiral arms of two grand-design spiral galaxies: NGC 4321 and M51 (NGC 5194). Methods. In the spiral arms of these galaxies, we investigate the relation between molecular gas, dense gas, and star formation (CO-HCN-SFR) at matched physical resolutions of 270 pc and 125 pc in NGC 4321 and M51, respectively. We employed spiral arm masks for these galaxies and investigate trends of HCN/CO and SFR/HCN (SFR/CO), which serve as proxies for the dense gas fraction and dense (molecular) gas star formation efficiency, perpendicular to the spiral arm spines. Results. We find that HCN/CO, SFR/CO, and SFR/HCN increase from the upstream towards the downstream side of both spiral arms of NGC 4321, while their trends are less prominent in M51. Conclusions. Our results indicate that large-scale galactic dynamics (e.g. density waves) can induce a sequence of gas density and star formation-to-gas density variations perpendicular to the spiral arms. This sequence contributes to the increased scatter seen among spectroscopic ratios such as HCN/CO and SFR/HCN at sub-kiloparsec scales.

The multi-wavelength vertical structure of the archetypal β Pictoris debris disk

First Author: Han, Yinuo
Instruments: ALMA_Band_6, ALMA_Band_7, VISIR
ProgramIDs: 095.C-0425, 2012.1.00142.S, 2019.1.00041.S
BibCode: 2026A&A...711A..42H

Context. Thermal imaging of debris disks is resolving the vertical height in an increasing number of systems, enabling the use of the vertical structure to decode the dynamical state of the planetary system. Aims. In this study, we examine the multi-wavelength structure of the archetypical edge-on debris disk of β Pic, extensive imaging of which across mid-infrared to millimetre wavelengths makes it the prime system with which to study the vertical height across different grain size populations. Methods. We non-parametrically modelled the radial profiles and constrained the vertical height at each wavelength while taking into account the vertical warping, finding the disk to be on average 1.5 times thicker vertically in the mid-infrared compared to the millimetre and the scale height to be relatively constant across the radius. Results. The decreasing scale height with wavelength is in contrast to predictions from collisional damping, and could be a result of the combined effect of radiation pressure and random collisions. We also show that the disk is warped at millimetre wavelengths and find tentative evidence of clumps in ALMA images, confirmation of which will require follow-up observations. Conclusions. The millimetre vertical warping is consistent with findings in scattered light and the secular perturbation interpretation due to the inner giant planets, which could also explain the relatively constant apparent scale height across radius, and potentially earlier findings of a non-Gaussian vertical profile that this study confirms.

FAUST: XXXI. Grain properties and variability of three sources in GSS 30

First Author: Yang, Q.
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2018.1.01205.L
BibCode: 2026A&A...711A.117Y

Aims. To advance our understanding of dust properties in class 0/I young stellar objects, it is essential to resolve and characterize their structures at multiple wavelengths and investigate how both grain growth and environmental factors shape their spectral properties. Methods. We present 0.″5 angular resolution ALMA observations of the GSS 30 complex at 1.2─3.0 mm, collected as part of the FAUST large programme, with a linear resolution of 69 au. We analysed the dust continuum emission and performed model fitting to constrain the dust mass and the disk structure. Results. For IRS3, the spectral index increases radially from 2.0 at the centre to 2.5 at the disk edge. In contrast, it decreases from 2.0 to as low as 1.6─1.8 along the outflow direction. An asymmetric distribution shows α as low as 1.6 to the northeastern blueshifted lobe, possibly due to cold outer envelope dust obscuring warmer inner regions. Spectral energy distribution fitting indicates maximum dust grain sizes of tens of microns and a dust mass of 650─1510 M_⊕. IRS1 is connected with an extended structure to the north-east. It may be an outflow─disk complex or a trailing structure associated with a circumbinary disk, although we cannot rule out the possibility that it could also be a gas streamer accreting onto IRS1. At the centre of IRS1, the spectral index is <0.8, which is consistent with marginally optically thick free-free emission. IRS2 exhibits brightness variations over 420 seconds of observation, with a multi-epoch comparison suggesting a flare lasting tens of minutes, indicating magnetic activity in the central star. Conclusions. This study presents a detailed millimetre multi-wavelength analysis of the GSS 30 IRS3 and IRS1 systems, highlighting the crucial role of environmental factors ─ specifically dust obscuration and the connecting streamer structures ─ in shaping the observed morphology of these early-stage disks. We also find that the IRS2 exhibits millimetre variability, which may originate from magnetic flares at the surface of the protostar.

A New Framework for Multiline Analysis Combined Kernel Principal Component Analysis and Kernel Shapley Additive Explanations: A Case of NGC 1068 ALMA Band 3 Data

First Author: Okubo, Hiroma
Instruments: ALMA_Band_3, ALMA_Band_8
ProgramIDs: 2011.0.00061.S, 2012.1.00657.S, 2013.1.00060.S, 2015.1.00960.S, 2017.1.00586.S, 2018.1.01506.S, 2018.1.01684.S, 2019.1.00130.S
BibCode: 2026AJ....172...13O

We present a new framework for multiline analysis that combines kernel principal component analysis (Kernel PCA), an unsupervised machine learning method, and Kernel Shapley Additive Explanations (SHAP), an explainable artificial intelligence technique. To enable a comparison with PCA-based studies, which have been widely used in multiline analyses, we apply our framework to integrated intensity maps of 13 molecular lines from Atacama Large Millimeter/submillimeter Array Band 3 archival data of the nearby galaxy NGC 1068. Previous PCA-based studies of NGC 1068 reported that physically meaningful structures are mainly captured up to the second component. In contrast, our framework suggests that the features up to the third component are physically meaningful, whereas the physical meaning of the fourth component still requires further discussion. Furthermore, by comparing the results obtained from our framework with molecular column densities derived from local thermodynamical equilibrium analysis, we suggest that the abundance of HCO⁺ may be relatively enhanced in the molecular outflow region extending to a radius of about 400 pc from the galactic center, likely due to the effects of ultraviolet radiation and highly dense gas. These results show that our framework can provide data-driven insights into physical and chemical features that have not been clearly identified in previous studies. It also provides an efficient tool for interpreting the rapidly increasing amount of multiline observational data.

Survival of Molecular Complexity under Recent Supernova Feedback: Detection of Hot Cores in RX J1713.7−3946

First Author: Shimonishi, Takashi
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2024.1.00402.S
BibCode: 2026ApJ..1005..142S

Protostellar cores located near supernova remnants (SNRs) are considered potential analogs of the birth environment of the solar system. However, the extent to which supernovae influence their chemical evolution remains unclear. We report the first detection of hot molecular cores in an SNR using the Atacama Large Millimeter/submillimeter Array. The detected hot cores (HC1 and HC2) are located inside the X-ray shell of the young SNR RX J1713.7−3946, and both sources are associated with Class I intermediate-mass protostars. This paper focuses on a detailed chemical analysis of HC1, in which a variety of carbon-, oxygen-, nitrogen-, sulfur-, and silicon-bearing species are detected. Excitation analyses indicate that HC1 harbors dense (∼10⁷ cm⁻³), compact (<500 au), and high-temperature (≳100 K) molecular gas. Despite being located within a supernova-feedback region, the column density ratios of complex organic molecules (HCOOCH₃/CH₃OH, CH₃OCH₃/CH₃OH, and CH₃CHO/CH₃OH), a deuterated molecule (CH₂DOH/CH₃OH), and sulfur- and nitrogen-bearing species (OCS/CH₃OH and C₂H₅CN/CH₃CN) in HC1 are indistinguishable from those observed in hot cores/corinos in more typical star-forming environments. HC1 is located near the outer edge of the supernova shell, and the surrounding region has likely begun to be exposed to such a harsh environment only recently. The elapsed time since the onset of exposure to high-energy particles and photons may be too short for the chemical composition of the hot core to be significantly altered, and/or the hot core region may be shielded by magnetic fields amplified by supernova feedback, which could suppress the penetration of enhanced cosmic rays.

Charting circumstellar chemistry of carbon-rich asymptotic giant branch stars: III. SiO and SiS abundances

First Author: Unnikrishnan, R.
Instruments: ALMA_Band_3, ALMA_Band_6, ALMA_Band_7, PI230, SEPIA, SHFI
ProgramIDs: 2013.1.00070.S, 2013.1.00432.S, 2015.1.01271.S, 2017.1.00595.S, 096.F-9336, 098.F-9303, 094.F-9318, 087.F-9319, 0104.F-9305, 0107.F-9310
BibCode: 2026A&A...709A.216U

Context. The circumstellar envelopes of AGB stars are sites of rich molecular chemistry. The present understanding of C-rich AGB chemistry largely relies on observations of the archetypal carbon star IRC+10 216. Current molecular abundance estimates for carbon stars are based either on single-dish spectra sampling a range of excitation conditions, or on interferometric mapping of a few lines. Aims. We aim to estimate the circumstellar abundances of SiO, SiS, and their most abundant isotopologues (²⁹SiO, ³⁰SiO, ²⁹SiS, ³⁰SiS, and Si³⁴S) for a sample of five carbon stars. This study compares molecular abundances across the sources, tests chemical modelling predictions, and examines whether IRC+10 216 is representative of the broader carbon star population. Methods. We derived molecular abundances using detailed 1D non-local thermodynamic equilibrium (non-LTE) radiative transfer (RT) modelling, constrained by both morphological and excitation information obtained from spatially resolved ALMA maps and single-dish observations. We further compared the derived abundances to chemical modelling results. Results. We obtain good fits to the SiO and SiS line profiles, and derived well-constrained abundance profiles and reliable isotopic ratios for all sources except AFGL 3068. While the SiS peak abundances are very similar across the sample (2.0 × 10⁻⁶─4.7 × 10⁻⁶), we find that the SiO peak abundances of the rest of the stars are a factor of ~5 larger than that of IRC +10 216. The e-folding radii (R_e) are in the range 1.3 × 10¹⁶ − 7.0×10¹⁶cm for SiO and 6.0 × 10¹⁵ − 1.0×10¹⁷ cm for SiS. The R_e increases with gas density for both SiO and SiS. Our RT models cannot simultaneously fit the low- and high-J SiO lines of IRC+10216. Chemical models reproduce the derived SiO abundance profiles well, while over-predicting the SiS R_e values. Conclusions. Our models highlight the necessity of having spatially resolved observations across a broad range of excitation conditions to robustly constrain molecular abundance profiles, while also making evident the limitations inherent in 1D RT modelling using simplified (circum)stellar models. We find that the currently assumed SiS photodissociation rate in chemical models is underestimated.

A Redshift-based Red Selection of Dusty Star-forming Galaxies

First Author: Barger, A. J.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2013.1.00999.S, 2015.1.01425.S, 2017.1.01219.S, 2018.1.00035.L, 2021.1.00024.S, 2022.1.00073.S, 2023.1.00468.S
BibCode: 2026ApJ..1004..241B

We use JWST observations (1.5─4.44 μm), together with complete Atacama Large Millimeter/submillimeter Array (ALMA) observations (870 μm and/or 1.2 mm), of the massive lensing cluster field A2744 to show that galaxies between z = 1.5 and z = 5.5 with rest-frame red colors f_J/f_V > 3 correspond to dusty star-forming galaxies (DSFGs), little red dots (LRDs), and quiescent galaxies. The color selection picks out 34 of the 41 >4.5σ ALMA sources in the field (83%). We find that the luminous (rest-frame L_ν(1.22 μm) > 3.6 × 10²⁹ erg s⁻¹ Hz⁻¹) red sources are generally extended, while the less luminous red sources are almost all compact and correspond to the LRD population. We also find that the great majority of the luminous, extended red sources are DSFGs based on the ALMA data, with a small admixture of quiescent galaxies at z ≲ 3─4 that we identify based on their location in the rest-frame U − V versus V − J diagram. We do not detect any LRDs or quiescent galaxies at the >3σ level in the ALMA images. Roughly 10% of the DSFGs have high rest-frame X-ray luminosities (here L(8─28 keV) > 2.5 × 10⁴³ erg s⁻¹) and must be dominated by active galactic nuclei. The DSFGs and quiescent galaxies nearly all have M_* > 10¹⁰ M_⊙. These massive galaxies become rare at z > 5, paralleling the falloff in the number of detected DSFGs.

JWST's First View of the Most Vigorously Star-forming Cloud in the Galactic Center: Sagittarius B2

First Author: Budaiev, Nazar
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2013.1.00269.S, 2016.1.00550.S, 2017.1.00114.S
BibCode: 2026AJ....172...51B

We report JWST NIRCAM and MIRI observations of Sgr B2, one of the most active sites of star formation in the Galaxy. These observations, using 14 filters spanning 1.5─25 μm, have revealed a multilayered and highly structured cloud that contains both a revealed, low-extinction and hidden, high-extinction population of massive stars. JWST has detected new candidate H II regions around massive stars previously missed by radio telescopes. MIRI has detected radiation escaping from the forming massive cluster Sgr B2 N along its outflow cavities, demonstrating that infrared radiation finds geometric escape routes even in the densest, most heavily embedded regions in the universe. JWST further highlights the gas asymmetry in the cloud, showing a sharp, straight cutoff along the eastern cloud edge. Despite the great sensitivity of these observations, no extended population of young stellar objects has been detected, placing a limit on their minimum extinction; this result hints that star formation has only just begun in the cloud. Together, these results suggest that, despite already holding the crown for one of the most actively star-forming clouds, we have underestimated the total star formation in Sgr B2. JWST unveils previously hidden massive stars and ionized structures, offering the clearest view yet of how stars form under some of the most extreme Galactic conditions.

New ¹²C/¹³C and ¹⁴N/¹⁵N isotopic ratios measurements in HCN in the Jupiter stratosphere revealed by ALMA

First Author: Lefour, C.
Instruments: ALMA_Band_7
ProgramIDs: 2016.1.01235.S
BibCode: 2026A&A...710A.343L

Context. The collision of comet Shoemaker-Levy 9 (SL9) with Jupiter in 1994 changed the chemical composition of the Jovian stratosphere for decades. New molecules were detected minutes after the impacts (HCN, CO, H₂O, CS, etc.) and some are still present today. They were deposited in the stratosphere at pressures lower than 0.1 mbar and were most probably formed by shock-induced chemistry recombining Jovian and cometary material. However, the question of the origin of these molecules is still not completely understood. One way to address this open question is to determine the isotopic composition of the new molecules. Isotopic ratios have long been measured in the Solar System. They present a variety of values depending on the object or the molecule and therefore trace different reservoirs of material. Derivations of carbon and nitrogen isotopic ratios in HCN four years after SL9 showed atypical depletions in the heavier isotopes that had never been observed before in the Solar System. These results suggested an unusual cometary composition or an unknown fractionation mechanism in the hot and shocked air parcels. Aims. We aim to measure carbon and nitrogen isotopic ratios in HCN to shed light on the puzzling results of 1998. Methods. With Atacama Large Millimeter/submillimeter Array data from 2017 and radiative-transfer calculations, we derived the abundance of two HCN isotopologues, H¹³CN and HC¹⁵N, at pressures probed from 0.03 to 1.8 mbar. Results. We find ¹²C/¹³C = 73 ± 5 and ¹⁴N/¹⁵N = 245 ± 29, respectively (0.76─0.87) and (0.80─1.00) times the terrestrial references, and (0.69─0.87) and (0.42─0.70) times the solar-Jovian bulk values. In contrast to the strong depletions reported in 1998, our values are instead compatible with an enrichment in the heavier isotopes relative to the Jovian bulk. Conclusions. We interpret these enrichments as the direct signature of the cometary contribution in HCN and/or as 23 years of chemical evolution in the Jovian atmosphere.

The intrinsic dispersion of elemental abundance ratios in nearby metal-poor halo stars

First Author: Nissen, P. E.
Instruments: UVES
ProgramIDs: 67.D-0106, 073.D-0024
BibCode: 2026A&A...711A..49N

Context. Elemental abundance ratios in halo stars provide information on nucleosynthesis, chemical evolution, and accretion of dwarf galaxies at early times in the Milky Way because these ratios depend on the initial mass function (IMF) of core-collapse supernovae (CC SNe) and on the role of Type Ia SNe in making the elements. Aims. By determining very precise stellar parameters and abundances for a sample of intermediate-metallicity halo stars, we aim to estimate the intrinsic dispersion of various abundance ratios. Methods. We determined differential abundances of C, O, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, and Zr from high signal-to-noise VLT/UVES spectra for 25 turnoff stars with −2.4 < [Fe/H] < −1.3. Effective temperatures were obtained from profiles of the Hβ line and surface gravities from Gaia parallaxes. The spectral analysis was based on 1D model atmospheres assuming local thermodynamic equilibrium (LTE), but we applied 3D non-LTE corrections for several elements. Results. The dispersion in linear fits to the [X/Fe]-[Fe/H] relations is around a factor of two smaller than that found in previous studies. After correction for measurement errors, the 1σ intrinsic dispersion of [X/Fe] at a given metallicity is 0.09 dex for Y and Zr, 0.05-0.07 dex for C, O, and Al, 0.03-0.05 dex for Mg, Ca, Sc, Ti, V, Mn, and Zn, and <0.03 dex for Cr, Co, and Ni. We find strong correlations between the residuals in the [X/Fe]-[Fe/H] fits for the α-capture elements (Mg, Al, Ca, Sc, and Ti) and between the residuals for Y and Zr. Conclusions. Correlations between the residuals in the [X/Fe]-[Fe/H] fits and the effective temperature can be explained by differential atomic diffusion between elements, but its contribution to the scatter of [X/Fe] is of minor importance. Both stochastic effects in sampling the IMF of CC SNe and differences in the Type Ia to CC SNe enrichment ratio between star-forming regions are likely required to explain the intrinsic dispersion of [X/Fe].

Spectroscopic Characterization of Young Stellar Populations and Their Feedback in NGC 5253

First Author: Hernandez, Svea
Instruments: MUSE
ProgramIDs: 095.B-0321
BibCode: 2026ApJ..1005..198H

We present the spectroscopic analysis of far-ultraviolet (FUV) observations taken with the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) targeting young massive clusters in the nearby, metal-poor, blue compact dwarf galaxy NGC 5253. We characterize the stellar populations observed across seven COS pointings and report on their inferred physical parameters: age, metallicity, mass, and reddening values. Comparisons between our spectroscopic ages and those inferred using photometric methods show that the former are preferentially younger. We also investigate the impact of these young massive clusters on their surrounding interstellar medium. Using Very Large Telescope/MUSE optical observations and matching the size of the COS aperture, we measure outflow velocities of the ionized gas along the line of sight of the COS pointing with values ranging from ∼125 to 300 km s⁻¹. We report on strong statistically significant correlations between the outflow velocities and stellar ages, masses, and total mechanical luminosity primarily driven by supernovae (SNe) as derived from our full-spectrum fitting analysis. Although theoretical models predict a delayed injection of mechanical energy and momentum in low-metallicity environments (<0.4 Z_⊙), our study shows that in this particular system (Z ∼ 0.3 Z_⊙), feedback from SNe appears evident at the nominal >5 Myr ages, with no apparent delay. One possible explanation is that the decrease and suppression of mechanical feedback due to SN explosions might be dominant at even lower metallicities than those observed in NGC 5253.

Mapping a Quasar Outflow from Parsec to Kiloparsec Scales: A Combined HST Absorption and VLT Emission Investigation

First Author: Sharma, Mayank
Instruments: KMOS
ProgramIDs: 115.283E
BibCode: 2026ApJ..1005..203S

Linking nuclear winds to galactic-scale outflows remains a major observational challenge in understanding the multiscale physics of active galactic nucleus feedback. Here we present Very Large Telescope KMOS integral-field spectroscopy and Sloan Digital Sky Survey observations of the z = 0.9655 quasar PKS J0352−0711. Our analysis reveals complex, multi-ionization emission, including a fast, unresolved nuclear wind and a spatially resolved galactic-scale outflow. We integrate the [O III] emission properties with those deduced from the minibroad-absorption-line outflows detected in Hubble Space Telescope Cosmic Origins Spectrograph observations of this quasar. This unique combination of datasets allows us to trace, for the first time, the physical progression of a quasar outflow from ∼10 pc to 10 kpc. The multiscale kinematics support a unified evolutionary scenario where the inner, constant-velocity (∼−3800 km s⁻¹) expansion of the wind is traced jointly in absorption (∼9 pc) and emission (≳40 pc). As the wind propagates to ∼500 pc, the intermediate absorption system reveals a deceleration to ∼−2100 km s⁻¹, consistent with mass loading from the interstellar medium. Finally, our spatially resolved observations capture the gas breaking out of the inner galaxy, in the form of a wide-angle blueshifted outflow expanding beyond 8 kpc, with a velocity of ∼−1000 km s⁻¹. Despite the 3 orders-of-magnitude variation in spatial scale, and a factor of 4 deceleration, the momentum fluxes remain consistent within uncertainties across all scales. These results suggest that the distinct outflow components represent the integrated history of a sustained feedback cycle from nuclear to galactic scales.

Blobs and Blurs: A Citizen Science-identified Catalog of Diffuse Galaxies in the Fornax Cluster

First Author: Mazziotti, Nicolas
Instruments: OMEGACAM
ProgramIDs: 088.B-4012, 090.B-0414, 092.B-0744, 094.B-0496, 094.B-0512, 096.B-0501, 096.B-0582, 098.B-0208, 098.B-0298, 0100.B-0148, 0100.B-0168, 60.A-9038
BibCode: 2026ApJ..1005..207M

We present a catalog of 643 diffuse galaxies identified through a citizen science search of the Fornax cluster, of which we estimate 21.8% are nucleated (139/637; 6 inconclusive). This marks the first crowd-sourced effort to construct a cluster-scale census of diffuse galaxies. These objects were visually identified using a combination of the Fornax Deep Survey and Dark Energy Camera Legacy Survey imaging across 26 deg². Over 1400 volunteers cataloged the candidates within this sky area at a rate of 1.15 days deg⁻². Our catalog is highly complete relative to existing dwarf catalogs of Fornax (>80% of objects recovered) down to an effective radius r_eff = 5″, the minimum size we suggested volunteers classify, and to an effective r-band surface brightness as faint as <μ_r> ≃ 26 mag arcsec⁻². We detect 97 candidates that existing automated searches of Fornax did not find, and three candidates not found by any prior search, automated or visual. The stellar mass distribution of our sample is consistent with similar dwarf studies of Fornax, with the nucleated fraction peaking at 80% for a host galaxy mass of ∼10^8.5 M_⊙. The efficiency and completeness of our catalog thus establishes citizen science as a valuable tool for mapping diffuse galaxy populations in future sky surveys, such as the Legacy Survey of Space and Time.

Observational signatures and constraints on the intermediate neutron-capture process: The case of the carbon-enhanced metal-poor star TYC 6044−714−1 (RAVE J094921.8-161722)

First Author: Giribaldi, R. E.
Instruments: UVES
ProgramIDs: 114.27JT, 165.N-0276
BibCode: 2026A&A...711A..47G

Context. Observational abundances of carbon enhanced metal-Poor (CEMP) stars with patterns in between those produced by the rapid (r) and slow (s) nucleosynthesis processes (CEMP-rs stars) are currently invoked as evidence of synthesis via the intermediate (i) process in the early AGB evolutionary phase of metal-poor low-mass stars. Nevertheless, discriminating between r + s- and i-process hypotheses requires high-precision abundances obtained through advanced spectral modelling techniques. Theoretical models of the i-process have become more robust, incorporating refined stellar modelling and nuclear reaction physics, providing ranges of probable elemental abundances and isotopic ratio predictions to be confronted with observational determinations. Aims. We performed a new analysis of a high-resolution and high-signal-to-noise UVES spectrum of TYC 6044-714-1, one of the best-studied CEMP-rs stars. Methods. We derived accurate effective temperature (T_eff) and highly precise atmospheric parameters, element abundances, and isotopic ratios using state-of-the-art one-dimensional non-local thermodynamic equilibrium (1D non-LTE) and three-dimensional non-LTE (3D non-LTE) spectral line modelling. Using the latest AGB nucleosynthesis models computed with the FuNS evolutionary code, we assessed the possibility of the i-process to act aside the s-process. Results. We find that TYC 6044-714-1 was likely born as a normal in situ halo star about 13 Gyr ago, pre-enriched by the r process through a standard Galactic chemical-evolution pathway. Among the explored scenarios, the s + r model provides the best overall reproduction of the observed heavy-element abundance pattern and Ba isotopic ratios, yielding excellent agreement across all three s-process peaks. While i + s + r models with increasing overshooting efficiency improve the fit for specific elements ─ particularly Nb and those between the first and second neutron-capture peaks ─ they do not consistently reproduce the full abundance pattern. Conclusions. Although the i + s + r models achieve statistical fits comparable to the s + r case, they require extreme and physically implausible conditions, and predict s-process Ba fractions inconsistent with those inferred from isotopic ratios of the 4934 Å resonance line. We therefore conclude that the pure s + r scenario is the most plausible explanation.

VENUS: Strong-lensing Model of MACS J1931.8-2635: Revealing the Farthest Multiply Imaged Supernova

First Author: Allingham, Joseph F. V.
Instruments: MUSE, VIMOS
ProgramIDs: 095.A-0525, 186.A-0798
BibCode: 2026ApJ..1005..215A

We present a parametric strong-lensing model for the galaxy cluster MACS J1931.8-2635 (z_l = 0.35), accompanying the detection of the spectroscopically confirmed SN Eos at z = 5.13. We identify 10 new multiple-image systems in recent VENUS JWST/NIRCam imaging, so that the model is constrained with a total of 19 robust multiple-image systems—nine of which also have a spectroscopic redshift. For the point-like source corresponding to SN Eos, our model predicts a total of five images, with the observed radial image pair having a similar magnification of μ ≃ 25─30 and a small time delay of <5 days, in agreement with their simultaneous observation. According to the model, the other three predicted images arrived earlier, with time delays of 3.6 ± 0.7, 3.4 ± 0.7, and 53.9 ± 10.8 yr prior to the two observed images, and with magnifications of 14.5 ± 2.9, 11.9 ± 2.4, and 2.2 ± 0.4, respectively. The absence of detections at the predicted positions, where the host galaxy's images are also visible, confirms the transient nature of the source. SN Eos and its host galaxy are studied in separate articles, and we here focus on the lens model. The final model reaches a very good rms distance between model and observations of 0 .″ 44. We present the lens-modeling results, including newly identified systems such as a triply imaged, grand-design spiral galaxy candidate at z≃3.65−0.09+0.04 , and discuss the potential of using high-redshift lensed SNe for cosmography.

Spatially resolved broad-line region in a quasar at z = 4: Dynamical black hole mass and prominent outflow

First Author: Gravity+ Collaboration
Instruments: ERIS, GRAVITY
ProgramIDs: 114.27UV, 112.25M3
BibCode: 2026A&A...706A..99G

We present the first near-infrared interferometric data of a QSO at z = 4. The K-band observations were performed with GRAVITY+ on the VLTI using all four UTs, detecting a differential phase signal that traces the spatially resolved kinematics for both the Hβ and Hγ lines in the broad-line region (BLR). We fit the two lines simultaneously with an updated model that includes distinct rotating and conical outflowing components. For the best-fit model, more than 80% of the H I line emission from the BLR originates in an outflow with a velocity up to 10⁴ km s⁻¹. This is oriented so that our line of sight is along an edge of the conical structure, which produces the prominent blue wing on the line profile. A combination of anisotropic line emission and mid-plane opacity leads to the single-sided phase signal. The model is able to qualitatively match both the outflowing C IV line profile and the systemic O I fluorescent emission. The black hole mass of 8 × 10⁸ M_☉ that we derive is the highest redshift black hole mass measurement to date obtained directly from BLR dynamics. It is an order of magnitude lower than that inferred from various single epoch scaling relations, and it implies that the accretion is highly super-Eddington. With reference to recent simulations, the data suggest that this QSO is emitting close to its radiative limit in a regime where strong outflows are expected around a polar conical region.

ALMA Observations of Magnetic Fields in the Massive Star-forming Region IRAS 18360-0537

First Author: Mo, Shixian
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00793.S
BibCode: 2026AJ....172...75M

Assessing the significance of magnetic fields in high-mass star formation remains one of the most challenging topics in astrophysics. In this study, we present full polarization observations obtained from the Atacama Large Millimeter/Submillimeter Array of the high-mass star-forming region IRAS 18360-0537. The polarized dust emission at 1.3 mm reveals a clear hourglass-shaped morphology of the magnetic field. Interestingly, the magnetic field orientation is nearly perpendicular to both the outflow and core rotation axes, while it aligns with the elongation of the core. This orientation poses challenges for interpretation, particularly in light of the strong magnetic field strength estimated using the Davis─Chandrasekhar─Fermi method. Several scenarios provide insights into the underlying reasons for this magnetic field morphology. A clear velocity gradient seen in high-density tracing of molecular spectral lines indicates that the core is fast-rotating. The curved outskirts of the magnetic fields coincide with the outflow cavity, suggesting a possible influence from the outflow. The accretion flows along the core's elongation are also notable. Our study shows that the morphology of the magnetic field is probably highly influenced by the gas bulk motions.

The ALMA-QUARKS Survey: Investigating Thermal Feedback of Massive Protostars in Hot Molecular Cores

First Author: Meng, Dezhao
Instruments: ALMA_Band_6
ProgramIDs: 2021.1.00095.S
BibCode: 2026ApJS..285...29M

We identify a sample of 83 spatially resolved hot molecular cores (HMCs) in the Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures (QUARKS) survey, aiming at investigating thermal feedback from massive stars. Using CH₃CN (12─11) line emission together with 1.3 mm continuum data, we derive the radial temperature, volume density, and CH₃CN abundance profiles for the 83 HMCs. Based on the envelope temperature and density profiles, we compute the luminosities of the embedded massive protostars with the RADMC-3D radiation transfer model. The derived luminosities are comparable (within ∼1 dex) to the bolometric luminosities of their natal clumps and show strong correlations with several core-scale properties, including the HMC mass (Log[M_env] = 1.01 Log[L_⋆] − 4.80), the inner core radius (the flat radius of Plummer-like volume density profile) (Log[a] = 0.46 Log[L_⋆] + 0.52), and the central density (Log[n_c] = −0.55Log[L_⋆] + 10.47). These empirical relations provide useful observational constraints for physical models of protostellar objects. Importantly, we find a strong positive correlation between the massive protostellar luminosity and the local thermal Jeans mass. The derived Jeans masses, M_Jeans, exceed the HMC masses M_env, with the average M_Jeans being two times larger than the average M_env. This provides observational evidence that thermal feedback from massive protostars can effectively suppress further fragmentation of HMCs, thereby promoting massive star formation. In addition, the positive correlation between massive protostellar luminosity and natal clump mass suggests that more massive clumps preferentially host more luminous protostars, leading to stronger thermal feedback.

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): Formaldehyde (H₂CO) Emission and Its Links to Disk Properties

First Author: Chevalier, Ella
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2021.1.00128.L
BibCode: 2026ApJ..1005..199C

Protoplanetary disks are rotating structures of gas and dust surrounding young stars, serving as the birth places of planets. Understanding the chemical evolution of organic materials in these disks is key for tracing the origins of organics in planetary systems. Formaldehyde (H₂CO) is the most commonly detected organic molecule in protoplanetary disks. In this study, we investigate the emission of H₂CO and its link to disk properties, using a sample of 20 Class II disks in the Lupus and Upper Sco star-forming regions spanning over 1─6 Myr. We analyze the H₂CO lines at 218.222 and 290.623 GHz observed as part of the AGE-PRO ALMA Large Program. Within this sample we achieve a detection rate of H₂CO of 45% (9/20) and set robust upper limits for the nondetections. We measure the excitation temperature and column density of the H₂CO gas in the sources with H₂CO detections. We combine our sample with 13 additional disks with archival H₂CO detections and search for correlations between H₂CO properties and disk parameters. Notably, we find strong correlations between H₂CO line luminosity and dust radius, gas radius, dust mass, gas mass, stellar mass, and stellar luminosity. This suggests that H₂CO emission is brighter for extended massive dust disks where H₂CO can form via CO ice hydrogenation on grain surfaces. We find that the H₂CO excitation temperature is also correlated with stellar mass and stellar luminosity, so more-massive and -luminous stars could increase H₂CO excitation.

CO-dark Molecular Gas Traced by HCO⁺ in the Diffuse Interstellar Medium

First Author: Rybarczyk, Daniel R.
Instruments: ALMA_Band_3
ProgramIDs: 2018.1.00585.S, 2019.1.01809.S, 2015.1.00503.S
BibCode: 2026ApJ..1005..125R

A classic problem in the study of the interstellar medium (ISM) is the near-invisibility of molecular hydrogen (H₂) in cold environments. Observations of CO emission are typically used to indirectly trace H₂, but a significant fraction of H₂ in the diffuse ISM is not associated with any detectable CO emission ("CO-dark" molecular gas). Meanwhile, observations of HCO⁺ absorption trace nearly all of the H₂ in diffuse directions. In particular, a kinematically broad HCO⁺ absorption signature traces extremely diffuse, CO-dark H₂. We have used sensitive observations of HCO⁺, CO, and atomic hydrogen (H I) in absorption to constrain the properties of such diffuse molecular gas in five directions. The diffuse molecular gas revealed by broad HCO⁺ absorption has a lower fraction of cold H I ( fCNM=0.38−0.27+0.28 ) and a lower fraction of hydrogen in H₂ ( fmol=0.09−0.03+0.06 ) than gas traced by CO in the same directions. We detect almost no CO absorption from the gas traced by broad HCO⁺ absorption. We constrain the CO abundance relative to H₂ to be ≲10⁻⁶─10⁻⁵ for gas traced by both broad and narrow HCO⁺ absorption, consistent with chemical model predictions for the diffuse ISM. We further show that neither CO emission nor absorption is likely to be detected where N(H2) ≲ few × 10¹⁹ cm⁻²—a result of both the low CO abundance and the low H₂ column—while HCO⁺ absorption is readily detected for N(H2) ≳ few × 10¹⁸ cm⁻². These results demonstrate that even modest amounts of cold H I can bear H₂, providing critical constraints on the H I-to-H₂ transition in the ISM.

Direct Imaging Discovery of Giant Exoplanet β Pictoris d: A Decade-long Game of Hide-and-seek

First Author: Sutlieff, Ben J.
Instruments: ERIS, NACO, SPHERE
ProgramIDs: 084.C-0739, 072.C-0624, 116.28WQ, 284.C-5057, 088.C-0358, 086.C-0341, 090.C-0396, 095.C-0298, 094.C-0149, 096.C-0241, 0104.C-0418, 1100.C-0481, 60.A-9382, 60.A-9255
BibCode: 2026ApJ..1006L..10S

We report the direct imaging discovery of a third exoplanet in the β Pictoris (β Pic) system. We detect β Pictoris d (β Pic d) in noncoronagraphic observations obtained with the Very Large Telescope (VLT) Enhanced Resolution Imager and Spectrograph (ERIS), as well as multi-epoch archival datasets from the JWST Near Infrared Camera (NIRCam) and VLT/SPHERE. Astrometric measurements over an 11 yr baseline demonstrate that it is consistent with a gravitationally bound source with orbital motion. Joint multi-planet orbit fits of all three planets in the system yield a semimajor axis of 26.0−6.1+2.2 au and inclination 89.0−0.6+0.7 deg for planet d. β Pic d has a larger orbital semimajor axis than the other known planets in the system, but is coplanar with the inner two planets, and its orbit is consistent with sculpting the inner edge of the debris disk. β Pic d has a contrast of ∆L'=12.11±0.15 mag, with colors and luminosity that closely match those of 51 Eri b, another exoplanet in the β Pic moving group. Its VLT/ERIS and JWST/NIRCam colors are distinct from those of free-floating planetary-mass objects of a similar age and temperature. Its red F410M − F444W color indicates strong CO₂ absorption in its atmosphere and suggests significant enhancement in metals compared to free-floating objects. From the ATMO hot-start evolutionary models, we estimate an effective temperature of 600−60+45 K and mass of 2.4 ± 0.6 M_Jup, which also closely matches similar estimates for 51 Eri b. β Pic d is among the lowest-mass exoplanets imaged from the ground. This discovery highlights the deep sensitivity achievable with ground-based imaging in the mid-infrared and the discovery potential of future high-contrast observations with the Extremely Large Telescope.

Under the glare of a luminous quasar, the FIR continuum is still an excellent tracer of the ISM down to the central kiloparsec

First Author: Silverman, John D.
Instruments: ALMA_Band_5, ALMA_Band_9
ProgramIDs: 2023.1.00185.S, 2024.1.00596.S, 2022.1.00707.S
BibCode: 2026MNRAS.546ag167S

Contamination-free assessments of the interstellar medium and star formation in quasar host galaxies, particularly in the far-infrared, offer insights into the role of supermassive black holes in galaxy evolution. Motivated by simulations of quasar-heated dust on nuclear and galaxy-wide scales, we perform two-component (host galaxy + point source) modelling of high-resolution (

$\sim$

$0.1$

arcsec) Atacama Large Millimeter Array (ALMA) observations of the continuum in Band 5 (

$\lambda _{\mathrm{ rest}}$

$\sim 500~\mu m$

) of three luminous quasars (

$L_\mathrm{ {bol}}\sim 10^{47}$

erg s

$^{-1}$

) at

$z=2$

. For two quasars, we include Band 9 (

$\lambda _{\mathrm{ rest}}$

$\sim 154~\mu m$

; 0.06 and 0.3 arcsec) data, which further constrains the unresolved nuclear component. To break the degeneracy between quasar and stellar heating of dust on extended scales, we use CO (J = 5─4) to gauge the expected contribution of star formation to the infrared luminosity. We find very good agreement, between the strength and spatial distribution of the extended continuum and its prediction from CO (J = 5─4). This is supported by our three quasars following along the

$L_{\mathrm{ CO (5-4)}}-L_{\mathrm{ IR, SFR}}$

relation for inactive star-forming galaxies. As a consequence, there is no evidence for extended continuum emission that could be attributed to quasar-heated dust. As expected, the nuclear (i.e. torus) contribution is present and subdominant (e.g. 12 per cent in Band 9 for one quasar with a typical star-forming host) or non-existent (<8 per cent in Band 9 for the starburst). Substantial levels of star formation agree with previous estimates from unresolved ALMA observations, which find star formation rates consistent with star-forming main-sequence galaxies. Therefore, our results do not provide evidence for quasar-mode feedback, even in the most luminous cases.

Feeding the Dead: Neutral Gas Inflow in a Long-quenched Ancient Massive Galaxy at z ∼ 2.7 Observed with JWST/NIRSpec

First Author: Bevacqua, Davide
Instruments: ALMA_Band_6
ProgramIDs: 2022.1.00073.S
BibCode: 2026ApJ...997..189B

We report the spectroscopic detection of neutral gas inflow into a massive (M_* ≃ 4 × 10¹⁰ M_⊙) quiescent galaxy observed at z_spec = 2.6576 with the James Webb Space Telescope (JWST). From the redshifted absorption of the Na I doublet at λλ5890, 5896, we estimate an inflow velocity v=278−79+79 km s⁻¹ and a column density log(NNaI/cm2)=13.02−0.03+0.03 . We derive the inflowing mass of the gas Min=1.6−0.1+0.1×108M⊙ and rate Ṁin=19−7+6M⊙yr−1 . The presence of several surrounding galaxies suggests that the galaxy may be accreting gas from nearby companions. However, we cannot confirm this with current data, and the intergalactic medium or cosmic filaments are also viable sources of the inflowing gas. Despite the ongoing inflow, the galaxy remains quiescent, with an upper limit to the star formation rate of 0.2 M_⊙ yr⁻¹. Moreover, its star formation history suggests that the galaxy has remained quiescent during the past ∼1 Gyr, with half of its stars formed by redshift z50=11−3+18 . We discuss that the inflow is not massive, dense, or long-lived enough to ignite significant star formation (SF), or it is fueling low-level active galactic nucleus activity instead. This is direct evidence that quiescent galaxies can accrete cold gas after their quenching while keeping their SF subdued. Follow-up observations with JWST and the Atacama Large Millimeter/submillimeter Array will be needed to constraint the nature of the inflowing gas.

JWST PRIMER: a deep JWST study of all ALMA-detected galaxies in PRIMER COSMOS ─ dust-obscured star formation history back to z ≃ 7

First Author: Liu, Feng-Yuan
Instruments: VIRCAM
ProgramIDs: 198.A-2003, 179.A-2005
BibCode: 2026MNRAS.545f1961L

We use deep NIRCam and MIRI imaging from the James Webb Space Telescope (JWST) PRIMER survey to study the properties of ALMA-detected (sub)mm sources in the COSMOS field, with the aim of defining the cosmic history of dust-enshrouded star formation. The wealth of ALMA data in this field enabled us to isolate a robust sample of 128 (sub)mm sources within the 175 arcmin

$^2$

PRIMER COSMOS survey footprint, spanning two decades in (sub)mm flux density. The JWST imaging is deep and red enough to reveal secure galaxy counterparts for all of these sources. This 100 per cent identification completeness is accompanied by a high level of redshift completeness: 52 per cent of the sources have spectroscopic redshifts, and this has enabled us to refine the photometric redshifts for the remaining galaxies. Armed with robust redshift information, we calculate the star formation rates (SFRs) and stellar masses (

$M_*$

) of all 128 ALMA-detected galaxies, and place them in the context of other galaxies in the field. We find that the vast majority of star formation is dust-enshrouded in all of the ALMA-detected galaxies, with SFR ranging from

$\simeq 1000\, {\rm {\rm M}_{\odot }\, yr^{-1}}$

down to

$\simeq 20\, {\rm {\rm M}_{\odot }\, yr^{-1}}$

. We also find that virtually all (126/128) have high stellar masses,

$M_* > 10^{10}\, {\rm {\rm M}_{\odot }}$

, independent of redshift. The unusually high quality of our sample enables us to make a robust estimate of the contribution of the ALMA-detected galaxies to cosmic SFR density,

$\rho _{\rm SFR}$

. The existing ALMA imaging only covers

$< 20$

per cent of the PRIMER COSMOS area, but based on our knowledge of all other massive galaxies in the field, we produce a completeness-corrected estimate of dust-enshrouded

$\rho _{\rm SFR}$

. This confirms that ultraviolet-visible star formation dominates

$\rho _{\rm SFR}$

$z > 4$

, but also indicates that dust-enshrouded star formation still makes a contribution of

$\simeq 20$

per cent at

$z \simeq 8$

, and

$\simeq 5$

per cent at

$z \simeq 10$

Molecular Gas Morphological Analogs for the Milky Way

First Author: Evans, Neal J., II
Instruments: ALMA_Band_6
ProgramIDs: 2013.1.00803.S, 2013.1.01161.S, 2015.1.00121.S, 2015.1.00782.S, 2015.1.00925.S, 2016.1.00386.S, 2017.1.00392.S, 2017.1.00766.S, 2017.1.00886.L, 2018.1.01651.S, 2018.A.00062.S, 2015.1.00956.S, 2018.1.01321.S
BibCode: 2026ApJ...998L..23E

Complete catalogs of molecular clouds in the Milky Way allow analysis of the molecular medium and the star formation properties of the Milky Way that closely follows the method used for nearby galaxies. We explore whether the big dip in the radial distribution of molecular gas in the Milky Way is peculiar and find several other galaxies with similar patterns, all with similar morphological classifications of YClxxGnR, indicating a clearly defined, long bar leading to a grand-design spiral. This category is fairly rare among galaxies in the PHANGS sample, but all galaxies with this classification have some evidence for dips in the radial distribution of CO emission. The lengths of the bars correlate with the extents of the dips. The Milky Way and the other galaxies with dips have similar stellar masses and star formation rates, both lying near the high ends of the distributions for all PHANGS galaxies.

Polarimetry and albedo of the near-Earth asteroid 2025 FA22

First Author: Rivet, J.-P.
Instruments: FORS2
ProgramIDs: 115.29F0, 092.C-0639, 095.C-0925
BibCode: 2026A&A...710A.358R

We report spectropolarimetric and broadband polarimetric observations of the near-Earth asteroid (NEA) 2025 FA22 during its close approach on 18 September 2025 (about two Moon distances). With a diameter estimated between 130 and 290 m, 2025 FA22 is among the largest NEAs observable at such proximity, prompting an International Asteroid Warning Network (IAWN) rapid-response campaign. Although early orbital solutions indicated a possible impact in 2089, further follow-up astrometric observations ruled out a collision hazard. The favourable geometry of this close encounter enabled dense coverage of the positive part of the phase-polarisation curve, from the high polarisation domain (high phase angles), to near the inversion angle where the linear polarisation fraction vanishes. The spectropolarimetric observations provided the wavelength dependence of the polarisation fraction. Using empirical relationships, an estimate of the geometric albedo could be drawn from the slope of the phase-polarisation curve at an inversion angle p_v = 0.17 ± 0.04 in the V band. This value, together with the spectropolarimetric trend, provides constraints on the taxonomic class, with the results being most consistent with an M (or Xc)-type classification. These results demonstrate the value of polarimetry and spectropolarimetry for the rapid characterisation of newly discovered NEAs in planetary defence campaigns.

RX Gru: A short-period pre-main-sequence eclipsing binary with a distant circumbinary companion

First Author: Marcadon, F.
Instruments: FEROS, HARPS
ProgramIDs: 60.A-9122, 60.A-9036, 077.D-0085, 087.C-0012, 089.C-0415
BibCode: 2026A&A...710A.394M

We report the discovery of a new short-period pre-main-sequence eclipsing binary, RX Gru, orbited by a distant circumbinary companion. We characterised the system by analysing the photometric observations from the Solaris network, the Transiting Exoplanet Survey Satellite, and the Super Wide Angle Search for Planets survey, combined with the radial velocities from four high-resolution spectrographs: HARPS, FEROS, CHIRON, and HRS. We derived the parameters of the eclipsing components, which are M_Aa = 1.004_−0.026^+0.027 M Aa = 1 . 004 − 0.026 + 0.027 M_⊙, R_Aa = 1.007 ± 0.021 R_⊙, and T_{eff, Aa} = 5379 ± 289 K for the primary and M_Ab = 0.985_−0.024^+0.025 M Ab = 0 . 985 − 0.025 + 0.024 M_⊙, R_Ab = 1.024 ± 0.023 R_⊙, and T_{eff, Ab} = 5322 ± 278 K for the secondary. We determined the age of the system from the observed parameters using two evolution codes, MESA and Cesam2k20. We obtained an age of ∼28 Myr, placing the two stars at the very end of the pre-main-sequence phase. We also derived the minimum mass and orbital period of the tertiary companion, which are found to be M_B = 89.0 ± 3.5 M_Jup and P_AB = 2.379_−0.025^+0.10 P AB = 23 . 79 − 0.25 + 0.10 yr, respectively. We conclude that RX Gru consists of a tight inner binary composed of two twin components and an outer low-mass companion (a massive brown dwarf or a very low mass star) in a relatively wide orbit, and we suggest that the system was formed via the dynamical unfolding mechanism coupled with the shared accretion of the circumbinary material by the binary components.

An X-ray and optical spectral study of the changing-look narrow-line Seyfert 1 2MASX J0413-0050

First Author: Vietri, A.
Instruments: EFOSC2, FORS2
ProgramIDs: 106.21HS, 113.26X0, 0104.B-0587
BibCode: 2026A&A...710A.413V

Active galactic nuclei (AGN) showing dramatic spectral and flux variations, either due to changes in the accretion rate ('changing-state' CS-AGN) of the supermassive black hole or in the line-of-sight column density ('changing-obscuration' CO-AGN), have been classified as changing-look AGN (CL-AGN). Here we present a peculiar source, 2MASX J0413-0050, first identified as a narrow-line Seyfert 1 (NLS1s) galaxy in 2004. When re-observed twice in 2021, it showed a transition in the spectral type (towards a Seyfert 1.9) and the complete and mysterious disappearance of the Hβ line while the source was in a high-accretion state. In the meantime, the X-ray flux decreased between observations taken in 2020 and 2022, and again in the most recent spectrum of 2023. Shortly after this, another optical spectrum revealed the re-emergence of both the narrow and broad Hβ components (Seyfert 1.8). Despite the fact that it was not possible to retrieve the line-of-sight column density from the X-ray spectra, which would have helped in assessing whether this event could be attributed to a CO-AGN scenario, the observational evidence does not necessarily support such an interpretation. J0413-0050 may have undergone several switch-on and switch-off phases over the past 20 years, on an unknown timescale, which could have affected the accretion power and, consequently, the optical continuum and so the emission lines coming from the broad-line region (BLR). For these reasons, it is reasonable to classify this source as a CS-AGN. The case of J0413-0050 supports the hypothesis that NLS1s can indeed experience CL phenomena.

Long-term investigation of γ Cas analogs

First Author: Nazé, Yaël
Instruments: ESPRESSO, UVES, XSHOOTER
ProgramIDs: 113.26B9, 71.C-0367, 085.C-0799, 090.D-0212, 194.C-0833, 0102.C-0699, 109.22V6, 105.204D, 113.26KE
BibCode: 2026A&A...710A.410N

Context. The subcategory of γ Cas analogs gathers Be stars with bright and hard X-ray emission. Aims. This paper aims to enlarge the sample of γ Cas analogs studied on long timescales. Long-term variations are expected in such objects for two reasons. First, their Be disk builds and dissipates, leading to changes in optical emission lines, broad-band photometry and possibly even in the X-ray spectrum. Second, such stars are suspected long-period binaries hence velocity variations can be expected, helping to characterize the companions. Methods. Seven targets are analysed in this paper: five of them benefit from a spectroscopic monitoring in the visible (ESO, TIGRE, and amateur data) and three of them have been repeatedly observed at X-ray wavelengths (using XMM-Newton, Chandra, and Swift). Broad-band photometric data, sampling both long and short timescales, are also examined in support of the optical and X-ray spectroscopy. Results. We confirm the binary status of five targets (HD 44458, HD 110432, HD 119682, HD 161103, and HD 162718) and propose first orbital solutions for all of them (they remain preliminary for two cases). Their long periods (59─322 d) and small velocity amplitudes (K ∼ 5 km s⁻¹) imply low-mass (∼1 M_⊙) companions. With such properties, these systems appear similar to other Be binaries in general and γ Cas analogs in particular. They also agree with expectations from binary interaction models. In parallel, variations of the X-ray flux are detected in all three targets with a large dataset of X-ray observations. For NGC 6649 9 and HD 162718, these changes are modest (a factor of three) and uncorrelated to simultaneous optical broad-band photometry (which remains rather stable). In contrast, SS 397 varies by nearly one dex and the largest and best monitored X-ray changes correlate well with optical variations. At minimum flux, SS 397 keeps a hard X-ray spectrum despite a nearly normal L_X/L_BOL ratio, which has not been seen yet among γ Cas analogs. Finally, the photometric behaviours on short timescales of HD 161103, SS 397, and NGC 6649 9 appear linked to broad frequency groups, as typically found for Be stars (including γ Cas analogs). The frequency spectrum of HD 162718 displays a complex mix of (isolated) periodicities with the main one at 6.658 d⁻¹. This target is thus one of the rare γ Cas analogs to display a strong high-frequency signal typical of β Cep activity.

The high-altitude, inner-disc, and chemically peculiar open cluster UBC 1052

First Author: Donada, Judit
Instruments: FLAMES, GIRAFFE, UVES
ProgramIDs: 082.D-0726, 111.255H, 079.C-0131
BibCode: 2026A&A...710A.381D

Context. Of the thousands of newly discovered open clusters (OCs) thanks to the exquisite precision of the Gaia mission data, only a small fraction has been observed with high-resolution spectroscopy. Particularly, the population of OCs in the inner disc at relatively high altitudes (Z) from the Galactic plane remains poorly studied. Few such high-|Z| inner-disc OCs have been detected, and most are sparse groupings of stars that still await confirmation as real OCs. Aims. We performed a detailed spectroscopic analysis of the high-|Z| inner-disc OC UBC 1052, an old cluster located at a cylindrical Galactocentric radius R_GC = 6.1 kpc, where it is one of a few OCs situated at a considerable altitude (Z = 340 pc). Methods. We used FLAMES/VLT to acquire high signal-to-noise ratio UVES spectra of four red clump (RC) members (G ∼ 14 mag), from which we derived high-precision radial velocities and local thermodynamic equilibrium chemical abundances for 23 elements. A strict line-by-line differential analysis was carried out using a reference RC star and a solar analogue in the OC M 67, allowing us to derive very precise abundances for each star (a median precision in [X/H] of ≃0.06 dex). We also acquired GIRAFFE spectra for other candidate member stars and derived their radial velocities. Results. We determine that UBC 1052 has an age of 2.25 ± 0.25 Gyr, a distance of 3.11 ± 0.07 kpc, an extinction of A_V = 1.23 mag, and a mean radial velocity of v. We find that the four RC stars have fully compatible chemical abundances, thus confirming UBC 1052 as a real OC. It has [Fe/H] = +0.05 ± 0.01 dex, and with [X/H] dispersions among the four stars <0.03 dex for 20 elements, we give conservative limits for chemical inhomogeneities at ≃0.05 dex for these species. Conclusions. UBC 1052 stands out as the oldest and highest-|Z| inner-disc OC studied at high resolution to date, being located in the poorly sampled inner Galactic region where old OCs and OCs with large maximum excursions from the plane are scarce. Its relatively low [Fe/H] at its R_GC suggests it is a rare candidate for an inward-migrated OC in the inner disc. Its detailed abundance pattern (e.g. [Ba/Zr] and [Nd/Y]) shows some interesting features that appear to be unique in the current census of OCs studied at high resolution, making it an interesting object for potential strong chemical-tagging searches for already dispersed member stars.

A large, chemically enriched, neutral gas reservoir in a galaxy at z = 6.782

First Author: Saccardi, A.
Instruments: XSHOOTER
ProgramIDs: 110.24CF
BibCode: 2026A&A...710A.363S

The physical and chemical characterization of galaxies formed within the first billion years after the Big Bang remains one of the central goals in contemporary astrophysics. For the last two decades, optical and near-infrared spectroscopy of long gamma-ray bursts (GRBs) have been heralded as an effective diagnostic to probe the interstellar medium (ISM) of the galaxies hosting these events and their metal and dust content, reaching even the most distant redshifts. An opportunity to fulfill this expectation was provided by the recent blast triggered by the Neil Gehrels Swift Observatory of GRB 240218A at redshift z = 6.782. From the GRB explosion, we were able to study a high-redshift galaxy selected in a complementary way with respect to flux-limited surveys, not depending on galaxy luminosity and stellar mass. Furthermore, the GRB afterglow allowed us to perform a coring of the galaxy ISM and to determine its kinematic and chemical properties. We present the VLT/X-shooter spectrum of its afterglow enabling the detection and the detailed characterization of neutral-hydrogen, low-ionization, high-ionization and fine-structure absorption lines, as well as excited level transitions. From this rich variety of absorption lines associated with gas inside and around the GRB host galaxy, we determined the metallicity, kinematics, chemical abundance pattern and dust depletion. This provides the first detailed characterization of the neutral gas of a galaxy at z > 6.5. Thanks to the presence of fine-structure absorption lines, we were able to estimate the distance of the closest absorbing gas clouds as d_II = 620₋₁₄₀⁺²³⁰ d II = 620 − 140 + 230 pc. We determine a high neutral hydrogen column density, log(N(H I)/cm⁻²) = 22.5 ± 0.3, which is the highest one at z ≳ 6 determined so far for a GRB host galaxy, as well as a surprisingly high metal column density, log(N(Zn II)/cm⁻²)≥14.3. The observed metallicity of the host galaxy system is [Zn/H] ≥ −0.8, with a dust depletion level of [Zn/Fe] > 0.4. The high hydrogen column density, metal abundances, and dust depletion in the neutral gas align with those of the ionized gas of very high-redshift galaxies unveiled by ALMA and JWST, testifying that a rapid build-up of metals and dust, and massive neutral hydrogen reservoirs seem to be common features of galaxies in the early Universe. This research highlights the remarkable potential of GRBs as tools to investigate the detailed properties of galaxies deep into the re-ionization epoch, and stresses the importance of new missions capable of enlarging the sample of very high-redshift GRBs.

51 Peg b revisited with VLT/CRIRES⁺: Constraints on atmospheric thermal structure, chemical composition, and an alternative orbital solution

First Author: Cont, D.
Instruments: CRIRES
ProgramIDs: 114.279X
BibCode: 2026A&A...710A.345C

So far, the majority of high-resolution spectroscopy studies on exoplanet atmospheres have focused on transiting planetary systems. Consequently, the atmospheres of non-transiting exoplanets remain poorly explored, and the potential of high-resolution spectroscopy for determining key planetary parameters beyond their atmospheric properties has not been fully exploited. We obtained high-resolution emission spectra of the non-transiting hot Jupiter 51 Peg b in the K band with VLT/CRIRES⁺ to study its atmospheric thermochemical and dynamical structure and derive additional planetary parameters from the Doppler shift of its spectral lines. Using the cross-correlation technique, we confirmed the spectral signature of H₂O in the planetary emission spectrum and a non-inverted atmospheric temperature profile. An indication was also found for the presence of atmospheric CO, although with a signal strength below the threshold for significant detection. The atmospheric chemical and thermal conditions were quantitatively constrained by use of a Bayesian retrieval framework, which yielded a high metallicity value (2.63_+0.93^−1.00 dex) suggestive of chemical quenching, a solar C/O ratio (0.54_−0.23^+0.18), and a temperature profile in the upper atmosphere in line with the expected planetary equilibrium temperature. Moreover, we measured an excess of spectral line broadening, which suggests the presence of atmospheric dynamics in the atmosphere of 51 Peg b. The planetary signal was recovered at an orbital semi-amplitude of 102.8_−9.1^+8.3 km s⁻¹, differing from previous high-resolution measurements. From the obtained orbital semi-amplitude, we further derived the surface gravity (3.15 ± 0.12 log cgs), mass (0.61_−0.05^+0.06 M_Jup), and orbital inclination (49.8_−5.7^+5.8 deg) of 51 Peg b. The mass and inclination values differ from those reported in earlier works. Overall, this study provides new constraints on the thermochemical and dynamical properties of 51 Peg b's atmosphere and demonstrates the potential of high-resolution emission spectroscopy for measuring parameters related to the planetary orbital motion.

With arms wide open: A VLT/MUSE view of the mechanisms driving unwinding spiral arms in cluster galaxies

First Author: Lassen, Augusto E.
Instruments: MUSE
ProgramIDs: 109.23DA
BibCode: 2026A&A...710A.215L

Context. The environmental mechanisms driving unwinding spiral arms in cluster galaxies remain debated. While earlier studies attributed this phenomenon primarily to gravitational interactions, more recent works suggest that ram-pressure stripping (RPS) alone can induce unwinding arms. Aims. Using VLT/MUSE observations, we present a spatially resolved investigation of the external mechanisms responsible for spiral-arm unwinding. We focused on two galaxies, UG101 and UG103, selected from a larger sample of unwinding systems. They are selected as tidal- and RPS-driven candidates, respectively, based on the presence or absence of close neighbors. Methods. We estimated the galactocentric radius at which tidal forces, either from a companion or the cluster potential, become relevant (R_tid). We examined gas and stellar kinematics, exploiting how these two components respond differently to gravitational and hydrodynamical perturbations. The spectrophotometric code SINOPSIS was used to map stellar populations in different age bins and constrain the unwinding timescale for each galaxy. Results. For UG101, we find R_tid ≍ 1.5 R_e, while the unwound features extend beyond this radius. Additionally, UG101 shows irregular stellar and gas kinematics; its rotation curve indicates similar stellar and gas motions, although the gas appears truncated on one side and extended on the other. For UG103, neither the closest companion (r_proj ∼ 117 kpc) nor the cluster appears capable of triggering the unwinding arms through tidal forces. UG103 displays regular stellar kinematics but disturbed gas kinematics, with a truncation on the disk side that likely faces the intracluster medium wind and gas extended in the opposite direction. Stellar population maps show the emergence and subsequent unwinding of the spiral arms in UG103 on timescales consistent with its inferred cluster infall time (∼1.6 Gyr). Conclusions. We conclude that spiral-arm unwinding in UG101 and UG103 is primarily driven by tidal interactions and RPS, respectively, although a combined effect cannot be excluded in the case of UG101. Our methodology provides a robust framework to disentangle the mechanisms driving spiral-arm unwinding in cluster galaxies from their spatially resolved properties.

MXDFz4.4: A LyC Emitter 250 Myr after the Epoch of Reionization and a First Test of Lyα Morphology as a Tracer of LyC Escape at High Redshift

First Author: Goovaerts, Ilias
Instruments: MUSE
ProgramIDs: 1101.A-0127
BibCode: 2026ApJ..1005...34G

Assessing the contribution of ionizing sources to cosmic reionization is a central goal of extragalactic astrophysics. Understanding and quantifying ionizing escape remains challenging near the Epoch of Reionization. We present the highest-redshift Lyman continuum (LyC) emitter detected to date, MXDFz4.4, at z = 4.442 in the MUSE eXtremely Deep Field, observed only ∼0.25 Gyr after the end of reionization. A high-confidence Lyα line confirms the redshift. LyC flux is detected at 5.3σ in the F435W filter with a flux of 4.2 ± 0.8 nJy, corresponding to a flux measurement at 5.2σ. After correcting for the intrinsic production of LyC photons and the intergalactic medium opacity at z = 4.44, we derive high escape fractions, f_esc, ranging from 50% to 100%. We apply established low-redshift tracers of LyC escape and, for the first time at this redshift, promising Lyα morphological tracers such as the halo fraction (HF). Spectral energy distribution fitting indicates the presence of a recent burst of star formation; we explore its impact on the production and escape of ionizing photons. Lyα-based tracers of f_esc reveal a complex scenario in which the recent burst strongly influences LyC production and escape, combined with a more evolved stellar population. This interpretation is supported by UV diagnostics, including Σ_SFR and sSFR. Our results provide cautious support for the Lyα HF as a LyC escape tracer at high redshift. Considering the burst-driven enhancement in ionizing photon production and escape, we conclude that stochastic star formation in the early Universe likely plays a significant role in the contribution of galaxies to cosmic reionization.

A changing-look Seyfert discovered by eROSITA reveals a two-component broad-line region

First Author: Markowitz, Alex
Instruments: FORS2
ProgramIDs: 109.22XH, 109.23MH, 105.20UT
BibCode: 2026A&A...710A.222M

Context. Extreme sudden changes in the flow of accreting gas onto supermassive black holes manifest themselves via large-amplitude multiband continuum variability, as well as changes to broad Balmer emission profiles, driving changing-look active galactic nuclei (AGN). Aims. X-ray flux monitoring with Spectrum Roentgen Gamma (SRG)/eROSITA revealed that in the Seyfert AGN HE 1237−2252 the soft X-ray flux dipped abruptly, by a factor of 17 within 18 months. We initiated a follow-up campaign that caught the luminosity recovery after the dip, and enabled us to study how the various accretion components, including the broad-line region (BLR) and X-ray-emitting coronae, responded during this flux recovery. Methods. Our campaign included multiband photometry, X-ray spectroscopy, and optical spectroscopy. We tracked as the accretion rate relative to Eddington increased by a factor of 7 in 3 years. Results. Based on broad Hβ variability, HE 1237−2252 was subtype 1.0─1.2 in 2002, transitioned to subtype 1.8 by the time of the luminosity dip, and then transitioned back to subtype 1.0 within 3 months as luminosity recovered. Both transitions saw broad Hβ integrated line flux change by factors of 4─6. The broad Balmer profile is decomposed into a broad Gaussian consistent with virialized gas at 27 ± 3 lt-dy, plus a double-peaked profile, consistent with a diskline structure at ≳5 lt-dy. The diskline component's relative contribution to the total profile increases as continuum flux rises. Conclusions. The lack of significant obscuration in the X-ray spectra, as well as the IR continuum dip, point to an intrinsic pause in the accretion rate as opposed to variable line-of-sight obscuration. Candidates for the underlying mechanisms include propagating cold and warm fronts in the accretion disk. The increased prominence of the diskline BLR component's emission could be due to evolution in the physical extent of the X-ray corona, and in the fraction of > 13.6 eV photons intercepted by the diskline, as the accretion rate increases.

Wide B-type hot subdwarf binaries: I. Orbital and atmospheric parameters

First Author: Molina, Francisco
Instruments: UVES
ProgramIDs: 113.26RL, 114.274R, 115.287Y, 116.28ZZ, 106.2105, 098.D-0018, 099.D-0014, 096.D-0180, 097.D-0110, 093.D-0629, 088.D-0364, 0100.D-0082, 0101.D-0200, 0102.D-0255, 0103.D-0129, 0104.D-0135, 105.20L2
BibCode: 2026A&A...710A.280M

Context. Long-period binary systems containing a B-type hot subdwarf (sdB) and a main sequence (MS) companion are thought to originate from binary interactions involving stable mass transfer from the red giant, which is the progenitor of the sdB, to the MS companion. However, despite the recent progress in modelling their population, some of their observed properties are not fully understood. Because the determination of their orbits requires extended campaigns of high-resolution spectroscopic observations, there have only been a limited number of long-period sdB binaries with completely determined orbital parameters studied thus far. Aims. We aim to expand the current sample of long-period sdB binaries with fully determined orbital parameters through the analysis of high-resolution spectroscopic data. In addition, we analyse the atmospheric parameters of the cool companions. Increasing the number of well-characterised systems will provide valuable insights into their formation channels and main characteristics. Methods. A sample of 32 wide binary systems containing sdB stars was selected for the analysis of the radial velocity (RV) curves of both companions. The dataset consisted of high-resolution spectra obtained with the HERMES and UVES spectrographs. The orbital parameters were derived by simultaneously fitting Keplerian orbits to the RVs of the sdB and its companion. The atmospheric parameters of the cool companions were determined using the GSSP code, which analyses the master spectra of the systems with a grid of local thermal equilibrium (LTE) atmospheric models. An additional sample of wide sdB binaries was built by cross-matching the Gaia NSS catalogue with literature catalogues of sdB candidates and spectroscopically confirmed sdB systems. The outcomes from both samples were compared with existing theoretical models to assess their consistency with current formation and evolutionary scenarios. Results. We obtained complete orbital solutions for 32 wide sdB binaries. The orbital period distribution of the ground-based spectroscopic sample is in reasonable agreement with population-synthesis predictions, except for two outliers. The CMD further suggests that current models overpredict systems with the coolest companions, since the observed systems with BP − RP > 0.3 are associated with companions hotter than 6000 K. The observed period-mass ratio distribution is consistent with recent population synthesis predictions and suggests that the unexplained second branch found in these models is mainly populated by old systems. Setting aside the two long-period outliers, we find the data do not support a clear increase in eccentricity with orbital period, whereas the Gaia-based candidate sample displays a discrepant behaviour, owing to selection effects and larger uncertainties.

A decade of monitoring the HIP 41378 planetary system: Masses and orbital periods of six planets and a planet candidate

First Author: Grouffal, S.
Instruments: ESPRESSO, HARPS
ProgramIDs: 198.C-0169, 105.20G0, 0102.C-0171
BibCode: 2026A&A...710A.275G

Multi-planetary systems provide key constraints on planet formation and evolution, as their architecture encodes the dynamical history of planets formed within a common protoplanetary disc. However, the current population remains strongly biased towards compact, short-period systems, and only a limited number of such systems with measured masses and radii are known. HIP 41378 is an exceptional system hosting five transiting planets with orbital periods of up to 1.5 years, including an ultra-low-density planet, HIP 41378 f. The outer transiting planets d and e remained poorly constrained with unknown periods and masses, leaving the system architecture only partially characterised. We present long-term monitoring of this target with high-precision radial-velocity (RV) instruments (HARPS, HARPS-N, HIRES, and ESPRESSO) and space-based photometry spanning 2015─2024. We detected RV signals for all the planets, confirming their orbital periods and constraining their masses. In particular, the RV data strongly favour an orbital period of P_d = 278 days for planet d and refine the orbital period of planet e to P_e = 393₋₅⁺³ days. We measured a new mass of M_f = 25 ± 5 M_⊕ for HIP 41378 f, confirming its super-puff nature with a bulk density of ρ_f = 0.166_−0.036^+0.033 g cm⁻³. We also confirm the planetary nature of HIP 41378 g, a non-transiting planet with a 63-day period, and determine its minimum mass. In addition, the RVs reveal a long-period signal, with P = 2602₋₄₃₃⁺⁴⁶⁸ days, which we attribute to the candidate planet HIP 41378 h, although a stellar magnetic cycle cannot be excluded. Finally, we investigated the system's dynamical architecture and resonant structure, assessed its completeness by constraining additional undetected planets, and looked into the implications for the origin and internal structure of the remarkable planet HIP 41378 f.

Destructuring the disk of AB Aurigae: Dynamics and accretion

First Author: Boccaletti, Anthony
Instruments: SPHERE
ProgramIDs: 108.227A, 0104.C-0157, 112.25CD
BibCode: 2026A&A...710A.263B

Context. The young disk around AB Aur features a complex assembly of spiral arms, several compact structures, and a protoplanet candidate, AB Aur b, suggesting ongoing planet formation in this young system. Because of its brightness and spatial extent, AB Aur represents a perfect laboratory for investigating the conditions under which planets start to form around intermediate-mass stars. Aims. In this paper, we present near-IR polarized images of the AB Aur disk at three epochs spanning 3.85 years with SPHERE/IRDIS, as well as Hα images obtained with SPHERE/ZIMPOL at a single epoch. The purpose of this study is to analyze the dynamics of the entire disk and of the various structures in near-IR polarimetry, and to identify sources of Hα emission to derive constraints on their mass accretion rate. Methods. We developed a method to measure the rotation of the disk as a function of the radius, covering physical separations from as close as ~25 au up to 400 au. We applied this method to the global structure of the disk as well as to specific features of interest, including both extended or compact sources. For the compact sources, we performed orbital analyses. We also studied the variability of shadows seen as thin radial streaks. For the Hα data, we extracted photometric measurements of several features and derived estimations of the accretion luminosities and mass accretion rates, assuming three different accretion models. Results. The dynamical study in the near-IR shows that the disk globally follows Keplerian rotation, but we observe a departure from this behavior at radii smaller than ~60 au. At the smallest radius of ~25 au, we measure a deviation from Keplerian rotation as large as ~12° over 3.85 years, demonstrating sub-Keplerian rotation. The two bright spirals within the millimeter cavity have different dynamic trends, and we discuss their possible link with the identified planet candidates. We also discuss the implications of the non-Keplerian behavior, and we posit that it could be related to interactions with multiple protoplanets orbiting out of the disk plane on elliptical orbits. Furthermore, the orbital analysis of the compact sources (labeled f1, f2, and f3) suggests that their orbital planes are significantly inclined with respect to the disk plane by several tens of degrees. The variability of the shadows suggests that they are produced by optically thick regions located within ~60 au. For the photometric analysis in Hα, we derive a flux of about 8.22 × 10⁻¹⁵ erg/s/cm² for the entire feature f1, but only 6.46 × 10⁻¹⁶ erg/s/cm² at the location of AB Aur b, consistent with non-detection. If f1 were a point source and the accretion remained constant for 1 Myr, it would correspond to ~5-20 Jupiter masses according to the magnetospheric accretion model or ~6-10 Jupiter masses according to the boundary layer accretion model. We further discuss the non-detection of Hα emission on AB Aur b. Finally, we discuss the binarity of the host star, in particular using Gaia measurements. Conclusions. AB Aur is a rare system in which the morphology and dynamics can be studied at a very high level of detail, contrasting with the generic picture of a young planet-forming disk. The excellent image quality of SPHERE, both in the near-IR and in the visible, allows us to track the disk rotation with unprecedented precision thanks to the stability of the instrument across several years and to study localized Hα emissions in the disk. Overall, these observations strongly argue for an active and complex phase of planet formation in this system.

Ariel stellar characterisation: IV. Fundamental parameters of 18 hot stars in the Ariel mission candidate sample

First Author: Ramler, H.
Instruments: ESPRESSO, HARPS
ProgramIDs: 112.25UT, 108.22LR, 109.22Z4, 108.22GS, 0103.C-0889, 0104.C-0605
BibCode: 2026A&A...710A.297R

Context. The characterisation of exoplanetary systems depends on the accurate determination of host star parameters. The Ariel mission will probe the atmospheres of a statistically significant sample of exoplanets, and so requires a precise characterisation of the stellar properties well before its launch in 2031. The homogeneous determination of stellar parameters for Ariel will enable both the optimisation of the final target list and set roots for a reliable interpretation of the formation and evolution of planetary systems. Such a homogeneous characterisation has thus far only been carried out for the cool (T_eff ≲ 7000 K) host stars among the Ariel target candidates. Aims. We present a uniform determination of fundamental stellar parameters for 18 hot stars (T_eff ≳ 7000 K) in the Tier 1 candidate list of the Ariel mission candidate sample. Methods. We adopted an iterative spectro-trigonometric approach optimised for high-temperature stars (T_eff ≳ 7000 K). Highresolution spectra were analysed using the ZEEMAN code with χ² minimisation, combining model fits to metal and Balmer lines. Surface gravity was refined using photometry-based radii and masses from stellar evolutionary tracks. Results. We derived effective temperatures, surface gravities, projected rotational velocities, microturbulent velocities, overall metal-licities, iron abundances, stellar masses, and radii for our sample of 18 hot stars. Our results were validated against a set of benchmark stars previously presented in the literature, confirming that our methods yield results consistent with previous studies. This ensures an internally consistent parameter scale and maintains continuity across the transition from cool to hot stars within the Ariel sample. Conclusions. The derived parameters provide an internally consistent basis for studying the link between stellar properties and planetary characteristics in intermediate-mass stars (1.5 < M < 2.32 M_⊙). Building on our previous work on FGK host stars, we show that correlations between stellar mass, metallicity, and planetary radii also extend to early-type stars, and stellar properties influence the architecture of multi-planet systems.

LCEz4-M1: A Lyman Continuum Emitter Candidate at z = 4.444 in the MUSE Hubble Ultra Deep Field

First Author: Zhu, Shuairu
Instruments: MUSE
ProgramIDs: 094.A-0289, 095.A-0010, 096.A-0045, 1101.A-0127
BibCode: 2026ApJ..1005L...3Z

High-redshift Lyman continuum emitters (LCEs) are crucial for understanding how galaxies ionize the neutral hydrogen in the epoch of reionization. However, detected LCEs at z > 4 are quite rare. Here, we report an LCE candidate at z = 4.444, dubbed LCEz4-M1, which is one of the highest-redshift LCE candidates currently known. The redshift is determined from the Lyα emission line detected in the Very Large Telescope (VLT)/MUSE spectrum. The Lyman continuum (LyC) signal is detected independently in the Hubble Space Telescope F435W image and the VLT/MUSE spectrum at significances of ≃3.7σ and ≃2.8σ─3.0σ, respectively. The LyC centroid is spatially consistent with the James Webb Space Telescope (JWST)/NIRCam continuum within the astrometric uncertainty. Adopting the maximum intergalactic medium transmission, we infer conservative lower-limit escape fractions of fesc(F435W)=0.82−0.17+0.13 and fesc(MUSE)=0.75−0.28+0.18 . Using the combined JWST and MUSE dataset, we characterize the physical properties and morphology of LCEz4-M1. In our fiducial JWST-only spectral energy distribution fit, the galaxy is compact but has a moderate current galaxy-integrated star formation surface density, Σ_SFR = 0.38 M_⊙ yr⁻¹ kpc⁻², suggesting that it is not an extreme compact starburst under this fiducial interpretation. While we find no clear evidence for an ongoing major merger for LCEz4-M1, the presence of a faint companion ( ∼0.″5 ) detected in the F277W band suggests a potential minor interaction. We also find that LCEz4-M1 may lie in a locally overdense region, although the environmental interpretation remains tentative. Finally, the low star formation ratio, SFR_{10 Myr}/SFR_{100 Myr}, low Lyα equivalent width, and relatively weak rest-frame optical emission lines of LCEz4-M1 may indicate a postburst LyC leaking phase.

Weighing the mass of LHS 3844 b

First Author: Hacker, A.
Instruments: ESPRESSO
ProgramIDs: 0102.C-0496, 0103.C-0849
BibCode: 2026A&A...710A.312H

Context. LHS 3844 b (TOI-136b) is an ultra short-period, Earth-size exoplanet detected by TESS. It is one of the most favourable objects for atmospheric characterisation and study of its surface with the James Webb Space Telescope. However, the dynamical mass of this planet has not yet been measured. Aims. We aim to determine the mass of LHS 3844 b using high-precision radial velocity (RV) measurements and assess the robustness of the inferred signal across different noise and orbital modelling assumptions. Methods. We analyse 25 ESPRESSO RV observations within a fully Bayesian framework. We explore 15 competing RV models that differ in their treatment of correlated stellar variability (through different Gaussian process (GP) kernels) and long-term drifts. Marginal likelihoods are computed for all models and used for Bayesian model comparison and evidence-weighted parameter estimation. Results. The RV planetary signal is robustly detected across all models, and the inferred semi-amplitude remains stable under all tested noise and drift prescriptions. From the evidence-weighted posterior samples we derive a planetary mass of 2.27 ± 0.23 M_⊕ and a bulk density of 5.67 ± 0.65 gcm⁻³, consistent with a predominantly rocky composition. Model comparison favours GP kernels including periodic or quasi-periodic components associated with stellar rotation and disfavours models with additional long-term drifts. Using interior-structure inference, we find that the core mass fraction is comparable to (or slightly smaller than) Earth's and only trace amounts of water are permitted, supporting a dry, terrestrial interior. We also investigate a tentative additional signal near ~6.9 days, but Bayesian model comparison does not provide conclusive support for its planetary interpretation. Conclusions. We report the first dynamical mass measurement of LHS 3844 b, confirming it as a dense, terrestrial ultra-short-period planet. With its exceptionally well-constrained bulk properties and extensive JWST programme, LHS 3844 b remains a benchmark target for studies of the atmospheres and surfaces of rocky exoplanets.

Upper limits on exosatellites around β Pictoris b

First Author: Kenworthy, Matthew A.
Instruments: CRIRES
ProgramIDs: 114.27DX
BibCode: 2026MNRAS.549g1060K

$\beta$

Pictoris b is one of the closest known directly imaged gas giant exoplanets with an orbit that is almost edge-on to our line of sight, making it an ideal target for radial velocity monitoring to search for massive exomoons. We measure the radial velocity of

$\beta$

Pictoris b over several epochs between October 2024 and March 2025 by using the cross-correlation of a template spectrum with absorption lines in the planet's atmosphere, giving a mean precision of 160 m s

$^{-1}$

. The resultant set of radial velocities is analysed with a periodogram to search for candidate radial velocity (RV) signals indicating a massive exomoon. Although we do not detect an exomoon signal in our data, our detection limits for a single moon are 80 Earth masses at

$P=1$

d and 1 Jupiter at

$P=200$

d, comparable to RV exomoon searches around other substellar companions. The RV limit is comparable with the astrometric exomoon limit at a period of 7 d and a mass of 150

$\mathrm{ M}_\oplus$

, where for longer periods the astrometric searches have lower mass limits. With an additional observing season, the upgraded CRyogenic InfraRed Echelle Spectrograph (CRIRES+) can detect a planet/moon mass ratio of

$10^{-3}$

(

$4\,\mathrm{ M}_\oplus$

) with a period of up to one day, and can detect a Neptune-mass moon at hundreds of Jupiter radii.

The Effect of External Photoevaporation on the Disk Fraction in M17

First Author: Millstone, Samuel
Instruments: HAWKI
ProgramIDs: 111.252G
BibCode: 2026ApJ..1005...13M

A major obstacle to improving models of planet formation is understanding how the local environment influences the lifetimes of the disks in which planets form. The spread in observed disk lifetimes is caused by effects both observational (e.g., target selection, survey sensitivity) and physical (e.g., disk destruction by internal and external photoevaporation); however, the degree to which each plays a role remains poorly constrained. Isolating the impact of external photoevaporation on disk lifetimes benefits from the inclusion of low-mass (≲ 0.5 M_⊙) young stellar objects (YSOs), for which this effect is expected to be most significant. In this work, we measure the inner disk fraction from JHK excess in the ∼6000 M_⊙, ∼1 Myr-old star-forming region (SFR) M17. Using the High Acuity Wide-field K-Band Imager (or HAWK-I) on the Very Large Telescope, we perform a deep photometric survey of an ∼ 8'×8' field toward the region. The ∼4 times greater sensitivity and ∼2−3 times higher resolution compared to previous surveys of M17 reveal 10,339 sources. We select cluster members using the Massive Young Star-Forming Complex Study in Infrared and X-ray (or MYStIX) catalog and find a disk fraction of 28% ± 2%—the first X-ray-selected disk fraction measurement in M17 to include low-mass YSOs, and only the second such measurement in any high-mass SFR. After correcting for observational biases, we find no correlation between disk fraction and incident UV flux within M17, likely due to dynamical mixing within the region. However, when compared with other regions of similar age, we find lower disk fractions in regions with stronger UV fields, suggesting that external photoevaporation decreases the average disk lifetime.

Detection of Persistent Helium Absorption in the 91bg-like Type Ia Supernova 2022an

First Author: Chen, Ping
Instruments: EFOSC2, SOFI, XSHOOTER
ProgramIDs: 108.23MS, 108.220C
BibCode: 2026ApJ..1004L..42C

We present optical and near-infrared (NIR) observations of the fast-declining Type Ia supernova (SN Ia) 2022an. The photometric and spectroscopic properties identify it as a standard 91bg-like event; however, our data reveal a relatively narrow absorption feature with a full width at half-maximum (FWHM) of 75 Å near 1.037 μm in the rest frame of the observed spectra that persists from around 30 days to nearly 90 days after maximum light. We attribute this feature to the He I 1.083 μm line with a blueshifted velocity of 1.3 × 10⁴ km s⁻¹ and a FWHM of 2.1 × 10³ km s⁻¹, supported by the detection of multiple optical He I transitions at earlier epochs with a higher velocity of around 1.5 × 10⁴ km s⁻¹. The high velocity of the helium cannot be explained by helium external to the progenitor at the time of explosion, such as stripped surface helium from a companion star. The properties of the helium absorption in the spectra of SN 2022an instead point to unburned material in the outer ejecta, thus providing the most compelling evidence to date for helium-bearing ejecta in a 91bg-like SN Ia. Such helium has been predicted in sub-Chandrasekhar-mass double-detonation explosions involving a surface helium shell. No theoretical calculations of modern helium-shell double detonations have been performed at epochs similar to those observed for SN 2022an to study the effects of helium on their spectra, revealing a gap between observations and theoretical calculations in our understanding of how helium manifests in SNe Ia. Nevertheless, the discovery of persistent helium absorption in SN 2022an demonstrates the diagnostic power of NIR spectroscopy for understanding thermonuclear supernova explosions by probing the abundance and structure of their ejecta.

Dark-matter-deficient Twins: FCC 224 and FCC 240 as Possible Analogs of NGC 1052-DF2 and DF4

First Author: Buzzo, Maria Luisa
Instruments: MUSE
ProgramIDs: 114.27CM
BibCode: 2026ApJ..1005...15B

The recent "bullet-dwarf" model proposes that high-velocity collisions between dwarf galaxies can produce stellar systems with overluminous globular clusters (GCs) and a deficiency of dark matter, as observed in the NGC 1052 group galaxies NGC 1052-DF2 and NGC 1052-DF4. We present a possible analog system in the outskirts of the Fornax cluster: the ultradiffuse galaxy FCC 224 and its close companion FCC 240. Using deep Very Large Telescope/MUSE integral field spectroscopy, we characterize their stellar populations, internal kinematics, and GC systems to test this formation scenario. Both galaxies exhibit low velocity dispersions. Interpreted with a standard mass estimator at the half-light radius, and allowing for the known limitations associated with flattened systems, their inner dynamics are more naturally explained by stars alone than by either cuspy or cored dark matter halos. Both systems host unusually luminous GCs, closely resembling the top-heavy GC luminosity function of the NGC 1052 pair. Moreover, FCC 224 and FCC 240 are coeval with each other, with mass-weighted stellar ages of ∼10 Gyr, and their GC populations share similarly old ages, in agreement with predictions of the formation scenario. Despite these similarities, FCC 224 and FCC 240 form a much tighter system than DF2 and DF4, with a projected separation of 75 kpc (compared to 240 kpc) and a relative velocity of only 16 km s⁻¹ (compared to 358 km s⁻¹). This distinct configuration may suggest a different present-day manifestation of the same general class of galaxies and provides additional observational constraints on models of their formation and evolution.

A distant brown dwarf coplanar to a warm Jupiter and a hot super-Earth

First Author: Jones, Matias I.
Instruments: HARPS, PLATO Spec, SPHERE
ProgramIDs: 112.25S5, 0104.C-0413, 0101.C-0510, 0103.C-0442
BibCode: 2026Natur.654..614J

In transiting planetary systems, in which planetary sizes are accurately determined from transit observations, the presence of transit-timing variations¹ (TTVs), especially when combined with radial velocity (RV) data, provides powerful constraints on masses and orbital eccentricities. Together, these measurements offer crucial insights into system architecture, formation mechanisms and dynamical evolution. We present long-term RV and transit/TTV monitoring of the relatively young star (age approximately 1 Gyr) TOI-201, revealing an exceptional multi-planet system composed of a hot super-Earth (SE) size planet transiting every 5.8 days, a warm Jupiter (WJ) on a 53-day orbit and an eccentric (e = 0.62) low-mass brown dwarf (BD) on an approximately 8-year orbit, with an estimated mass M_BD of about 16 Jupiter masses. The BD is the longest-period transiting substellar object ever characterized by means of RVs and the only one known to be coplanar with inner planets. The architecture of this system suggests that the SE was formed isolated and in the innermost region of the gaseous disk. On the other hand, the orbital configuration of the outer companions suggests a nearly in situ formation of both objects, with the WJ forming in a dense inner disk. Alternatively, the BD might have formed farther out and migrated inward, while increasing its eccentricity owing to interactions with the disk.

The open cluster NGC 2509: Stellar rotation and main sequence turnoff extension from FLAMES spectroscopy

First Author: Boeche, C.
Instruments: FLAMES, GIRAFFE, UVES
ProgramIDs: 112.25DP
BibCode: 2026A&A...710A.285B

NGC 2509 is a distant (≍2.5 kpc) and little-studied open cluster located in the third Galactic quadrant. It is a moderately old cluster, whose age has not yet been precisely determined. The main-sequence stars in NGC 2509 follow a narrow distribution in the colormagnitude diagram, unlike other clusters of similar age. In addition, its chemical composition has never been investigated. To address these issues and characterize the cluster we performed moderate- and high-resolution spectroscopy with FLAMES@VLT of 132 stars, both dwarfs and giants, which represents a significant fraction (≍73%) of likely members. We provide atmospheric stellar parameters and, for the first time, chemical abundances for 21 species with atomic numbers up to 60. In our analysis we followed two different methodologies, both of which will be used for the incoming WEAVE stellar surveys. We find an average radial velocity for NGC 2509 of 58.6±1.3km s⁻¹ and a mild supersolar metallicity ([Fe/H]≍0.1 dex). This value is slightly higher than expected according to its galactocentric distance, but still compatible with the Galactic gradient. From the lithium content of the dwarfs and the isochrone-fitting method we obtain an age for NGC 2509 of 1.26±0.3Gyr. The reddening across the cluster field is negligible (A_V = 0.25 ± 0.02 mag). The cluster peculiar main sequence turnoff is due to a narrow distribution of the rotational velocities peaking at v sin i ≍ 80 km s⁻¹, with little dispersion. The chemical pattern of NGC 2509 follows the Galactic trends shown by other open clusters in the Galactic thin disk.

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Locating the missing large-scale emission in the jet of M87* with short EHT baselines

Improving the diameters of interferometric calibrators with MATISSE

The Identification of Two JWST/NIRCam-dark Starburst Galaxies at z = 6.6 with ALMA

Constraining the magnetic field strength of a flaring radio core in the compact steep spectrum source 3C 138

First result with AMBER+FINITO on the VLTI: the high-precision angular diameter of V3879 Sagittarii

MANGOS ─ II. Five new giant planets orbiting low-mass stars

Bar-driven gas redistribution suppresses star formation in spiral galaxies: Evidence from dust lanes in NGC 3351

A precessing jet from an active galactic nucleus drives gas outflow from a disk galaxy

A Radially Broad Collisional Cascade in the Debris Disk of γ Ophiuchi Observed by JWST

HyGAL: Characterizing the Galactic ISM with observations of hydrides and other small molecules: III. The absorption lines of [O I], CH, and OH

Spectrally and Spatially Resolved (Sub)Millimeter HCN-to-HCO+ Flux Ratios in Nearby Ultraluminous Infrared Galaxies

From gas to stars along the spiral wave: CO, HCN, and star formation variations across the spiral arms in NGC 4321 and M51

The multi-wavelength vertical structure of the archetypal β Pictoris debris disk

FAUST: XXXI. Grain properties and variability of three sources in GSS 30

A New Framework for Multiline Analysis Combined Kernel Principal Component Analysis and Kernel Shapley Additive Explanations: A Case of NGC 1068 ALMA Band 3 Data

Survival of Molecular Complexity under Recent Supernova Feedback: Detection of Hot Cores in RX J1713.7−3946

Charting circumstellar chemistry of carbon-rich asymptotic giant branch stars: III. SiO and SiS abundances

A Redshift-based Red Selection of Dusty Star-forming Galaxies

JWST's First View of the Most Vigorously Star-forming Cloud in the Galactic Center: Sagittarius B2

New 12C/13C and 14N/15N isotopic ratios measurements in HCN in the Jupiter stratosphere revealed by ALMA

The intrinsic dispersion of elemental abundance ratios in nearby metal-poor halo stars

Spectroscopic Characterization of Young Stellar Populations and Their Feedback in NGC 5253

Mapping a Quasar Outflow from Parsec to Kiloparsec Scales: A Combined HST Absorption and VLT Emission Investigation

Blobs and Blurs: A Citizen Science-identified Catalog of Diffuse Galaxies in the Fornax Cluster

Observational signatures and constraints on the intermediate neutron-capture process: The case of the carbon-enhanced metal-poor star TYC 6044−714−1 (RAVE J094921.8-161722)

VENUS: Strong-lensing Model of MACS J1931.8-2635: Revealing the Farthest Multiply Imaged Supernova

Spatially resolved broad-line region in a quasar at z = 4: Dynamical black hole mass and prominent outflow

ALMA Observations of Magnetic Fields in the Massive Star-forming Region IRAS 18360-0537

The ALMA-QUARKS Survey: Investigating Thermal Feedback of Massive Protostars in Hot Molecular Cores

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): Formaldehyde (H2CO) Emission and Its Links to Disk Properties

CO-dark Molecular Gas Traced by HCO+ in the Diffuse Interstellar Medium

Direct Imaging Discovery of Giant Exoplanet β Pictoris d: A Decade-long Game of Hide-and-seek

Under the glare of a luminous quasar, the FIR continuum is still an excellent tracer of the ISM down to the central kiloparsec

Feeding the Dead: Neutral Gas Inflow in a Long-quenched Ancient Massive Galaxy at z ∼ 2.7 Observed with JWST/NIRSpec

JWST PRIMER: a deep JWST study of all ALMA-detected galaxies in PRIMER COSMOS ─ dust-obscured star formation history back to z ≃ 7

Molecular Gas Morphological Analogs for the Milky Way

Polarimetry and albedo of the near-Earth asteroid 2025 FA22

Chemodynamics of Boötes I with S⁵: Revised Velocity Gradient, Dark Matter Density, and Galactic Chemical Evolution Constraints

Spectrally and Spatially Resolved (Sub)Millimeter HCN-to-HCO⁺ Flux Ratios in Nearby Ultraluminous Infrared Galaxies

New ¹²C/¹³C and ¹⁴N/¹⁵N isotopic ratios measurements in HCN in the Jupiter stratosphere revealed by ALMA

The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO): Formaldehyde (H₂CO) Emission and Its Links to Disk Properties

CO-dark Molecular Gas Traced by HCO⁺ in the Diffuse Interstellar Medium

51 Peg b revisited with VLT/CRIRES⁺: Constraints on atmospheric thermal structure, chemical composition, and an alternative orbital solution