Latest ESO telbib papers

A Protoplanet Candidate in the PDS 66 Disk Indicated by Silicon Sulfide Isotopologues

First Author: Yoshida, Tomohiro C.
Instruments: ALMA_Band_4, ALMA_Band_7
ProgramIDs: 2017.1.01687.S, 2023.1.00334.S, 2023.1.00525.S
BibCode: 2026ApJ...999L..22Y

Despite observational progress in planet formation, the stage in which planetesimals grow into planets remains poorly understood. During this phase, protoplanets may develop gaseous envelopes that are warmer than the surrounding disk gas, potentially providing observable signatures through molecules otherwise depleted in cold regions. In this Letter, we report the detection of the silicon sulfide isotopologues ²⁸SiS J = 16−15 and ³⁰SiS J = 18−17 in the protoplanetary disk around PDS 66 (MP Mus) at a significance of ∼5σ−6σ, using the Atacama Large Millimeter/submillimeter Array. These constitute the second and first detections of ²⁸SiS and ³⁰SiS in a protoplanetary disk, respectively. The emission appears as a compact source at r = 60 au in the southwestern region of the disk, unresolved with a ∼0.″5 beam, and shows a velocity consistent with Keplerian rotation, suggesting a protoplanetary origin. By modeling the line fluxes, we constrain the emitting radius to ∼0.5−4 au and estimate a SiS mass of 10²²─10²³ g, corresponding to at least ∼10% of the silicon contained in local dust grains. Because complete sublimation of a substantial fraction of dust grains by local processes is difficult to achieve, this result instead implies an accumulation of silicon from a larger region. We propose that a circumplanetary envelope surrounding a low-mass protoplanet, where pebble accretion and subsequent sublimation of grains may enhance gaseous silicon abundance with respect to observable dust grains around it, can account for the observed characteristics.

A Multiwavelength Study of Comet C/2022 E3 (ZTF): Complementary ALMA and JWST Investigations of Water and Methanol in Cometary Comae

First Author: Foster, K. D.
Instruments: ALMA_Band_6
ProgramIDs: 2022.1.00997.T
BibCode: 2026AJ....171..162F

Long-period comets, which are often considered to be representative of material in the protoplanetary disk that formed the solar system, are ideal to investigate the question of chemical inheritance in astronomy. Determining the chemistry of comets, both individually and as a population, has become of great importance in comparative studies against sources representative of evolutionary precursors to planetary systems. Contemporaneous observations of long-period comet C/2022 E3 (ZTF) were obtained with JWST and the Atacama Large Millimeter/submillimeter Array (ALMA) in early 2023 March. This work focuses on CH₃OH measurements from both ALMA and JWST, as well as H₂O measurements from JWST. Radiative transfer modeling of CH₃OH and H₂O was performed to investigate spatial variations in rotational temperature, column density, and production rates, as well as a comparison of derived values between the two telescopes. Most of the spatial distributions of the modeled values are centrally peaked, and the modeled values from JWST are all within the error bars of the average values from ALMA. C/2022 E3 (ZTF) also displays an enhancement in modeled rotational temperature in the antisunward direction that is shown to be statistically significant. Based on non-LTE radiative transfer modeling, the declining H₂O rotational temperatures as a function of nucleocentric distance observed by JWST can be explained primarily as a result of rotational line cooling. The values derived in this work are in general agreement with single-dish millimeter-wave observations.

Multiband ALMA Polarization Observations of BHB 07-11 Reveal Aligned Dust Grains in Complex Spiral Arm Structures

First Author: Fourkas, Austen
Instruments: ALMA_Band_3, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2013.1.00291.S, 2016.1.01186.S
BibCode: 2026ApJ...999....4F

Polarization-mode observations from the Atacama Large Millimeter/submillimeter Array (ALMA) are powerful tools for studying the dust grain populations in circumstellar disks. Many sources exhibit polarization signatures consistent with aligned dust grains, yet the physical origin of this alignment remains uncertain. One such source is BHB 07-11, a Class I protobinary object in the Pipe Nebula with complex spiral arm structures in its circumbinary disk. While magnetic fields are often invoked to explain grain alignment in the interstellar medium, the contrasting conditions in circumstellar disk environments demand further investigation into grain alignment mechanisms. To determine BHB 07-11's dominant polarization mechanism, we leverage ALMA polarization-mode dust continuum observations in Bands 3 (λ = 3.1 mm), 6 (λ = 1.3 mm), and 7 (λ = 0.87 mm), in combination with high-resolution dust continuum and spectral line observations in Band 6. Observed polarization vectors in each band are consistent with emission from aligned grains and follow the structure of the spiral arms as shown in the high-resolution observations. Given the relationship between the observed polarization vector orientation and the spiral arms, we find that the polarization morphology is most consistent with grains aligned through a relative velocity flow between gas and dust in the spiral arms, as envisioned in the recently developed badminton birdie-like alignment mechanism, rather than alignment with a magnetic field or other known alignment mechanisms.

CARTA—Cube Analysis and Rendering Tool for Astronomy: A Tool for Big Imaging Data

First Author: Wang, Kuo-Song
Instruments: ALMA_Band_6, ALMA_Band_7, ISAAC
ProgramIDs: 67.C-0595, 2011.0.00647.S, 2015.1.00425.S, 2015.1.01538.S, 2016.1.00484.L
BibCode: 2026PASP..138b4506W

Data generated by modern telescopes continues to grow rapidly as a result of these instruments' advanced capabilities, including wide-field imaging with high angular and spectral resolution. The resulting image cubes are often too large for end users to download and analyze on local desktop computers efficiently. Consequently, it is essential to provide visual analytics tools that can access these large data cubes remotely while enabling efficient and responsive local visualization. The Cube Analysis and Rendering Tool for Astronomy (CARTA; https://cartavis.org), presented in this paper, addresses this challenge. CARTA employs a client─server architecture: data processing is handled on the server side, while the client runs in the user's local web browser to render images and analysis results. This design minimizes data transfer, reduces latency, and enables seamless interaction with massive image cubes without the need for remote rendering. The paper outlines CARTA's implementation, including its architecture, deployment modes, interfaces, and codebase. It also provides an overview of its core features and analytics tools for different types of astronomical data. A long-term development plan for advanced features is also discussed.

oMEGACat. VIII. A Subpopulation Census of ω Centauri

First Author: Clontz, C.
Instruments: MUSE
ProgramIDs: 099.D-0019, 098.D-0148, 097.D-0295, 096.D-0175, 095.D-0629, 094.D-0142, 109.23DV, 105.20CR, 0104.D-0257, 0103.D-0204, 0102.D-0270, 0101.D-0268, 0100.D-0161, 105.20CG
BibCode: 2026ApJ...998..177C

An understanding of the assembly history of the complex star cluster Omega Centauri has long been sought after, with many studies separating the stars on the color─magnitude diagram into multiple groupings across small magnitude ranges. Utilizing the oMEGACat combined astro-photometric and spectroscopic data set, we parse 14 subpopulations from the upper red giant branch to below the main-sequence turnoff. We combine our results with previous works to estimate the age and age spread of each population. We find that the chemically enhanced (P2) populations are all ∼1 Gyr younger (∼11.6 Gyr old) and have significantly higher intrinsic age spreads (0.6 Gyr) than the primordial (P1) populations (∼12.6 Gyr old, 0.3 Gyr spread), with the intermediate (Im) populations falling in between the two. Additionally, we connect for the first time the chromosome diagram to the two-stream age─metallicity relation, allowing us to link the P1 and P2 stars to the distinct star formation tracks, proposed to be in situ and ex situ contributions to the cluster's assembly. Our results are consistent with some suggested formation models and rule out others, but no current model can explain all observed features of the subpopulations.

Possible collision-induced outflows and triggered star formation in the molecular complex G34

First Author: Sun, Mingke
Instruments: LABOCA
ProgramIDs: 085.F-9526, 085.F-9505, 082.F-9701, 080.F-9701, 081.C-9501, 079.C-9501, 078.F-9040, 181.C-0885
BibCode: 2026MNRAS.546f2285S

G34 is an active star-forming region with complex velocity components. Within the 38─63 km s

$^{-1}$

velocity range, we identify a possible cloud─cloud collision at a distance of

$\sim$

3 kpc. Using the

$\rm ^{12}CO$

(

${\it J}$

= 1─0) line from the Purple Mountain Observatory 13.7-m millimeter telescope to trace the diffuse gas structures associated with the collision. The gas components at 38─50 and 53─63 km s

$^{-1}$

exhibit a U-shaped complementary distribution and a bridge feature in the position─velocity diagram. At the collision interface, the velocity dispersion of

$\rm ^{12}CO$

is significantly enhanced, which may result from the impact of the collision. We analyse the spatial distributions of 6.7 GHz CH

$_3$

OH masers, APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) clumps, H II regions, young stellar objects, and O-type stars, finding that most are concentrated near the collision interface. This supports a strong coupling between cloud─cloud collisions and star formation. In addition, we detect H I self-absorption features and molecular outflows at the interface. Based on observations of 6 and 2 cm H

$_2$

CO lines from the Effelsberg 100 m and Tianma Radio Telescope 64 m telescopes, along with NH

$_3$

lines from the Nanshan 26 m telescope, we derive an H

$_2$

volume density of

$10^4$

─

$10^5$

$^{-3}$

in the compressed region. Finally, we compare the collision time-scales (

$\gtrsim$

0.35 Myr), the dynamical age of the H II region G34.26+0.15 (

$\gtrsim$

0.33 Myr), and the outflow time-scale (

$\sim$

7.5 Myr). The results suggest that gas at the base of the U-shaped structure was compressed during the collision and driven into the outflow. After millions of years of evolution, the gas density increased, potentially triggering star formation.

Red Noise─based False Alarm Thresholds for Astrophysical Periodograms via Whittle's Approximation to the Likelihood

First Author: Ejaz, Amna
Instruments: HARPS
ProgramIDs: 074.D-0380, 086.C-0230
BibCode: 2026AJ....171..124E

Astronomers who search for periodic signals using Lomb─Scargle periodograms rely on false alarm level (FAL) estimates to identify statistically significant peaks. Although FALs are often calculated from white noise models, many astronomical time series suffer from red noise. Prewhitening is a statistical technique in which a continuum model is subtracted from the log power spectrum estimate, after which the observer can proceed with a white-noise treatment. Here we present a prewhitening-based method of calculating frequency-dependent FALs. We fit power laws and autoregressive models of order 1 to each Lomb─Scargle periodogram by minimizing the Whittle approximation to the negative log-likelihood (NLL), then calculate FALs based on the best-fit model power spectrum. Our technique is a novel extension of the Whittle NLL to datasets with uneven time sampling. We demonstrate FAL calculations using observations of α Cen B, GJ 581, HD 192310, synthetic data from the radial velocity (RV) fitting challenge, and Kepler observations of a differential rotator. The Kepler data analysis shows that only true rotation signals are detected by red noise FALs, while white noise FALs suggest all spurious peaks in the low-frequency range are significant. A high-frequency sinusoid injected into α Cen B logR'HK observations exceeds the 1% red noise FAL despite having only 8.9% of the power of the dominant rotation signal. In a periodogram of HD 192310 RVs, peaks associated with differential rotation and planets are detected against the 5% red noise FAL without iterative model fitting or subtraction. The software for calculating red noise─based FALs is available on GitHub.

Accretion History of AGNs: A Multiwavelength Comparison of X-Ray- and Infrared-selected AGNs

First Author: Kelly, Thresa
Instruments: VIRCAM
ProgramIDs: 179.A-2005
BibCode: 2026ApJ...997..366K

Identifying active galactic nuclei (AGNs) using only one wavelength region may miss AGNs with characteristics unfavorable for the identification method, which introduces bias in the sample. To better understand these selection effects, we compare the multiwavelength properties of 2584 X-ray- and IR-selected AGNs at z < 3 in the COSMOS field. The X-ray-selected sample consists of the 2219 AGNs with intrinsic 0.5─10 keV X-ray luminosity greater than 10⁴³ erg s⁻¹; the 993 IR-selected AGNs are identified by their high-contrast, power-law IR colors using Spitzer/IRAC observations. We find that both selection methods miss a significant fraction of AGNs, as only 24.3% of AGNs (628 out of the total of 2584 AGNs) are recovered by both selection criteria. X-ray selection can capture the most diverse range of multiwavelength spectral emission features, while IRAC selection is biased against AGNs with a steeply decreasing power flux (λF_λ) between 1 and 6 μm. For AGNs with X-ray detections, IRAC-selected sources are 2.5× more X-ray luminous than AGNs not identified by their IR colors. IRAC-selected AGNs without detectable X-rays are obscured, as they have a mean X-ray correction factor log(LX,obs/LX,int)= −1.4; 28.5%─42.2% of these AGNs are Compton-thick (according to estimated column densities). Only 1.4% of X-ray-selected AGNs are Compton-thick. The AGN selection technique used significantly impacts the overall characteristics of the resulting AGN sample.

ELFO: A Python Package for Emission Line Fitting Optimization in Integral Field Spectroscopy Data

First Author: Guo, Hui
Instruments: MUSE
ProgramIDs: 0103.B-0762
BibCode: 2026AJ....171..106G

Integral field spectroscopy (IFS) provides spatially resolved spectra, enabling detailed studies that address the physical and kinematic properties of the interstellar medium. A critical step in analyzing IFS data is the decomposition of emission lines, where different velocity components are often modeled with Gaussian profiles. However, conventional fitting methods that treat each spectrum independently often yield spatial discontinuities in the fitting results. Here, we present Emission Line Fitting Optimization (ELFO), a Python package for IFS spectral fitting. ELFO uses the results of neighboring spectra to determine multiple initial guesses and selects the result that exhibits spatial smoothness. We tested ELFO on IFS data of two quasars obtained from the Multi-Unit Spectroscopic Explorer, where it successfully corrected anomalous fits, revealed previously unresolved substructures, and made large-scale kinematic structures more evident. With minor modifications, this method can also be easily adapted to other IFS data and different emission lines.

Chemical analysis of the Milky Way's nuclear star cluster: Evidence for a metallicity gradient

First Author: Schultheis, M.
Instruments: KMOS
ProgramIDs: 60.A-9450, 093.B-0368
BibCode: 2026A&A...705A.235S

Context. The Milky Way nuclear star cluster (MWNSC) is located in the Galactic centre, together with the Milky Way nuclear stellar disc (MWNSD), and they dominate the gravitational potential within the inner 300 pc. However, the formation and evolution of the two systems and their possible connections are still under debate. Aims. We reanalysed the low-resolution KMOS spectra in the MWNSC with the aim of improving the stellar parameters (T_eff, log g, and [M/H]) for the MWNSC. Methods. We used an improved line list, especially dedicated for cool M giants, that allowed us to improve the stellar parameters and to obtain in addition global α-elements. A comparison with high-resolution IR spectra (from IGRINS) gives very satisfactory results and constrains the uncertainties to T_eff ≃ 150 K, log g ≃ 0.4 dex, and [M/H] ≃ 0.2 dex. Our α-elements agree within 0.1 dex compared to the IGRINS spectra. Results. We obtained a high-quality sample of 1140 M giant stars where we see an important contribution of a metal-poor population (∼20%) centred at [M/H] ≃−0.7 dex, while the most dominant part comes from the metal-rich population with [M/H] ≃ 0.26 dex. We constructed a metallicity map and find a metallicity gradient of ∼−0.1 ± 0.02 dex/pc favouring the inside-out formation scenario for the MWNSC.

Characterising the post-red supergiant binary system AFGL 4106 and its complex nebula with SPHERE/VLT

First Author: Tomassini, G.
Instruments: SPHERE
ProgramIDs: 0102.D-0501, 1104.C-0416
BibCode: 2026A&A...706A...5T

Context. Mass loss in evolved massive stars plays a critical role in shaping their circumstellar environments and enriching the interstellar medium. In binary systems, stellar interactions can further complicate this process, affecting stellar evolution, stellar yields, and nebular morphology. Aims. We aim to characterise the physical and morphological properties of the binary system AFGL 4106, which is composed of two evolved massive stars. Understanding its mass-loss processes and circumstellar environment offers insight into the late stages of stellar evolution in massive binary systems. Methods. We obtained high-angular-resolution, high-contrast imaging using VLT/SPHERE with ZIMPOL (optical) and IRDIS (near-infrared) across multiple filters. We used aperture photometry to extract the spectral energy distributions (SEDs) of each star and applied radiative-transfer modelling to study the system and its surrounding dusty environment. Results. The observations resolve both components of the binary and unveil a complex, dusty nebula featuring asymmetric structures and cavities. SED fitting yields stellar temperatures of T₁ = 6723 ± 196 K and T₂ = 3394 ± 264 K, along with bolometric luminosities of L₁ = (7.9 ± 0.18)×10⁴ L_⊙ and L₂ = (3.8 ± 0.11)×10⁴ L_⊙. These values support the classification of the primary as being in a post-red-supergiant (post-RSG) phase and the secondary as an active red supergiant (RSG). The luminosity ratio, combined with the inferred radii, indicates that both stars are at close yet distinct stages of their evolution. The binary is surrounded by an extended shell whose asymmetric morphology and large-scale features suggest interaction with the stellar winds and interstellar medium (ISM), and possibly the presence of a third, undetected companion. Conclusions. These observations provide the first resolved view of AFGL 4106's system and its dusty envelope. Our analysis sets constraints on the physical properties and evolutionary status of the system. This work contributes to our understanding of mass-loss processes in massive binaries and the shaping of nebulae around evolved stars.

Unveiling the white dwarf in the eclipsing polar HU Aquarii

First Author: Schwope, A. D.
Instruments: ULTRACAM_VLT
ProgramIDs: 075.D-0349, 075.D-0135, 075.D-0738
BibCode: 2026A&A...706A..41S

We present an analysis of high-speed u- and r-band photometry of the eclipsing polar HU Aqr that was obtained with ULTRACAM mounted on the VLT. The observations were performed during a low state, permitting us for the first time to determine the contact points of the white dwarf. Using LCURVE we could determine its size, and hence mass, with a direct method and with unprecedented accuracy. We determined the mass of the white dwarf as 0.78 ± 0.02 M_⊙, the mass ratio Q = M_WD/M_sec = 4.59, and the orbital inclination i = 87.° 4 ± 0.° 9. An extended warm region with a central temperature of ∼33 000 K was observed in the u-band at the location of the previous high-state accretion spot. Weak accretion was ongoing in the low state that led to cyclotron emission that could best be studied with the r-band data. It has a diameter of only 3° to 4° and is located much closer to the binary meridian than the accretion-heated region studied in the u-band. The longitudinal shift of the two accretion regions is of order 30°, due to early and late coupling of accreted matter onto the magnetic field lines in low and high accretion states, respectively. The low-state cyclotron-emitting region has a vertical extent of 0.005 − 0.016 R_WD, a value that seems to be correlated to the instantaneous accretion rate.

Unveiling the 3D structure of the central molecular zone from stellar kinematics and photometry: The 50 and 20 km/s clouds

First Author: Nogueras-Lara, Francisco
Instruments: HAWKI, VIRCAM
ProgramIDs: 195.B-0283, 198.B-2004, 179.B-2002
BibCode: 2026A&A...706A..18N

Context. The central molecular zone (CMZ), surrounding the Galactic centre, is the largest reservoir of dense molecular gas in the Galaxy. Despite its relative proximity, the 3D structure of the CMZ remains poorly constrained, primarily due to projection effects. Aims. We aim to constrain the line-of-sight location of two molecular clouds in the CMZ - the 50 and 20 km/s clouds - and to investigate their possible physical connection using stellar kinematics and photometry. This study serves as a pilot for future applications across the full CMZ. Methods. We estimated the line-of-sight position of the clouds by analysing stellar kinematics, stellar densities, and stellar populations towards the cloud regions and a control field. Results. We find an absence of westward moving stars in the cloud regions, which indicates that they lie on the near side of the CMZ. This interpretation is supported by the stellar density distributions. The similar behaviour observed in the two clouds, as well as in the region between them (the ridge), suggests that they are located at comparable distances and are physically linked. We also identified an intermediate-age stellar population (2-7 Gyr) in both regions, consistent with that observed on the near side of the CMZ. We estimated the line-of-sight distances at which the clouds and the ridge become kinematically detectable (i.e. where the proper motion component parallel to the Galactic plane differs from that of the control field at the 3σ level) by converting their measured proper motions parallel to the Galactic plane using a theoretical model of the stellar distribution. We find that the 50 and 20 km/s clouds are located at 43 ± 8 pc and 56 ± 11 pc from Sgr A^*, respectively, and that the ridge lies at 56 ± 11 pc; this supports the idea that the clouds are physically connected through the ridge.

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): V721 CrA and BN CrA have wide and structured disks in the polarised infrared

First Author: Columba, G.
Instruments: ALMA_Band_6, SPHERE
ProgramIDs: 1104.C-0415, 2015.1.01301.S
BibCode: 2026A&A...706A..16C

Context. The environment within which stars form and evolve can play a crucial role in shaping their surrounding protoplanetary disks. This is the reason why homogeneous analyses of protoplanetary disks around young stars in the same star-forming region has become of great relevance in recent years. Aims. We present near-infrared scattered-light observations of the disks around two stars of the Corona Australis star-forming region, V721 CrA and BN CrA, obtained with VLT/SPHERE in the H band, as part of the DESTINYS large programme. Our objective is to analyse the morphology of these disks and highlight their main properties. Methods. We adopted an analytical axisymmetric disk model to fit the observations and performed a regression on key disk parameters, namely the dust mass, the height profile, and the inclination. We used RADMC-3D code to produce synthetic observations of the analytical models, with full polarised scattering treatment. Results. Both stars show resolved and extended disks with substructures in the near-IR. The disk of V721 CrA is vertically thicker, radially smaller (∼120 au), and brighter than that of BN CrA (∼190 au). It also shows spiral arms in the inner regions. The disk of BN CrA shows a dark circular lane, which could be either an intrinsic dust gap or a self-cast shadow, and a brightness enhancement along the disk minor axis. Both disks are compatible with the evolutionary stage of their parent subgroup within the CrA region: V721 CrA belongs to the on-cloud part of CrA, which is dustier, denser, and younger, whereas BN CrA is found on the outskirts of the older off-cloud group.

Constraining Nuclear Molecular Gas Content with High-resolution CO Imaging of GOALS Galaxies

First Author: Agostino, James
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2017.1.01235.S, 2018.1.01123.S, 2019.1.00811.S
BibCode: 2026ApJ...998..343A

We present measurements of the cool molecular gas mass around the nuclei of two gas-rich mergers, III Zw 035 and IRAS F01364−1042, whose enclosed masses (M_enc) within the central 40─80 pc would be overmassive if attributed entirely to the supermassive black hole (SMBH) mass and compared to SMBH─galaxy scaling relations. Our gas mass measurements are derived from Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 long-baseline observations of CO(J = 2─1) and 230 GHz continuum emission at 14─20 pc resolution, which probes below the resolving limit of the previous black hole mass measurements. Subtracting molecular gas mass from these enclosed masses is not enough to reconcile with black hole─galaxy relationships, but independently measuring M_enc using the cold CO(2─1) gas does shift the black holes down to their expected values. Still, these ALMA data reveal respective molecular gas masses of ∼3 × 10⁷ to ∼6 × 10⁸ M_⊙ within 70 pc of these black holes, which could challenge some black hole accretion models that assume nuclear gas like this has no angular momentum.

A surprisingly large asymmetric ejection from Mira A

First Author: Khouri, T.
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.00191.S, 2018.1.00749.S, 2022.1.01071.S
BibCode: 2026A&A...707A.162K

Context. Stars with masses between roughly 1 and 8 M_⊙ end their lives on the asymptotic giant branch (AGB), when intense mass loss takes place, with major consequences for the chemical evolution of the universe. The mechanism responsible for the outflows is generally accepted to be radiation pressure acting on dust grains that form in the dense extended atmospheres of AGB stars. Dust formation is enabled, or at least dramatically enhanced, by the action of convection and stellar pulsations. The complex physics underlying convection, stellar pulsations, and dust nucleation precludes predicting AGB mass loss from first principles. Aims. Our aim was to characterize the recent mass ejections of the AGB star Mira A using observations of the inner envelope. In particular, we studied two lobes observed to be expanding away from Mira A to obtain empirical insights into the mass-ejection process. Methods. We investigated the evolution of the lobes using images of polarized light obtained at six epochs using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) on the Very Large Telescope and of molecular emission at two epochs obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Six lines of SO₂ were used to investigate the excitation temperature and column density of SO₂ in the lobes. We used the ¹³CO J = 3-2 line and radiative transfer models to constrain the column density of the gas, which allowed us to infer the abundances of SO, SO₂, AlO, AlF, and PO in the lobes. Results. While dust seems confined almost exclusively to the edges of the lobes, gas fills the lobes and displays higher densities than expected at the observed radial distances based on the large-scale mass-loss rate of Mira A, with a total gas mass in the lobes of ∼2 × 10⁻⁵ M_⊙. We find the expansion of the lobes to be consistent with both a constant velocity (ejection time in 2010 or 2011) or a decelerating expansion (ejection time in 2012). If ejection events with a similar magnitude happen periodically, we derive periods between 50 and 200 years to account for the mass-loss rate of Mira A. This periodicity is very uncertain because of the complexity of the circumstellar environment that hampers accurate determinations of the mass-loss rate. We find abundances in the lobes of ∼1.5 × 10⁻⁶ and ∼2.5 × 10⁻⁶ for SO and SO₂, respectively, when accounting for radiative transfer effects and of 2 × 10⁻¹⁰, 6.5 × 10⁻¹⁰, and 4 × 10⁻⁷ for AlO, AlF, and PO assuming LTE and optically thin emission. The strong variation in brightness of the different features identified in the polarized-light images is puzzling. We suggest that an asymmetric stellar radiation field preferentially illuminates specific regions of the circumstellar envelope at a given time, producing a lighthouse-like effect.

Spatially Resolved, Multiphase Mass Outflows of the Seyfert 1 Galaxy NGC 3227

First Author: Falcone, Julia
Instruments: ALMA_Band_6
ProgramIDs: 2016.1.00254.S
BibCode: 2026ApJ...997...68F

We present spatially resolved mass outflow rates of the ionized and molecular gas in the narrow-line region of the Seyfert 1 galaxy NGC 3227. Using long-slit spectroscopy and [O III] imaging from from the Hubble Space Telescope's Space Telescope Imaging Spectrograph and Apache Point Observatory's Kitt Peak Ohio State Multi-Object Spectrograph, in conjunction with Cloudy photoionization models and emission-line diagnostics, we find a peak ionized mass outflow rate of Ṁion= 19.9 ± 9.2 M_⊙ yr⁻¹ at a distance of 47 ± 6 pc from the supermassive black hole (SMBH). Using archival data from the Gemini-North Near-infrared Field Spectrograph measuring H₂ 2.1218 μm emission, we find a maximum peak warm molecular outflow rate of ṀH2≤9×10−4 M_⊙ yr⁻¹ at a distance of 36 ± 6 pc from the SMBH. Using archival data from the Atacama Large Millimeter/submillimeter Array measuring CO(2─1) emission, we find a maximum peak cold molecular gas mass outflow rate of ṀCO≤ 23.1 M_⊙ yr⁻¹ at a distance of 57 ± 6 pc from the SMBH. For the first time, we calculate spatially resolved gas evacuation timescales for the cold molecular gas reservoirs ostensibly sourcing the outflows, and find that gas evacuating to ∼400 pc from the SMBH occurs on timescales of 10^6.0─10^7.6 yr. These results indicate that the multiphase active galactic nucleus (AGN) outflows are effective in clearing the inner few hundred parsecs of NGC 3227's gas content on timescales that may set the AGN duty cycle of 10⁵─10⁸ yr.

The Atacama Cosmology Telescope: Observations of supermassive black hole binary candidates: Strong sinusoidal variations at 95, 147, and 225 GHz in PKS 2131─021 and PKS J0805─0111

First Author: Hincks, Adam D.
Instruments: ALMA_Band_3, ALMA_Band_7
ProgramIDs: 2011.0.00001.CAL
BibCode: 2026A&A...706A.206H

Large sinusoidal variations in the radio light curves of the blazars PKS J0805─0111 and PKS 2131─021 have recently been discovered with an 18-year monitoring programme at the Owens Valley Radio Observatory, making these systems strong supermassive black hole binary (SMBHB) candidates. The sinusoidal variations in PKS 2131─021 dominate its light curves from 2.7 GHz to optical frequencies. We report sinusoidal variations observed in both objects with the Atacama Cosmology Telescope (ACT) at 95, 147, and 225 GHz consistent with the radio light curves. The ACT 95 GHz light curve of PKS 2131─021 agrees well with the contemporaneous 91.5 GHz ALMA light curve and is comparable in quality, while the ACT light curves of PKS J0805─0111, for which there are no ALMA or other millimetre light curves, show that PKS 2131─021 is not an isolated case, and that this class of AGN exhibits the following properties: (a) the sinusoidal pattern dominates over a broad range of frequencies; (b) the amplitude of the sine wave compared to its mean value is monochromatic (i.e. nearly constant across frequencies); (c) the phase of the sinusoid phase changes monotonically as a function of frequency; (d) the sinusoidal variations are intermittent. We describe a physical model for SMBHB systems, the modified Kinetic Orbital model, that explains all four of these phenomena. The monitoring of ∼8000 blazars by the Simons Observatory over the next decade should provide a large number of SMBHB candidates that will shed light on the nature of the nanohertz gravitational-wave background.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): VIII. A dust arc and non-Keplerian gas kinematics in HD 121617

First Author: Marino, S.
Instruments: ALMA_Band_7, SPHERE
ProgramIDs: 0101.C-0420, 2022.1.00338.L
BibCode: 2026A&A...705A.202M

Context. ExoKuiper belts around young A-type stars often host CO gas, whose origin is still unclear. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) includes six of these gas-bearing belts, to characterise their dust and gas distributions and investigate the gas origin. Aims. As part of ARKS, we observed the gas-rich system HD 121617 with a 0_⋅^'' 12 (14 au) resolution and discovered an arc of enhanced dust density. In this paper, we analyse in detail the dust and gas distributions and the gas kinematics of this system. Methods. We extracted radial and azimuthal profiles of the dust (in the millimetre and near-infrared) and gas emission (¹²CO and ¹³CO) from reconstructed images. To constrain the morphology of the arc, we fitted an asymmetric model to the dust emission. To characterise the gas kinematics, we fitted a Keplerian model to the velocity map and extracted the gas azimuthal velocity profile by deprojecting the data. Results. We find that the dust arc is narrow (1─5 au wide at a radius of 75 au), azimuthally extended with a full width at half maximum of ~90°, and asymmetric; the emission is more azimuthally compact in the direction of the system's rotation, and represents 13% of the total dust mass (0.2 M_⊕). From analysis of the scattered light and CO images, we conclude that the arc is much less pronounced or absent for small grains and gas. Finally, we find strong non-Keplerian azimuthal velocities at the inner and outer wings of the ring, as was expected due to strong pressure gradients. Conclusions. The dust arc resembles the asymmetries found in protoplanetary discs, often interpreted as the result of dust trapping in vortices. If the gas disc mass is high enough (≳20 M_⊕, requiring a primordial gas origin), both the radial confinement of the ring and the azimuthal arc may result from dust grains responding to gas drag. Alternatively, it could result from planet-disc interactions via mean motion resonances. Further studies should test these hypotheses and may provide a dynamical gas mass estimate in this CO-rich exoKuiper belt.

Sunyaev─Zeldovich detection of hot intracluster gas at redshift 4.3

First Author: Zhou, Dazhi
Instruments: ALMA_Band_3
ProgramIDs: 2015.1.01543.T, 2017.1.00273.S, 2022.1.00495.S, 2023.1.00124.S
BibCode: 2026Natur.649.1130Z

Most baryons in present-day galaxy clusters exist as hot gas (≳10⁷ K), forming the intracluster medium (ICM)¹. Cosmological simulations predict that the mass and temperature of the ICM decline towards earlier times, as intracluster gas in younger clusters is still assembling and being heated^{2, 3─4}. To date, hot ICM has been securely detected only in a few systems at or above z ≍ 2, leaving the timing and mechanism of ICM assembly uncertain^{5, 6─7}. Here we report the direct observation of hot intracluster gas via its thermal Sunyaev─Zeldovich signature in the protocluster SPT2349─56 with the Atacama Large Millimeter/submillimeter Array. SPT2349─56 hosts a large molecular gas reservoir and three radio-loud active galactic nuclei (AGN) within an approximately 100-kpc region at z = 4.3 (refs. ^{8, 9, 10─11}). The measurement implies a thermal energy of about 10⁶¹ erg in the core, about 10 times more than gravity alone should produce. Contrary to current theoretical expectations^3,4,12, the hot ICM in SPT2349─56 demonstrates that substantial heating can occur very early in cluster assembly, depositing enough energy to overheat the nascent ICM well before mature clusters become common at z ≍ 2.

The circumbinary disk of HD34700A: I. CO gas kinematics indicate spirals, infall, and vortex motions

First Author: Stadler, J.
Instruments: ALMA_Band_6
ProgramIDs: 2022.1.00760.S
BibCode: 2026A&A...707A.160S

Aims. We present the first high-resolution (∼0″.14) Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 dust continuum, ¹²CO J = 2-1, ¹³CO J = 2-1, and C¹⁸O J = 2-1 molecular line emission observations of the quadruple system HD 34700. In particular, HD34700AaAb is a spectroscopic binary (M_bin = 4 M_⊙) surrounded by two low-mass companions (B = 0.6 M_⊙, C = 0.4 M_⊙) at large separations. Its circumbinary disk is highly substructured, featuring numerous spiral arms and a large cavity observed in infrared (IR) scattered light. We aim to shed light on the nature of these features by examining the gas kinematics at work in the circumbinary disk. Methods. We analyzed the CO line channel and intensity moment maps. By fitting a Keplerian model to the line channel emission, we identified the residual motions and conducted a line spectra analysis. Results. We resolved an asymmetric continuum crescent on top of a dust ring at 0739 (138 au) colocated with the IR ring. The CO molecule's line emission traces a smaller cavity in gas, whose edge aligns with the inner rim of the ring detected in Hα emission at 0″.20 (65 au). The ¹²CO line emission and kinematics trace highly non-Keplerian motions (∼0.1∆υ_k) and these CO spiral features align well with the spiral structures in scattered light. The ¹²CO line spectra analysis reveals a streamer above the southeastern disk plane, likely falling onto the disk. The ¹³CO and C¹⁸O kinematics largely follow the disk's underlying Keplerian rotation, while ¹³CO exhibits tentative signs of anticyclonic vortex flows at the continuum crescent location. Conclusions. Our multimolecular line study suggests that the circumbinary disk of HD 34700A is highly perturbed in its upper layers, possibly warped and influenced by infalling material. While late-stage infall may account for the IR spirals and the formation of the vortex through Rossby wave instability, an embedded massive companion within the cavity might also be contributing to these features.

Magnetic threads and gravity: ALMA observations of the infrared dark cloud G14.225-0.506

First Author: Añez-López, Nacho
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00793.S
BibCode: 2026A&A...707A.165A

Context. In the star formation process, the interplay between gravity, turbulence, and magnetic fields is significant, with magnetic fields apparently serving a regulatory function by opposing gravitational collapse. Nonetheless, the extent to which magnetic fields are decisive relative to turbulence and gravity, as well as the specific environments and conditions involved, remains uncertain. Aims. This study aims to ascertain the role of magnetic fields in the fragmentation of molecular clouds into clumps down to core scales. Methods. We examined the magnetic field as observed with ALMA at core scales (approximately 10 000 AU/0.05 pc) toward the infrared dark cloud (IRDC) G14.225-0.506, focusing on three regions with shared physical conditions. We juxtaposed these data with prior observations at the hub-filament system scale (approximately 0.1 pc). Results. Our findings indicate a similar magnetic field strength and fragmentation level between the two hubs. However, distinct magnetic field morphologies have been identified across the three regions where the polarized emission is detected. In region N (i.e., the northern Hub: Hub-N), the large-scale magnetic field, perpendicular to the filamentary structure, persists at smaller scales in the southern half; however, it becomes distorted near the more massive condensations in the northern half. Notably, these condensations exhibit signs of impending collapse, as evidenced by supercritical mass-to-flux values. In the region S (i.e., the southern Hub: Hub-S), the magnetic field is considerably inhomogeneous among the detected condensations and we did not observe a direct correlation between the field morphology and the condensation density. Lastly, in an isolated dust clump located within a southern filament of Hub-N, the magnetic field aligns parallel to the elongated emission, suggesting a transition in the field geometry. Conclusions. The magnetic field shows a clear evolution with spatial scales. We propose that the most massive condensations detected in Hub-N are undergoing gravitational collapse, as revealed by the relative significance of the magnetic field and gravitational potential (Σ_B) and mass-to-flux ratio. The distortion of the magnetic field could be a response to the flow of material as a result of such a collapse.

Digging into the Interior of Hot Cores with ALMA (DIHCA). VI. The Formation of Low-mass Multiple Systems in High-mass Cluster-forming Regions

First Author: Luo, Qiu-yi
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00237.S, 2017.1.00101.S, 2018.1.00105.S, 2016.1.01036.S
BibCode: 2026ApJ...999..192L

Most stars form in multiple systems, with profound implications in numerous astronomical phenomena intrinsically linked to multiplicity. However, our knowledge about the process of how multiple stellar systems form is incomplete and biased toward nearby molecular clouds forming only low-mass stars, which are unrepresentative of the stellar population in the Galaxy. Most stars form within dense cores in clusters alongside high-mass stars (>8 M_⊙), as the Sun likely did. Here we report deep Atacama Large Millimeter/submillimeter Array (ALMA) 1.33 mm dust continuum observations at ∼160 au spatial resolution, revealing 72 low-mass multiple systems embedded in 23 high-mass cluster-forming regions, as part of the Digging into the Interior of Hot Cores with ALMA survey. We find that the companion separation distribution presents a distinct peak at ∼1200 au, in contrast to the one at ∼4000 au observed in nearby low-mass regions. The shorter fragmentation scale can be explained by considering the higher pressure exerted by the surrounding medium, which is higher than the one in low-mass regions, due to the larger turbulence and densities involved. Because the peak of the companion separation distribution occurs at much larger scales than the expected disk sizes, we argue that the observed fragmentation is produced by turbulent core fragmentation. Contrary to predictions, the multiplicity fraction remains constant as the stellar density increases. We propose that in the extremely dense environments where high-mass stars form, dynamical interactions play an important role in disrupting weakly bound systems.

A Monopolar Jet from Protostar HOPS 10: Evidence for Asymmetric Magnetized Launching

First Author: Dutta, Somnath
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2015.1.00041.S, 2018.1.00302.S
BibCode: 2026AJ....171..211D

A fundamental challenge in star formation is understanding how a protostar accretes mass from its circumstellar disk while removing excess angular momentum. Protostellar jets are widely invoked as the primary channels for angular-momentum removal, yet the mechanism by which they are launched and extract angular momentum remains poorly constrained. Here, we report high-resolution Atacama Large Millimeter/submillimeter Array Band 7 (345 GHz) and Band 6 (230 GHz) observations of ¹²CO (3─2), ¹²CO (2─1), and SiO (5─4) emission from the protostar HOPS 10 (G209.55−19.68S2). The combined data trace both the entrained outflow and the collimated jet with excellent spatial and velocity resolution, revealing a uniquely monopolar protostellar jet—the clearest example reported to date. The system exhibits a distinctly unipolar high-velocity jet (velocity offset, VHV,off=Vobserved−Vsystemic = +44 to +66 km s⁻¹), unlike the predominantly bipolar morphology characteristic of most protostellar jets. While the low-velocity outflow (velocity offset, V_LV,off = V_observed − V_systemic = −20 to +30 km s⁻¹) is detected in both directions, the high-velocity jet appears only on one side, and this monopolarity is consistent across all tracers. Given the nearly edge-on geometry and low submillimeter extinction, comparable emission would normally be expected from both lobes. The shock tracer SiO emission confirms a genuine, highly collimated jet rather than cloud contamination, and no ambient structure is capable of obscuring a counterjet. We argue that intrinsically asymmetric mass loading along the disk's magnetic field lines provides the most plausible explanation for the observed monopolarity.

Physical and Chemical Characterization of GY 91's Multi-ringed Protostellar Disk with ALMA

First Author: Jiang, Sally D.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2018.1.00028.S, 2021.1.01588.S
BibCode: 2026ApJ..1000...35J

GY 91, commonly categorized as a Class I young stellar object, is notable for disk dust substructures that have been hypothesized to trace early planet formation. Using the Atacama Large Millimeter/submillimeter Array 12 m and Atacama Compact Array, we present new Band 7 dust continuum and molecular line observations of GY 91 at an angular resolution of ∼0.″3 (40 au). We report detections of CS J = 6─5, N₂H⁺ J = 3─2, C¹⁸O J = 3─2, H₂CS JKa,Kc=81,7−71,6 , H₂CO JKa,Kc=40,4−30,3 , and H₂CO JKa,Kc=42,3−32,2 , as well as a tentative detection of ¹³C¹⁸O J = 3─2. We observe azimuthal asymmetry in CS and H₂CS emission, as well as radially structured H₂CO 4_0,4─3_0,3 emission outside the dust continuum. C¹⁸O and H₂CO 4_0,4─3_0,3 show significant cloud contamination, while CS and N₂H⁺ are good tracers of Keplerian rotation originating from the disk. Envelope emission does not appear to contribute significantly either to the continuum or molecular line observations. GY 91's chemical properties appear in large part to resemble those of Class II disks, although observations of additional molecular probes should be obtained for a fuller comparison. With CS, we estimated a dynamical stellar mass of 0.58 M_⊙, which is higher than previous estimates from stellar evolutionary models (0.25 M_⊙). Using both radiative transfer modeling of the dust continuum and comparison of the C¹⁸O and N₂H⁺ fluxes to literature thermochemical models, we estimate a disk mass of ∼0.01 M_⊙.

A JWST NIRCam/MIRI View of the W51A High-mass Star-forming Region

First Author: Yoo, Taehwa
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2015.1.01596.S, 2017.1.00293.S
BibCode: 2026AJ....171..208Y

We present observations of the W51A region, including the massive protoclusters W51-E and W51-IRS2, with JWST in 10 NIRCam and 5 MIRI filters. In this work, we highlight the most novel features apparent in these images and compare them with other multiwavelength images. The broad view of the NIRCam/MIRI images of the W51A region shows that areas dominated by warm dust and ionized gas are distinct from those dominated by polycyclic aromatic hydrocarbons. The high angular resolution of the JWST images resolves dust filaments in high contrast, revealing geometrically converging features feeding W51-E and a cavity around W51-IRS2. This picture adds support to the hypothesis that feedback from W51-IRS2 is suppressing further gas infall onto the protocluster, while by contrast, gas is still accreting onto W51-E. Comparing the NIRCam and MIRI images to Atacama Large Millimeter/submillimeter Array (ALMA) data, we find 24 sources detected by both JWST and ALMA, accounting for only ∼10% of the ALMA sources; the rest are too embedded or too cool to be detected by JWST. A knot of [Fe II] and H₂ emission north of W51-IRS2, previously detected in ground-based images, reveals peculiarly bright and compact peaks detected in all JWST bands. The knot is likely the most energetic example of a protostellar jet driven by a massive star impacting dense interstellar medium. The new images provide a complementary view to the previous long-wavelength perspective on this 4 × 8 pc area of one of the most active star-forming regions in our Galaxy, revealing new mysteries to be further explored.

The ALMaQUEST Survey. XVII. Unveiling Multiple Quenching Pathways in Green Valley Galaxies via Molecular Gas and Quenching Timescale Analyses

First Author: Lin, Lihwai
Instruments: ALMA_Band_3
ProgramIDs: 2015.1.01225.S, 2017.1.01093.S, 2018.1.00558.S, 2018.1.00541.S, 2019.1.00260.S, 2019.1.01136.S, 2019.1.01178.S
BibCode: 2026ApJ...999..263L

Statistically, green valley (GV) galaxies exhibit lower molecular gas fractions (f_gas) and reduced star formation efficiency (SFE) compared to star-forming galaxies. However, it remains unclear whether quenching is primarily driven by one factor or results from a combination of mechanisms in individual GV galaxies. In this study, we address this question by examining the spatial distributions of star formation and molecular gas in 28 GVs selected from the ALMaQUEST survey and additional literature samples. For each galaxy, we identify regions with suppressed specific star formation rate (sSFR) and measure ∆f_gas and ∆SFE—offsets from the resolved scaling relations of the star-forming main-sequence galaxies. By comparing the fraction of regions with negative ∆f_gas and ∆SFE, we classify 35.7% ± 13.2% (57.1% ± 17.9%) of GV galaxies as f_gas driven, 39.3% ± 14.0% (39.3% ± 14.0%) as SFE driven, and 25.0% ± 10.6% (3.6% ± 3.6%) as mixed mode when adopting a fixed (variable) CO-to-H₂ conversion factor (α_CO). These results indicate that GVs undergo quenching through multiple pathways. As sSFR decreases from the main sequence to the GV, we observe a transition toward predominantly SFE-driven quenching, possibly linked to internal processes such as morphological quenching or active galactic nucleus activity. We further estimate the quenching timescale (τ_decay), defined as the time from the peak star formation rate to 1 e^─1 (approximately 37%) of its value, using integrated MaNGA spectra. SFE-driven quenching is typically associated with short τ_decay, while f_gas-driven quenching shows a broader range. Overall, 75% of GVs exhibit τ_decay shorter than 1 Gyr, suggesting that quenching in most GVs proceeds rapidly, challenging purely slow-quenching scenarios like starvation.

Detailed lens modeling and kinematics of the submillimeter galaxy G09v1.97: An analysis of CO, H₂O, H₂O⁺, and dust continuum emission

First Author: Kade, K.
Instruments: ALMA_Band_4
ProgramIDs: 2015.1.01320.S, 2018.1.01710.S
BibCode: 2026A&A...707A.252K

Context. While the formation mechanisms of intensely starbursting galaxies at high redshift remain unknown, one possible mechanism for producing these intense rates of star formation is via mergers and interactions. However, detecting these at high redshift remains a challenge. Observations of high-redshift gravitationally lensed galaxies provide a way to study the interstellar medium and environment of these extreme starbursts in detail. Aims. We aim to use high angular resolution observations of dust continuum, CO(6−5), H₂O(2₁₁ − 2₀₂), and H₂O⁺(2₀₂ − 1₁₁) emission to constrain the ongoing processes in the z = 3.63 gravitationally lensed submillimeter galaxy H-ATLAS J083051.0+013224 (G09v1.97). Methods. We used the sophisticated lens modeling software PYAUTOLENS to perform both parametric and nonparametric source modeling. We created a demagnified source plane CO(6−5) emission line cube and performed the kinematic modeling using ^3DBAROLO. Additionally, we investigated the properties of the continuum and molecular line emission in the source plane. Results. We find that the regions of CO(6−5) and H₂O(2₁₁ − 2₀₂) emission are closely matched in the source plane, but that the dust continuum emission is more compact. We find that our lens modeling results do not require more than one source, contrary to what has been found in previous studies. Instead, we find that G09v1.97 resembles a rotating disk with V_max/σ̄ = 2.8 ± 0.4 V max / σ ̄ = 2.8 ± 0.4 , along with evidence of residual emission indicative of noncircular motions such as outflows, tidal tails, or an additional background galaxy. Conclusions. We suggest that the origin of the noncircular motions might be associated with a biconical outflow or a tidal tail from an interaction; alternatively, this might indicate the possible presence of an additional galaxy. We calculated the dynamical mass, gas mass, star formation rate, and depletion time for G09v1.97, along with a high star formation rate and low gas depletion time. In combination, this suggests that G09v1.97 has recently undergone an interaction, triggering intense star formation, while also being in the process of settling into a disk.

A persistent bow shock in a diskless magnetized accreting white dwarf

First Author: Iłkiewicz, Krystian
Instruments: MUSE
ProgramIDs: 112.25LQ
BibCode: 2026NatAs..10..391I

Stellar bow shocks form when an outflow interacts with the interstellar medium. In white dwarfs accreting from a binary companion, outflows are associated with strong winds from the donor star, the accretion disk or a thermonuclear runaway explosion on the white dwarf surface. To date, only six accreting white dwarfs are known to harbour disk-wind-driven bow shocks that are not associated with thermonuclear explosions. Here we report the discovery of a bow shock associated with a high-proper-motion diskless accreting white dwarf, 1RXS J052832.5+283824. We show that the white dwarf has a strong magnetic field in the range B ≈ 42-45 MG, making RXJ0528+2838 a bona fide known polar-type cataclysmic variable harbouring a bow shock. The resolved bow shock is shown to be inconsistent with a past thermonuclear explosion or with being inflated by a donor wind, ruling out all accepted scenarios for inflating a bow shock around this system. Modelling of the energetics reveals that the observed bow shock requires a persistent power source with a luminosity significantly exceeding the system accretion energy output. This implies the presence of a powerful, previously unrecognized energy-loss mechanism—potentially tied to magnetic activity—that may operate over sufficiently long timescales to influence the course of binary evolution.

Where Do Stars Explode in the ISM?—The Distribution of Dense Gas around Evolved Massive Stars in M33

First Author: Sarbadhicary, Sumit K.
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00901.S, 2019.1.01182.S, 2018.1.00378.S
BibCode: 2026ApJ..1000...70S

The effect of supernovae (SNe) on star formation in the interstellar medium (ISM) depends sensitively on where SNe explode with respect to ISM clouds. Observationally, SN ISM environments characterized by spatially resolved gas maps can empirically guide the placement of SNe in subgrid models, but unfortunately such measurements remain scarce, as SNe are rare and often distant. Here we demonstrate a new approach—mapping the ISM around evolved massive stars that are soon to explode. These provide a substantially larger sample of "explosion sites" (than just historical SNe) in nearby galaxies that have high-resolution atomic and molecular ISM maps from the Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. We demonstrate this technique in the well-resolved Local Group spiral M33 by analyzing the 50 pc scale projected ISM densities around red supergiants (RSGs; 8─30 M_⊙stars) Wolf─Rayet stars (W-Rs; >30M_⊙stars), and supernova remnants. We find a mass-dependent correlation between stars and gas clouds, with at least 45% of W-Rs and up to 77% of RSGs having no detectable H₂ at their pixel locations. In the sample with H₂ detections, we find that more-massive younger progenitors are coincident with denser gas. We show that the density distributions for stars >15 M_⊙are statistically distinct from random alignment of stars and gas in M33. Our work provides the first observationally derived estimate of the fraction of the SN-producing stellar population correlated with ISM density peaks. We demonstrate how this can be compared with galaxy simulations, and advocate similar comparisons to the community for constraining subgrid models.

The turbulence driving mode in NGC7793 and NGC1313

First Author: Miller, Lewis J.
Instruments: ALMA_Band_6
ProgramIDs: 2015.1.00782.S
BibCode: 2026MNRAS.547ag359M

We present spatially resolved measurements of turbulence driving modes across entire extragalactic discs of NGC7793 and NGC1313, using Atacama Large Millimetre/submillimetre Array (ALMA) CO (J = 2─1) observations at

$13\, \mathrm{pc}$

resolution. By applying a kernel-based analysis of density and velocity fluctuations, we map the turbulence driving parameter, b, which characterises the balance between solenoidal (

$b\sim 0.3$

) and compressive (

$b\sim 1$

) turbulent driving regimes. b is quantified as the ratio of the turbulent density fluctuations relative to the turbulent sonic Mach number,

$\mathcal {M}$

. Both galaxies show predominantly solenoidal driving on average for the regions where we find valid results (

$b\ge 0.33(\pm 0.05)^{+0.14}_{-0.10}$

in NGC7793;

$b\ge 0.24(\pm 0.03)^{+0.10}_{-0.07}$

in NGC1313), noting that this is without including the influences of magnetic fields, making these measurements lower limits. We find substantial spatial variation of b, including localized regions of strongly compressive driving. NGC1313 exhibits higher turbulent Mach numbers and density dispersions than NGC7793, consistent with the disturbed morphology and recent satellite interaction in NGC1313. The turbulence in both NGC7793 and NGC1313 is supersonic (

$3\lesssim \mathcal {M}\lesssim 20$

), and NGC1313 shows a radially decreasing trend of

$\mathcal {M}$

with galactocentric radius. Radial trends indicate more solenoidal driving in the galaxy centres, potentially reflecting enhanced shear, and increasingly compressive modes in the outskirts. These results demonstrate that turbulence driving varies systematically with galactic environment and cannot be assumed uniform across discs. Our study applies a previously established method to larger scales and new data, linking local turbulence physics to global star formation regulation in galaxies, providing a new avenue for testing theoretical models with future integral field units (IFU) and ALMA surveys.

Spatial distribution of organics in the Horsehead nebula: Signposts of chemistry driven by atomic carbon

First Author: Hernández-Vera, Claudio
Instruments: ALMA_Band_3
ProgramIDs: 2016.2.00027.S
BibCode: 2026A&A...707A.120H

Complex organic molecules (COMs) are considered essential precursors to prebiotic species in the interstellar and circumstellar medium. Despite their astrobiological relevance, many aspects of the formation of COMs remain unclear, particularly the role of ultraviolet (UV) radiation. While COMs were once expected to be efficiently destroyed under UV-irradiated conditions, detections in photodissociation regions (PDRs) have challenged this view. However, the mechanisms by which UV radiation contributes to their formation are still uncertain. Here we present moderately resolved maps of simple and complex organic molecules at the UV-illuminated edge of the Horsehead nebula, obtained by combining Atacama Large Millimeter/submillimeter Array (ALMA) and IRAM 30 m single-dish observations at ~15″ resolution. For the first time in this PDR environment, we analyzed the spatial distribution of species such as C¹⁷O, CH₂CO, CH₃CHO, HNCO, CH₃CN, and HC₃N. By incorporating previous C¹⁷O and C¹⁸O single-dish data as well as Plateau de Bure Interferometer (PdBI) maps of H₂CO and CH₃OH, we derived profiles of gas density, temperature, thermal pressure, and column densities of the organic species as a function of distance from the UV source. Our results show that most organic species ─ particularly H₂CO, CH₂CO, CH₃CHO, HNCO, and CH₃CN ─ exhibit enhanced column densities at the UV-illuminated edge compared to cloud interiors, possibly indicating efficient dust-grain surface chemistry driven by the diffusion of atomic C and radicals produced via photodissociation of CO and CH₃OH, as supported by recent laboratory experiments. The exceptions, HC₃N and CH₃OH, can be attributed to inefficient formation on dust grains and ineffective nonthermal desorption into the gas phase, respectively. Additionally, contributions from gas-phase hydrocarbon photochemistry, possibly seeded by grain-surface products, cannot be ruled out. Further chemical modeling is needed to confirm the efficiency of these pathways for the studied species, which could have important implications for other cold UV-irradiated environments such as protoplanetary disks.

ATOMS-QUARKS Survey: Inflow and Infall in Massive Protocluster G318.049+00.086— Evidence of Competitive Accretion

First Author: Gupta, Shivani
Instruments: ALMA_Band_3, ALMA_Band_7
ProgramIDs: 2019.1.00685.S, 2017.1.00545.S
BibCode: 2026ApJ...999..180G

We present a gas kinematic study of the massive protocluster G318.049+00.086. The protocluster is reported to contain 12 prestellar core candidates and four protostellar cores. Filamentary structures are identified using the 1.3 mm dust continuum map, with four of them converging into a dense central region, forming a hub-filament system. High velocity gradients (10─20 km s⁻¹ pc⁻¹) derived from position─velocity analysis of H¹³CO⁺ emission along three of those filaments are suggestive of mass inflow onto the central hub. A mass inflow rate higher than 10³ M_⊙ Myr⁻¹ along the filaments indicates that the central hub is capable of forming massive star(s). Investigation of H¹³CO⁺ and CCH spectral profiles revealed the majority of the cores having the characteristic blue asymmetric line profiles, a typical signature of gravitational collapse. The remaining few cores showed red asymmetric profiles, indicative of gas expansion. Also, the derived mass infall rates for the protostellar cores in the hub region are significantly higher in comparison to those located along the filaments. The mass─radius relation of the cores revealed that the cores with red profiles reside in the massive star formation regime. However, the global velocity gradient along the filaments suggests that these particular cores are losing material to the hub. Our results support a competitive accretion scenario of massive star formation where gas is expected to be funnelled from less gravitationally dominant cores to the cores located at the gravitationally favorable position.

Orbital Motions of Binaries in Orion South

First Author: Zapata, Luis A.
Instruments: ALMA_Band_3
ProgramIDs: 2018.1.01107.S
BibCode: 2026ApJ...999..219Z

We present high-angular resolution ( ≃0.″06 ) Very Large Array and Atacama Large Millimeter/submillimeter Array observations of Orion South separated by 15.52 yr. The purpose of this study was to search for orbital motions in three close ( ≃0.″1 ) binary systems in the region. We do not detect changes in the position angle of the binaries, but in two of the cases, we detect significant changes in their separation in the plane of the sky. We use these changes to estimate that the total mass of the binaries is in the ≃1─2 M_⊙ range. We also estimate the disk masses from the millimeter emission. The disk-to-stellar mass ratio is in the range of 0.04─0.18, values consistent with those expected for very early stellar evolution (Class 0) protostars.

Massive dusty multiphase outflow in local merger shows no sign of slowing on kiloparsec scales

First Author: Hagedorn, B.
Instruments: ALMA_Band_3, ALMA_Band_7, MUSE
ProgramIDs: 0103.B-0391, 2018.1.00888.S, 2013.1.00659.S
BibCode: 2026A&A...707A..77H

We use ALMA CO(1-0) observations and VLT/MUSE rest-frame optical data of the ultraluminous infrared galaxy (ULIRG) IRAS20100-4156 at z = 0.1297 to characterize its powerful outflow in multiple phases using tracers of cold molecular, ionized, and neutral atomic gas and dust as well. Our analysis uses the correspondence with the stellar velocity field to split the complex emission line profiles of the CO(1-0) line into components in gravitational and non-gravitational motion. We find a massive (8 × 10⁹ M_⊙) molecular outflow containing about 40% of the total molecular gas mass in the system. The outflow shows a bi-conical morphology centered on the brightest galaxy in the merger, oriented along its minor axis and extending to ∼5 kpc. This outflow has a characteristic velocity of 170 km/s, an outflow mass rate of 700 M_⊙/yr, a depletion time of 16 Myr, and energetics consistent with star formation as a driver. The neutral atomic and ionized gas phases traced by NaI absorption and Hα emission show counterparts to the blueshifted cold molecular outflow but are only 15% and 3% as massive. None of the three gas phases show any signs of slowing down over the extent at which we detected the outflow, suggesting an acceleration mechanism acting on the outflowing gas at kpc scales. We also detect 3.5 × 10⁷ M_⊙ of dust, traced by optical extinction in the MUSE data, in the blueshifted outflowing cold molecular gas. The ionization state of the non-outflowing gas is consistent with star formation, while the outflowing component shows shock-like ionization. We conclude that the multiphase outflow in IRAS20100-4156 originates in the southeast nucleus of the merger and is driven by the starburst activity there, with radiation pressure likely playing a significant role in its acceleration.

Bar-driven Shocks in NGC 1365 Revealed by the Most Luminous Extragalactic Class I Methanol Maser

First Author: Chen, Xi
Instruments: ALMA_Band_6, MUSE
ProgramIDs: 094.B-0321, 2021.1.01150.S
BibCode: 2026ApJ...999L..20C

We report the first detection of the 36.2 GHz (4₋₁ → 3₀ E) Class I methanol (CH₃OH) maser in the central region of the barred spiral galaxy NGC 1365. This detection using the Australia Telescope Compact Array establishes NGC 1365 as the host of the most luminous extragalactic Class I methanol maser known, with a total isotropic luminosity of 19.3 L_⊙. The maser emission is unambiguously localized to the southern arm of the circumnuclear starburst ring and exhibits a tight alignment with the bar-driven gas inflow lane. The striking absence of maser emission in the star formation and feedback-dominated northern arm reveals a fundamental bimodality within the ring. Combined with archival multiwavelength data, our results demonstrate that the maser traces low-velocity (∼25−30 km s⁻¹), nondissociative molecular shocks in the southern arm, where the gas is cold, dense, and subject to a weak radiation field. This work directly resolves the long-standing ambiguity between bar-driven shocks and stellar feedback, establishing the 36.2 GHz maser as a unique and powerful shock-specific diagnostic for extragalactic studies. It provides a novel tool to spatially pinpoint shock fronts and to disentangle the roles of gravitational dynamics and radiative feedback in shaping the extreme environments of galactic nuclei.

Digging into the Chemical Complexity in the Outer Galaxy: A Hot Molecular Core in Sh 2-283

First Author: Ikeda, Toki
Instruments: ALMA_Band_7
ProgramIDs: 2022.1.01270.S
BibCode: 2026ApJ...999..194I

The outer Galaxy (Galactocentric distance ≳13.5 kpc) serves as an excellent laboratory for investigating the chemical complexity in low-metallicity environments. Here we present the chemical analyses for the outer Galactic hot core Sh 2-283-1a SMM1 (D_GC = 15.7 kpc and Z ∼ 0.3 Z_⊙), recently detected by T. Ikeda et al. using the Atacama Large Millimeter/submillimeter Array. Toward this source, a variety of molecular species, including complex organic molecules (COMs; CH₃OH, ¹³CH₃OH, CH₂DOH, and CH₃OCH₃), are detected. The molecular abundances relative to CH₃OH are similar to those of another outer Galactic hot core, demonstrating that chemically rich hot cores exist in different regions of the outer Galaxy. We also compared molecular abundances among hot cores in the inner Galaxy, outer Galaxy, and Magellanic Clouds. This comparison revealed that the metallicity-corrected N(SO₂)/N(H₂) ratios of outer Galactic hot cores are significantly lower than those of the inner Galactic ones, while their N(CH₃OH)/N(H₂) ratios are similar. The Magellanic hot cores show different trends despite having metallicities similar to those of the outer Galaxy, indicating that the chemical complexity of hot cores is governed by environmental conditions (e.g., cosmic-ray intensity and dust temperature) rather than simple metallicity scaling. These environmental differences would also affect the production efficiency of COMs derived from CH₃OH, as the N(CH₃OCH₃)/N(CH₃OH) and N(C₂H₅OH)/N(CH₃OH) ratios in the outer Galactic sources are moderately lower than those of inner Galactic sources. The N(CH₂DOH)/N(CH₃OH) ratio of Sh 2-283-1a SMM1 is 1.5 −1.2+3.9 %, comparable to that of inner Galactic high-mass sources.

Older Ages for 23 Pre-main Sequence Stars in Upper Scorpius Using Dynamical-mass-constrained Stellar Evolutionary Models

First Author: Towner, A. P. M.
Instruments: ALMA_Band_7
ProgramIDs: 2019.1.00493.S
BibCode: 2026ApJ...999..145T

We present revised stellar ages for 23 pre-main-sequence (PMS) K- and M-type stars in the Upper Scorpius (Upper Sco) star-forming region, derived using stellar dynamical masses to constrain isochronal ages from five PMS stellar evolutionary models. We find that mass-constrained stellar ages for all model sets are more consistent with the older, ∼8─11 Myr age for Upper Sco derived using earlier-type stars. Additionally, applying the independent mass constraint to isochronal ages tends to (1) increase stellar ages for most model sets, and (2) decrease age scatter for individual sources between model sets. Models that account for global magnetic fields consistently provide the best match to our observations: they change comparatively little when the mass constraint is applied, and produce 9─10 Myr ages under both unconstrained and mass-constrained conditions. Most standard (nonmagnetic) models produce younger ages (3─5 Myr) when unconstrained, but older ages (6─9 Myr) when constrained by dynamical mass. Our results are consistent with recent literature findings that suggest median disk lifetimes may be ≳2× longer than previously thought.

Upper Limit on HF(1─0) Absorption in a Dusty Star-forming Galaxy at z = 6: Constraints on Early Fluorine Enrichment

First Author: Tsujita, Akiyoshi
Instruments: ALMA_Band_5
ProgramIDs: 2023.1.01281.S
BibCode: 2026ApJ...999L..14T

Wolf─Rayet (WR) stars have recently attracted attention as possible drivers of early chemical enrichment, including the production of fluorine, whose nucleosynthetic origin remains debated. To test the contribution of massive stars to fluorine production in the early Universe, we conducted Atacama Large Millimeter/submillimeter Array Band 5 spectroscopy of the HF(1─0) absorption line toward a dusty star-forming galaxy at z = 6.024. This galaxy has a known gas-phase metallicity and is too young for low-mass asymptotic giant branch stars to have contributed significantly, providing a clean environment to isolate massive-star yields. We do not detect significant HF absorption (∼2σ) and derive a conservative 5σ upper limit of NHF/NH2<2.2×10−9 . This limit is about an order of magnitude below typical local measurements, indicating inefficient fluorine enrichment ∼0.9 Gyr after the Big Bang. Comparison with chemical evolution models shows that our constraint is consistent with scenarios without WR yields at this epoch. Expanding the sample of HF absorption measurements in high-redshift galaxies with well-characterized metallicities will be crucial for tracing the onset of WR enrichment and fluorine production across cosmic time.

Spatially resolved star formation relations in local luminous infrared galaxies along the complete merger sequence

First Author: Sánchez-García, M.
Instruments: ALMA_Band_6
ProgramIDs: 2015.1.00714.S, 2013.1.00243.S, 2013.1.00271.S, 2017.1.00255.S, 2017.1.00395.S
BibCode: 2026A&A...707A.144S

We investigated the properties of the interstellar medium (ISM) at giant molecular cloud (GMC) scales (∼100 pc) in a sample of 27 nearby luminous infrared galaxies (LIRGs) spanning all interacting stages along the merger sequence, i.e. from isolated systems to late-stage mergers. In particular, we study the relations between star-formation (SF) and molecular gas surface density as a function of the interaction stage by (1) defining beam-sized (unresolved, line-of-sight) regions and (2) identifying actual gas clumps and physical structures within the galaxies. In total, we identify more than 4000 beam-sized CO-emitting regions defined on scales of ∼100 pc and more than 1000 molecular gas clumps in the sample. To map the distribution of molecular gas we used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the J = 2─1 CO transition, and to map the distribution of star formation we used the Hubble Space Telescope (HST) observations of the Paα or Paβ hydrogen recombination lines. We derived spatially resolved Kennicutt─Schmidt (KS) relations for each LIRG in the sample. When using beam-sized regions, we find that 67% of galaxies follow a single relation between Σ_SFR and Σ_H2. However, in the remaining galaxies, the relation splits into two branches ─ one characterised by higher Σ_SFR and Σ_H2, the other by lower value ─ indicating the presence of a duality in this relation. In contrast, when using physical gas clumps, the duality disappears and all galaxies show a single trend. These results provide two complementary perspectives when studying the star formation process. The first maximises the number statistics (beam-sized regions), and the second focuses on actual structures associated with gas clumps in which the measured sizes have a physical meaning. We also studied other ISM and clump properties as a function of the merger stage of the LIRG systems. We find that isolated galaxies and systems in early stages of interaction exhibit smaller amounts of gas and lower star formation rates (SFRs). As the merger progresses, however, the amount of gas in the central kiloparsecs of the galaxy undergoing the merger increases, along with the SFR, and the slope of the KS relation becomes steeper, indicating an increase in the SF efficiency of the molecular gas clumps. Clumps in late-stage mergers are predominantly located at small distances from the nucleus, confirming that most of the activity is concentrated in the central regions. Interestingly, the relation between the star formation efficiency and the boundedness parameter (which measures the effects of gravity against velocity dispersion) evolves from being roughly flat in the early stages of the merger to becoming positive in the final phases, indicating that clump self-gravity only starts to regulate the star formation process between the early and mid merger stages.

Direct Spectroscopic Confirmation of the Young Embedded Protoplanet WISPIT 2c

First Author: Lawlor, Chloe
Instruments: GRAVITY, SPHERE
ProgramIDs: 115.29HG, 114.27EK
BibCode: 2026ApJ..1000L..38L

WISPIT 2 is a nearby young star with a multiringed disk that was recently confirmed to host a ∼4.9 M_Jup gas giant planet embedded in a large (60 au) gap at a radial separation of 57 au from the host star. We confirm and characterize a second, close-in planet in the WISPIT 2 system using a combination of new Very Large Telescope/SPHERE H-band dual-polarization imaging and VLTI/GRAVITY K-band interferometric observations of the WISPIT 2 system. The GRAVITY detection is consistent with a point-like source while its extracted K-band spectrum shows CO band-head absorption at 2.3 μm and a continuum shape consistent with a young giant planet. From the GRAVITY data, we extract a medium resolution K-band spectrum of the companion and fit atmospheric model grids using the species tool with nested sampling to constrain its effective temperature, radius, and luminosity. We infer T_eff of 1500─2600 K, a radius of 0.91─2.2 R_Jup, and a luminosity of (−3.47)─(−3.63). Comparison with evolutionary tracks implies a mass range of 8─12 M_Jup, approximately twice as massive as the previously confirmed WISPIT 2b. The astrometry rules out a background source and marginally detects orbital motion of WISPIT 2 c, which needs further follow-up observations for confirmation. WISPIT 2 now becomes an analog to PDS 70, offering a second laboratory for studying the formation and early evolution of a multiplanet system within its natal disk.

The Chemical Diversity of Giant-planet Nurseries as Revealed by ALMA

First Author: Booth, Alice S.
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_5, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2011.0.00318.S, 2012.1.00303.S, 2012.1.00631.S, 2013.1.00305.S, 2013.1.00498.S, 2015.1.00657.S, 2016.1.00340.S, 2016.1.00344.S, 2016.1.00826.S, 2016.1.00884.S, 2016.A.00026.S, 2017.1.00492.S, 2017.1.00845.S, 2017.1.01404.S, 2017.1.01424.S, 2017.1.01545.S, 2018.1.01055.L, 2018.1.01429.S, 2021.1.00690.S, 2021.1.00738.S, 2021.1.01123.L, 2023.1.00252.S, 2023.1.00628.S, 2024.1.00446.S
BibCode: 2026AJ....171..128B

With the giant exoplanet occurrence rate peaking around stars of 1.5─2.0 solar masses (M_⊙), there is strong motivation to characterize the disks that set their formation conditions. Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) allow us to investigate both the availability of different molecules in disks and infer the radial distribution of elemental abundances, enabling us to make connections to exoplanet systems. Here we present a survey of six transition disks around young F-, A-, and B-type stars using ALMA. We find ¹³C¹⁸O, CS, SO, and H₂CO in all six systems, as well as 10 additional molecules in a subset of disks, including detections of H₂S, ³³SO, and CH₃OCH₃. Using these data, and literature data where available, we construct the first comprehensive picture of Herbig disk chemistry. We find clear correlations between molecular tracers of C/O > 1 environments (e.g., CS, C₂H) and disk mass, as traced by C¹⁸O line flux. In contrast, tracers of C/O < 1 environments (e.g., SO, CH₃OH) do not show significant correlations with disk mass. Interestingly, these molecules are relatively brighter in lower-mass disks, with their presence primarily linked to disks with central cavities and spirals. Finally, we show that the observed chemical diversity seen across Herbig disks leads to varying C/O regimes at the orbital radii of candidate protoplanets identified within these disks. When comparing these inferred disk C/O ratios with those measured for directly imaged exoplanets, we find a notable overlap and show that low C/O gas is common on tens of au scales in Herbig disks.

A near-infrared and optical study of NGC 5822: an open cluster hosting barium-stars and lithium-enriched giant stars

First Author: Holanda, N.
Instruments: FEROS
ProgramIDs: unknownID
BibCode: 2026MNRAS.546f2286H

We present a chemical abundance study of giant stars in the Galactic open cluster NGC 5822, which hosts two barium stars (#002 and #201) and three lithium-enriched giants (#006, #102, and #240). Using high-resolution optical and near-infrared (H and K band) spectra from FEROS and IGRINS, we determine atmospheric parameters and abundances for 23 elements (Li, C, N, O, F, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, Cr, Fe, Ni, Y, Ce, Nd, Yb, and Pb). This includes species not yet studied in this cluster, such as F, P, K, Yb, and Pb, as well as oxygen isotopic ratios

$^{16}$

$^{17}$

O and

$^{16}$

$^{18}$

O. Membership was assessed using astrometry and chemical abundances, providing insight into the evolutionary stages of Li-enriched giants and cluster parameters (age, distance, extinction). However, the identification of Ba-stars remains challenging due to their binary nature and less reliable astrometric solutions. The cluster's abundances are broadly consistent with expectations for the Galactic thin disc. The mean fluorine abundance agrees with chemical evolution models predicting that young clusters (<2 Gyr) exhibit elevated [F/Fe], with production from SN II, SN Ia, AGB, and Wolf─Rayet stars. No distinct chemical or rotational features were found to explain the lithium enrichment, likely occurring either during the red clump phase or near the RGB tip. For the Ba-stars, nucleosynthesis models combined with the cluster's turn-off mass suggest polluting companion masses of 3.00 and 3.75

${\rm M}_{\odot }$

for stars #002 and #201. These results highlight the importance of open clusters as laboratories for chemically peculiar stars.

A Search for Late-type Brown Dwarfs in the Euclid Quick Data Release 1

First Author: Kiwy, Frank
Instruments: VIRCAM
ProgramIDs: 179.A-2010, 179.A-2004
BibCode: 2026AJ....171..108K

We present the identification and characterization of 15 mid-to-late T dwarf candidates in the Euclid Quick Release 1 (Q1) data set, based on a combined photometric and spectroscopic analysis. Candidates were initially selected via color-based cuts in the Euclid Y_E − J_E and J_E − H_E color─color space, targeting the region occupied by ultracool dwarfs (UCDs) in synthetic photometry from the A. Sanghi et al. sample. From an initial pool of 38,845 sources, we extracted low-resolution near-infrared spectra from the Euclid Near-Infrared Spectrometer and Photometer instrument and applied a two-stage validation procedure that included spectral template fitting followed by visual inspection. Eight of the 15 validated candidates are newly identified objects with no prior literature association. We examined their morphological and photometric properties, and compared them with established spectral standards. Photometric distances were derived using band-averaged distance modulus estimates. We discuss the limitations and promise of the Euclid survey for UCD studies, and demonstrate the potential for discovering substellar populations beyond the reach of current wide-field surveys.

Astrometric and Spectroscopic Analysis of IC 2714: An Open Cluster Hosting a Lithium-rich Giant

First Author: Flaulhabe, T.
Instruments: FEROS
ProgramIDs: unknownID
BibCode: 2026ApJ...997..288F

Open clusters serve as laboratories to study and evaluate stellar evolution and Galactic chemical evolution models. Chemical peculiarities, such as lithium-rich giants, are rarely observed in these stellar systems. This work focuses on eight red giants (#005, #028, #034, #053, #087, #121, #126, and #190) previously reported as members of the Galactic cluster IC 2714. We conducted a detailed investigation using high-resolution spectroscopy, supplemented with data from the Gaia DR3 catalog. Besides deriving the cluster's fundamental parameters, we provide the most thorough chemical characterization of IC 2714 to date, reporting the abundance of 23 species, including light elements (Li, C, N, O), odd-Z elements (Na, Al), α-elements (Si, Ca, Ti, Mg), iron-peak elements (Sc, Cr, Ni), s-process-dominated elements (Y, Zr, Ba, La, Ce, Nd) and r-process elements (Sm, Eu). We also present the carbon isotopic ratios ¹²C/¹³C for the first time for seven stars. One particular star (#087) exhibits a high lithium abundance ( log∊ (Li)_NLTE = +1.54 dex) and a slightly higher projected rotational velocity ( vsini = 6.7 km s⁻¹). Our results suggest that the analyzed stars are in the core-helium-burning phase of evolution, where the most lithium-rich giants are found. Combining astrometric probabilities and chemical abundances, we conclude that two giants (#028 and #034) might not be cluster members.

Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES⁺ observations

First Author: Pelaez-Torres, A.
Instruments: CRIRES
ProgramIDs: 110.2492
BibCode: 2026A&A...705A.256P

Context. Transmission spectra of Neptune-sized exoplanets are frequently observed to be featureless at low-to-mid resolutions from space; whereas high-altitude clouds can mute spectral features, high atmospheric metallicities can also result in compressed envelopes, where low scale heights may also yield undetectable signatures. Aims. We aim to study the atmospheric properties of the warm Neptune GJ 436 b by combining a set of five transit events observed with the CARMENES spectrograph with one transit from CRIRES⁺ so as to provide the most constrained results possible at high resolution. Methods. We removed telluric and stellar signals from the data using SysRem and potential planetary signals were investigated using the cross-correlation technique. Following standard procedures for undetected species, we performed injection recovery tests and Bayesian retrievals to place constraints on the detectability of the main near-infrared absorbers. In addition, we simulated ELT/ANDES observations by computing end-to-end in silico datasets with EXoPLORE. Results. No molecular signals were detected in the atmosphere of GJ 436 b, which is consistent with previous studies. Combined CARMENES-CRIRES⁺ injection-recovery and Bayesian retrieval analyses show that the atmosphere is likely covered by high-altitude clouds (~1 mbar) at low and intermediate metallicities or, alternatively, is very metal-rich (≳ 900× solar), which would suppress spectral features without invoking clouds. Simulations of ELT/ANDES observations suggest a boost by nearly an order of magnitude to the upper limit in the photon-limited regime, reaching 0.1 mbar at 10-300× solar metallicities. Conclusions. The joint analysis of all useful transit observations from CARMENES and CRIRES⁺ provides the most stringent constraints to date on the atmospheric properties of GJ 436 b. Complementary CCF-based and retrieval approaches consistently indicate that the atmosphere is either cloudy or highly metal enriched. Any weak near-infrared absorption lines, if present, are likely to be below current detection limits. However, according to our simulations, these features may be revealed with ELT/ANDES even in single-transit observations.

Dissecting the dust distribution and polarization around two B213 young stellar objects with ALMA

First Author: Sato, Asako
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2021.1.01420.S, 2019.1.01209.S
BibCode: 2026A&A...706A.292S

Context. The pristine stages of disk formation during the protostellar phase and the processes of dust evolution in young disks remain largely unconstrained. Dust thermal emission at millimeter wavelengths and its polarization offer key insights into the physical processes and spatial distribution of material at the envelope-disk interface, as well as on early dust evolution around solar-type protostars. Aims. We characterize the dust properties and polarization mechanisms from envelope to disk scales in two young stellar objects (YSOs), IRAS 04166+2706 (K04166) and IRAS 04169+2702 (K04169) embedded in the same Taurus filament. We explore the nature of the dust polarization across scales and investigate their stage of evolution. Methods. We present deep (∼1.4 mm and ∼3 mm) polarimetric observations sampling the dust emission from 25 au to 3000 au using the Atacama Large Millimeter/submillimeter Array (ALMA). We modeled Stokes I emission to characterize disk and envelope contributions, while the polarization properties were analyzed to identify the dominant polarization mechanisms. Finally, in this work, we discuss the physical properties of both sources across scales. Results. K04166 shows extended Stokes I and polarized emission tracing a tentative hourglass magnetic field morphology in its envelope. In the inner envelope and disk (<100 au), the properties of the polarized emission change, suggesting the presence of a toroidal magnetic field around the disk or the presence of large grains in the inner envelope. K04169 exhibits compact Stokes I and polarized emission, consistent with self-scattering from the disk. Both disks are extremely compact, yet K04166 retains a substantial envelope while the one of K04169 is largely dissipated. Conclusions. Our multiscale ALMA polarimetric observations reveal a transition from magnetically aligned grains in envelopes to self-scattering in disks within the transition region of 20─50 au. These results provide important clues on dust grain growth and magnetic field morphology at the disk-envelope scales. The two sources, separated by <0.5 pc and embedded in a common filament, display striking differences, indicating that K04166 is a young embedded object with a substantial envelope threaded by relatively organized magnetic fields. Meanwhile, K04169 is more evolved, likely to be a young T-Tauri star. However, in both disks, the presence of large grains already suggest a scenario of early dust evolution in disks of the Class 0 stage.

Discovery of Multiple Ultra-broad-velocity Molecular Features Associated with the W44 Molecular Cloud

First Author: Makita, Momoko
Instruments: ALMA_Band_7
ProgramIDs: 2016.1.01548.S
BibCode: 2026ApJ...999L...3M

We report the discovery of multiple compact molecular features exhibiting extremely broad velocity widths toward the W44 molecular cloud. Atacama Large Millimeter/submillimeter Array CO J = 3─2 data reveal eight "Petit-Bullets" surrounding the previously known "Bullet." Each Petit-Bullet shows a distinct V-shaped structure in position─velocity space, reminiscent of the Y-shaped morphology of the Bullet, suggesting a common origin. These features are interpreted as the result of high-velocity plunges of compact gravitational objects into dense molecular gas. The spatial and kinematic properties of the Petit-Bullets suggest that the plunging material was not a single object but rather a small cluster of compact bodies. A virial mass of 1.0 × 10⁵ M_⊙ inferred from their velocity dispersion is comparable to that of typical globular clusters. Momentum analysis further implies that the main Bullet likely formed by an isolated black hole. These findings provide new evidence for dynamical interactions between halo clusters and disk molecular gas.

A Multiwavelength ALMA View of Gas and Dust in Binary Protoplanetary System AS 205: Evidence of Dust Asymmetric Distribution

First Author: Phuong, Nguyen Thi
Instruments: ALMA_Band_3, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2016.1.00484.L, 2018.1.01198.S, 2015.1.00168.S
BibCode: 2026ApJ...999...76P

We present Atacama Large Millimeter/submillimeter Array observations of multiwavelength dust emissions at 3.1 and 1.3 mm, along with molecular line emissions of CO(2─1), CO(3─2), ¹³CO(3─2), and C¹⁸O(3─2) at spatial resolutions of 7─45 au toward the protoplanetary system AS 205. The dust emissions exhibit two distinct components of AS 205 N and AS 205 S, separated by 1 .″ 3. While gas kinematics within the dust disk regions are dominated by Keplerian rotation, the more extended gas emission displays complex morphology and kinematics strongly affected by the binary gravitational interaction in the outer regions. The stellar masses of AS 205 N and AS 205 S are estimated at 0.78 ± 0.19 and 1.93 ± 0.86 M_⊙, respectively. Azimuthal variation is observed in the spectral index distribution of both disks. In AS 205 N, the spectral index minimum in the southwest is coincident with the peaks of CO(2─1), CO(3─2), and ¹³CO(3─2) integrated intensity and the relative position of its southern counterpart. On the other hand, the spectral index distribution in AS 205 S exhibits two prominent maxima, with the one in the northeast aligning with the peak of ¹³CO(3─2), and the peak in the south coinciding with local maxima in CO(2─1) and CO(3─2) azimuthal profiles. These results suggest a correlation between dust grain size and/or optical depth with the gas distributions. Dust trapping along the spiral arms possibly contributes to the spectral index minima in AS 205 N; however, the observed asymmetry across both disks suggests the involvement of additional mechanisms.

Cloud─Cloud Collisions Induce Filament-mediated Super Star Cluster Formation in the Antennae Overlap Region: Evidence from ALMA and JWST

First Author: Michiyama, Tomonari
Instruments: ALMA_Band_3
ProgramIDs: 2022.A.00032.S
BibCode: 2026ApJ...999..119M

The formation of super star clusters (SSCs) in galaxies remains a fundamental yet unresolved problem. Among the proposed mechanisms, cloud─cloud collisions (CCCs) have been suggested as a potential trigger, although observational validation has been limited. Here we present high-resolution ( 0.″12 , ∼14 pc) Atacama Large Millimeter/submillimeter Array observations of CO (J = 1─0) emission toward a super giant molecular cloud (SGMC) in the overlap region of the Antennae galaxies. The data resolve the SGMC into two distinct velocity components separated by ∼50 km s⁻¹. One component exhibits a "U"-shaped structure within a large filament likely shaped by ram pressure, while the other shows hub-filament morphology. Such a morphology is naturally interpreted as a CCC scenario. The 108 GHz continuum emission detected at the apparent collision interface is dominated by free─free radiation, with an ionizing photon rate consistent with the stellar mass and age of the optically identified SSCs. Supplementary infrared imaging with JWST reveals emission spatially coincident with the inferred collision interface, further supporting the CCC scenario. These results provide compelling, multiwavelength evidence that CCCs play a key role in triggering SSC formation in merging galaxies.

HOPS-288: A Laboratory for Complex Organics in Proto-binary/Proto-multiple Systems

First Author: Hsu, Shih-Ying
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00302.S, 2018.1.01038.S
BibCode: 2026ApJ...999...62H

Complex organic molecules (COMs) in young stellar objects have attracted significant attention in recent years due to their potential connection to prebiotic chemistry and their utility as tracers of warm or shocked gas components. Proto-binary and multiple systems with close separations are particularly valuable targets for investigating chemical inheritance and reaction, as their members are expected to form from similar material in their parental cloud. We present Atacama Large Millimeter/submillimeter Array observations of the hierarchical proto-triple system HOPS-288, focusing on the physical structure, kinematics, and COM compositions. The system is treated as a proto-binary system consisting of HOPS-288-A and HOPS-288-B due to the limited spatial resolutions, with a separation of 200 au. Three COM-rich features are revealed: two hot corinos associated with the two members, rich in a variety of COMs, and an intervening component between the two members traced by CH₃OH and tentatively by CH₃CHO. The hot corino in HOPS-288-A exhibits rotational features and might trace a disk. The hot corino in HOPS-288-B is also possibly exhibiting rotational motion. The intervening component could possibly trace a shocked region in the circumbinary disk or a bridge between the two members. The column densities of COMs, including ¹³CH₃OH, CH₂DOH, CH₃CHO, HCOOCH₃, C₂H₅OH, ¹³CH₃CN, and NH₂CHO, are broadly similar between the two sources, possibly suggesting the complex organic similarities among proto-binary/multiple systems. Given the complexity of the studied physical structures, further detailed investigations will be essential to confirm this result.

B-field Orion Protostellar Survey (BOPS). IV. The Relative Orientation between Magnetic Fields and Density Structures in Young Protostellar Envelopes

First Author: Cai, Kexin
Instruments: ALMA_Band_7
ProgramIDs: 2019.1.00086.S
BibCode: 2026ApJ...999..126C

We investigate the relative alignment between density structures and magnetic fields in eight young protostars from the Atacama Large Millimeter/submillimeter Array B-field Orion Protostellar Survey. Column density maps are derived from 870 μm dust continuum emission, and the Histogram of Relative Orientations method is applied to quantify the correlation between magnetic field orientations and density structures on envelope scales (∼10³ au). We find that the relative alignment shows overall little evidence of systematic evolution with column density, suggesting that column density alone does not fully determine the alignment. The magnetization level also plays a crucial role, with weakly magnetized envelopes exhibiting predominantly parallel or random alignment, whereas strongly magnetized ones show perpendicular configurations even at moderate densities. These results reveal that density and magnetization jointly shape the morphology of protostellar envelopes and the coupling between gravity and magnetic fields during early stages of star formation.

The Extended Mapping Obscuration to Reionization with ALMA (Ex-MORA) Survey: 5σ Source Catalog and Redshift Distribution

First Author: Long, Arianna S.
Instruments: ALMA_Band_3, ALMA_Band_4
ProgramIDs: 2021.1.00246.S, 2021.1.00225.S, 2019.1.01600.S
BibCode: 2026ApJ...999...47L

One of the greatest challenges in galaxy evolution over the last decade has been constraining the prevalence of heavily dust-obscured galaxies in the early Universe. At z > 3, these galaxies are increasingly rare, and difficult to identify, as they are interspersed among the more numerous dust-obscured galaxy population at z = 1─3, making efforts to secure confident spectroscopic redshifts expensive, and sometimes unsuccessful. In this work, we present the Extended Mapping Obscuration to Reionization with the Atacama Large Millimeter/submillimeter Array (ALMA; Ex-MORA) Survey—a 2 mm blank-field survey in the COSMOS-Web field, and the largest ever ALMA blank-field survey to date, covering 577 arcmin². Ex-MORA is an expansion of the MORA survey designed to identify primarily z > 3 dusty, star-forming galaxies while simultaneously filtering out the more numerous z < 3 population by leveraging the very negative K-correction at observed-frame 2 mm. We identify 37 significant (>5σ) sources, 33 of which are robust thermal dust emitters. We measure a median redshift of <z>=3.8−1.52+1.7 , with two-thirds of the sample at z > 3, and just under half at z > 4, demonstrating the overall success of the 2 mm selection technique. The total integrated z > 3 volume density of Ex-MORA sources is ∼1─3 × 10⁻⁵ Mpc⁻³, consistent with other surveys of infrared luminous galaxies at similar epochs. We also find that techniques using rest-frame optical emission (or lack thereof) to identify z > 3 heavily dust-obscured galaxies miss at least half of Ex-MORA galaxies. This supports the idea that the dusty galaxy population is heterogeneous, and that synergies across observatories spanning multiple energy regimes are critical to understanding their formation and evolution at z > 3.

Digging into the Interior of Hot Cores with ALMA (DIHCA). VII. Disk Candidates around High-mass Stars and Evidence of Anisotropic Infall

First Author: Olguin, Fernando A.
Instruments: ALMA_Band_6
ProgramIDs: 2016.1.01036.S, 2017.1.00237.S
BibCode: 2026ApJ...999..106O

We study the kinematics of condensations in 30 fields forming high-mass stars with the Atacama Large Millimeter/submillimeter Array at a high resolution of ∼0.″08 on average (∼230 au). The presence of disks is important for feeding high-mass stars without feedback halting growth as their masses increase. In the search for velocity gradients resembling rotation that can reveal the presence of disks, we analyze the emission of gas tracers in 49 objects using CH₃OH, CH₃CN, and tentative detections of HNCO and cis-HCOOH. Most of the velocity distributions show velocity gradients indicative of rotation. We reveal a total of 32 disk candidates, the largest sample to date that has been uniformly analyzed at a few hundred astronomical unit scales in the high-mass regime. Their position─velocity maps are generally asymmetric with one side brighter than the opposite. We successfully fit a power law to the position─velocity maps of the disk candidates and find indices between −0.5 (Keplerian rotation) and −1 (rotation under specific angular momentum conservation) with a median of −0.7. Under Keplerian rotation assumption, we estimate central masses, uncorrected for inclination, ranging between 7 and 45 M_⊙. Excluding outliers, the disk candidates are relatively more compact (<200 au) and less massive (<5 M_⊙) than previous results at coarser angular resolution. We calculate an average Toomre-Q parameter and find that most are gravitationally unstable (median of 0.5). We conclude that these observations offer the first opportunity to separate the disk and envelope components of hot cores on a statistically significant sample, and confirm that anisotropic collapse plays a role in feeding high-mass (proto)stars.

Constraining Properties of Dust Formed in Wolf─Rayet Binary WR 112 Using Mid-infrared and Millimeter Observations

First Author: Wu, Donglin
Instruments: ALMA_Band_6
ProgramIDs: 2023.1.00999.S, 2024.1.00803.S
BibCode: 2026ApJ...999...32W

Binaries that host a carbon-rich Wolf─Rayet (WC) star and an OB-type companion can be copious dust producers. Yet the properties of dust, particularly the grain size distribution, in these systems remain uncertain. We present Band 6 observations of WR 112 by the Atacama Large Millimeter/submillimeter Array telescope (ALMA), which are the first millimeter observations of a WC binary system capable of resolving its dust emission. By combining ALMA observations with James Webb Space Telescope images, we were able to analyze the spatially resolved spectral energy distribution (SED) of WR 112. We found that the SEDs are consistent with emissions from hydrogen-poor amorphous carbon grains. Notably, our results also suggest that the majority of grains in the system have radii below one micrometer, and the extended dust structures are dominated by nanometer-sized grains. Among four parameterizations of the grain radius distribution that we tested, a bimodal distribution, with abundant nanometer-sized grains and a secondary population of 0.1 μm grains, best reproduces the observed SED. This bimodal distribution helps to reconcile the previously conflicting grain size estimates reported for WR 112 and for other WC systems. We hypothesize that dust destruction mechanisms such as radiative torque disruption and radiative-driven sublimation are responsible for driving the system to the bimodal grain size distribution.

Early Planet Formation in Embedded Disks (eDisk). XIX. Structures of Molecular Outflows

First Author: Feeney-Johansson, Anton
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00261.L, 2019.A.00034.S, 2015.1.01512.S
BibCode: 2026AJ....171..172F

As part of the ALMA Large Program "Early Planet Formation in Embedded Disks," ¹²CO (2─1) was observed towards 19 nearby low-mass protostars. Of these objects, 15 sources are found to show molecular outflow emission. Based on their morphological and kinematical structures, the CO outflows are classified into three types: a wind-driven shell, where ambient material is swept up by a wide-angle wind from the star, a bow shock, and a slow disk wind, which is a conical or parabolic flow with onion-like velocity structure. We categorize 11 outflows as a slow disk wind, 7 as a wind-driven shell, and 1 as a bow shock. Four of these outflows were found to show signs of both slow disk wind and wind-driven shell characteristics. Five objects show misalignment between the red- and blueshifted outflows. Seven objects show significant misalignment between the outflow axis (either or both of the red- and blueshifted outflows) and the minor axis of the dust continuum emission around the protostar. For the objects showing wind-driven shell emission, we compare simple parametrized models with the observations to derive physical properties of the observed shells, such as their dynamical ages. This shows evidence of a time variability in the outflows, such as changes in their direction. In some objects, large differences are seen between the properties of the red- and blueshifted outflows, possibly indicating differences in the properties of the ambient medium with which the outflow interacts.

Silicon monoxide in the filamentary infrared dark cloud G035.39-00.33: An ALMA view

First Author: Liu, Rong
Instruments: ALMA_Band_3
ProgramIDs: 2016.1.01363.S
BibCode: 2026A&A...706A.328L

Aims. Filamentary infrared dark clouds (IRDCs) are believed to represent the initial conditions for massive star and cluster formation. Methods. We investigated the IRDC G035.39-00.33 using SiO, H¹³CO⁺, CH₃OH, and CS emission observed with ALMA at 3.5″ resolution (∼0.05 pc). The analysis of the SiO emission provides a record of shock activity within the cloud, offering insights into both the current level of star formation and the cloud's formation mechanisms. Results. We identify several regions with broad SiO emission clearly associated with outflows, pinpointing the locations of ongoing star formation across the cloud. The ALMA images also reveal a series of spatially extended SiO emission spots with narrow line profiles aligned along an arc-like path that is also seen in CS and CH₃OH emission. While the broad SiO emission is mainly associated with the main cloud filament, as seen in visual extinction, the narrow SiO arch is located at the edge of the cloud, far from the identified sites of star formation activity. The presence of these arc-like morphologies suggests that large-scale shocks may have compressed the gas in the surroundings of the G035.39-00.33 cloud, shaping its filamentary structure. By inspecting the large-scale radio continuum emission around G035.39-00.33, we find that this IRDC is part of a larger star-forming complex where the densest and coolest material appears at the interacting regions between a supernova remnant (SNR) and an expanding HII region. In particular, we hypothesise that this IRDC may be spatially coincident with the ionised expanding gas associated with the previously identified SNR G35.6-0.4. Conclusions. We suggest that collisions between giant molecular clouds and expanding gas flows from interacting SNRs and HII regions may be responsible for the observed arc-like structures. Such shock compressions could play an important role in the formation of IRDCs and in the potential triggering of star formation.

The Cosmic Owl: Twin Active Collisional Ring Galaxies with Starburst Merging Front at z = 1.14

First Author: Li, Mingyu
Instruments: ALMA_Band_6
ProgramIDs: 2016.1.01040.S
BibCode: 2026ApJ...999...40L

Galaxy mergers play a critical role in driving galaxy evolution, especially by transforming galaxy morphology, redistributing gas around galaxies, triggering active galactic nuclei (AGN), and stimulating star formation. We present the Cosmic Owl, a galaxy merger at z = 1.14, identified in the COSMOS field. Deep imaging and spectroscopy from JWST, the Atacama Large Millimeter/submillimeter Array, and the Very Large Array reveal a complex system of twin collisional ring galaxies, exhibiting nearly identical morphologies. The grism spectra from the JWST COSMOS-3D program confirm that both galaxies host an AGN. A bipolar radio jet from one AGN extends to strike the merging front. In addition, we detect a starburst at the merging front, characterized by luminous extended nebular line emission and a massive cold gas reservoir. This starburst is likely triggered by interstellar shocks induced by galaxy collision and the AGN jet. The twin ring structure of the Cosmic Owl requires further numerical simulations to clarify the precise conditions that lead to the formation of this rare morphology. This system exemplifies how shock-induced star formation, driven by galaxy collision or AGN jet, can act as a crucial mechanism for triggering intense starbursts in the early Universe.

Interaction of the central jet with the surrounding gas in the protostellar outflow from IRAS 04166+2706

First Author: Tafalla, M.
Instruments: ALMA_Band_6
ProgramIDs: 2021.1.00575.S
BibCode: 2026A&A...706A.248T

Context. The outflow from the Class 0 protostar IRAS 04166+2706 (hereafter IRAS 04166) contains a remarkably symmetric jet-like component of extremely high-velocity (EHV) gas. Aims. We studied the IRAS 04166 outflow and investigated the relation between its EHV component and the slower outflow gas. Methods. We mosaicked the CO(2─1) emission from the IRAS 04166 outflow using the 12m and the Compact Arrays of ALMA. We also developed a ballistic toy model of the gas ejected laterally from a jet to interpret the data. Results. In agreement with previous observations, the ALMA data show that the slow outflow component is distributed in two opposed conical lobes and has a shear-flow pattern with velocity increasing toward the axis. The EHV gas consists of a series of arc-like condensations that span the full width of the conical lobes and merge with their walls, suggesting that the fast and slow outflow components are physically connected. In addition, position─velocity diagrams along the outflow axis show finger-like extensions that connect the EHV emission with the origin of the diagram, as if part of the EHV gas had been decelerated by its interaction with the low-velocity outflow. A ballistic model can reproduce these finger-like extensions assuming that the EHV gas consists of jet material that has been ejected laterally over a short period of time and has transferred part of its momentum to the surrounding shear flow. Conclusions. The EHV gas in the IRAS 04166 outflow seems to play a role in the acceleration of the slower gas component. The presence of similar finger-like extensions in the position─velocity diagrams of other outflows suggests that this process may be occurring in other systems, even if the EHV component is not seen because it has an atomic composition.

Evidence of Gas Depletion in Quasars with Moderate Radio Emission

First Author: Wen, Yuhan
Instruments: ALMA_Band_7
ProgramIDs: 2016.2.00060.S, 2022.1.00029.S
BibCode: 2026ApJ...998..323W

The energy released by active galactic nuclei (AGNs) is considered to have a profound impact on the cold gas properties of their host galaxies, potentially heating or removing the gas and further suppressing star formation. To understand the feedback from AGN radio activity, we investigate its impacts on the cold gas reservoirs in AGNs with different radio activity levels. We construct a quasar sample with a mean z ∼ 1.5 and a mean L_bol ∼ 10^45.8 erg s⁻¹, all with Herschel detections to enable estimates of the total gas mass through the galactic dust continuum emission. The sample is then crossmatched with radio catalogs and divided into radio-loud quasars, radio-detected radio-quiet (RQ) quasars, and radio-undetected quasars based on their radio loudness. Through spectral energy distribution fitting, we find the radio-detected RQ quasars exhibit evidence of gas deficiency with host galaxies possessing ∼0.3 dex lower dust and gas masses compared to the other two groups, despite being matched in M_BH, L_bol, M_*, and star formation rate. Furthermore, evidence from optical spectra shows that both the fraction and velocity of outflows are higher in the radio-detected RQ group, suggesting a connection between the ionized gas outflows and the moderate radio activity. These results suggest that the AGN feedback could be more efficient in AGNs with weak/moderate radio emission than in those without radio detection or those with strong radio emission. Further high-resolution observations are needed to understand the interaction between the interstellar medium and the weak/moderate AGN radio activity.

ALMA Polarization Study of the Magnetic Fields in Two Massive Clumps in the 20 km s⁻¹ Cloud of the Central Molecular Zone

First Author: Liu, Yuhua
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.00286.S
BibCode: 2026ApJ...998..330L

We present the Atacama Large Millimeter/submillimeter Array observations of linearly polarized 870 μm continuum emission at ∼0 .″ 2 (2000 au) resolutions toward the two massive clumps, Clump 1 and Clump 4, in the 20 km s⁻¹ cloud. The derived magnetic field strength for both clumps ranges from ∼0.3 to 3.1 mG using the angular dispersion function method. The magnetic field orientations across multiple scales suggest that the magnetic field dominates at the cloud scale, whereas gravity appears to govern structures at the core (0.01−0.1 pc) and condensation (≤0.01 pc) scales. Furthermore, the study on the angular difference between the orientations of the local gravity gradient and the magnetic field suggests that the magnetic field predominantly governs the dynamics in the diffuse regions, while gravity and star formation feedback become increasingly significant within the dense regions. The ratio of the magnetic field tension force F_B to the gravitational force F_G suggests that the magnetic field may provide some support against gravity, but it is insufficient to prevent gas from infalling toward the dense cores.

ALMAGAL. VII. Cataloging Hierarchical Continuum Structure from Cores to Clumps across the Galactic Disk

First Author: Wallace, Jennifer
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00195.L
BibCode: 2026ApJ...998..302W

Investigating the multiscale fragmentation of dense clumps into compact cores is essential for understanding the processes that govern the initial distribution of mass in stellar clusters and how high-mass stars (>8 M_⊙) form. We present a catalog of the hierarchical continuum structure from 904 clumps observed in the ALMAGAL program, a high-resolution (0 .″ 15─0 .″ 8) 1.38 mm Atacama Large Millimeter/submillimeter Array large program targeting dense clumps capable of high-mass star formation throughout the Galactic disk. We use astrodendro, a dendrogram-based algorithm, on a uniform linear resolution (2000 au) version of the data to extract 5160 continuum structures with effective radii spanning 800─42000 au and estimated masses between 0.05─670 M_⊙. With our large sample, we statistically examine differences in clump properties for regions with varying levels of hierarchical complexity. We find that clumps exhibiting the richest hierarchical morphology have distributions with higher dust temperatures, surface densities, luminosity-to-mass (L/M) ratios, and most massive core masses, indicating that these regions tend to be at later evolutionary stages. We find a positive correlation between the mass of cores from the ALMAGAL core catalog and the surface density of their surrounding structures identified in this work. However, this correlation is weaker for cores in more evolved clumps, where lower-mass cores can be found at higher local surface densities. This could indicate that some cores accrete mass less efficiently from the intraclump reservoir than others, despite the total available mass increasing over time, a scenario that is congruent with a clump-fed core accretion model.

Characterizing the physical and chemical properties of the Class I protostellar system Oph-IRS 44: Binarity, infalling streamers, and accretion shocks

First Author: Artur de la Villarmois, E.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2022.1.00209.S, 2019.1.01792.S
BibCode: 2026A&A...706A.256A

Context. In the low-mass star formation process, theoretical models predict that material from the infalling envelope could be shocked as it encounters the outer regions of the disk. This is followed by an increase in the dust temperature and sublimation, into the gas phase, of molecular species that will otherwise remain locked on dust grains. Although accretion shocks are predicted by theoretical models, only a few protostars show evidence of these shocks at the disk-envelope interface, and the main formation path of shocked-related species is still unclear. They can be formed entirely on dust surfaces and then sublimated, or through reactions in the gas phase, or a combination of both. Aims. The goal of this work is to assess the chemistry associated with accretion shocks and the formation path of molecules that are usually associated with these dense and warm regions. Methods. We present new observations of IRS 44, a Class I source with a resolved disk that has previously been associated with accretion shocks, taken at high angular resolution (0_⋅^''1, corresponding to 14 au) with the Atacama Large Millimeter/submillimeter Array (ALMA). We observe three different spectral settings in bands 6 and 7, targeting multiple molecular transitions of CO, H₂CO, and simple sulfur-bearing species (such as CS, SO, SO₂, H₂S, OCS, and H₂CS). Results. In continuum emission, the binary nature of IRS 44 is observed for the first time at sub-millimeter wavelengths and the emission agrees with the optical and infrared counterparts. Infalling signatures are seen for the CO 2─1 line and the emission peaks at the edges of the continuum emission around IRS 44 B, the same region where bright SO and SO₂ emission is seen. Weak CS and H₂CO emission is observed, while OCS, H₂S, and H₂CS transitions are not detected. Conclusions. IRS 44 B seems to be more embedded than IRS 44 A, indicating a non-coeval formation scenario or the rejuvenation of source B due to late infall. CO 2─1 emission is tracing the outflow component at large scales, infalling envelope material at intermediate scales, and two infalling streamer candidates are identified at disk scales. Infalling streamers might produce accretion shocks when they encounter the outer regions of the infalling-rotating envelope. These shocks heat the dust and efficiently release S-bearing species (such as H₂S, SO, and SO₂), as well as promoting a lukewarm chemistry (~200 K) in the gas phase. With the majority of carbon locked in CO, there is little free C available to form CS and H₂CS in the gas, leaving an oxygen-rich environment. The high column densities of SO and SO₂ might therefore be a consequence of two processes: direct thermal desorption from dust grains and gas-phase formation due to the availability of O and S. IRS 44 is an ideal candidate with which to study the chemical consequences of accretion shocks and the dynamical connections between the envelope and the disk, through infalling streamers.

δ Circini: A massive hierarchical triple system with an eclipsing binary

First Author: Svrckova, J.
Instruments: FEROS, GRAVITY, HARPS, PIONIER
ProgramIDs: 089.C-0211, 189.C-0644, 093.C-0503, 098.D-0706, 099.D-0777, 596.D-0495, 5100.D-0721, 182.D-0356, 185.D-0056, 178.D-0361, 109.23HT
BibCode: 2026A&A...705A..99S

δ Circini is known to be a massive multiple system containing a 3.9 d inner eclipsing binary in a slightly elliptical orbit exhibiting slow apsidal motion and a distant tertiary with a probable period of 1644 d. All three components of the system are O- or B-type stars. We carried out a comprehensive study of the system, based on light curves from TESS and other instruments, a new series of echelle spectra, older spectra from the ESO archive, and several VLTI interferometric observations. Due to the large amount of different types of data covering both orbits in the system, we obtained a more precise value of the long orbital period (1603.24 ± 0.19 d) and fully determined all other orbital parameters. Although both orbits are eccentric, their period ratio is large enough for the system to be dynamically stable. The inner and outer orbits are in the same plane, which means that no Kozai-Lidov mechanism is acting in the system. Assuming solar metallicity in our MESA models, we found ages of (4.4 ± 0.1), (4.7 ± 0.2), and (3.8 ± 1.3) Myr for the primary, the secondary, and the tertiary, respectively. Our evolutionary scenario predicts that the inner eclipsing binary will merge within approximately 1.7 Myr and eventually evolve into a black hole. The distance to the system, estimated from the angular size of the outer orbit is (809.9 ± 1.8) pc, which implies that δ Cir might be located close to the centre of a stellar population ASCC 79, a subgroup of the young Circinus complex. With a total mass of (53.04 ± 0.29) M_⊙, δ Cir can contribute a significant fraction of the total mass of the population.

On the dusty proximate damped Lyman-α system toward Q 2310−3358 at z = 2.40

First Author: Han, S.
Instruments: XSHOOTER
ProgramIDs: 113.268S
BibCode: 2026A&A...705A.123H

Quasar absorption systems not only affect the way quasars are selected, but also serve as key probes of galaxies, providing insight into their chemical evolution and interstellar medium (ISM). Recently, a method based on Gaia astrometric measurements has aided the selection of quasars reddened by dust hitherto overlooked. We conducted a spectroscopic study using VLT/X-Shooter on one such dust-reddened quasar, Q 2310─3358. This quasar, at z = 2.3909 ± 0.0022, is associated with a damped Lyman-α absorber (DLA) at nearly the same redshift 2.4007 ± 0.0003, with a neutral hydrogen column density of log N(H I) = 21.214 ± 0.003. The DLA is very metal-rich (close to solar metallicity after correction for depletion on dust grains). Its properties align with the metal-to-dust ratio and the mass-metallicity relation established in previous large samples of DLAs. Surprisingly, given its proximity to the quasar in redshift, the absorber has strong cold gas characteristics, including C I and H₂. Based on the derived kinetic temperature of 71₋₁₅⁺²⁸ 71 − 15 + 28 K, we infer the presence of a strong UV radiation field, which in turn suggests that the quasar and the DLA are in close proximity, i.e., part of the same galaxy and not just different objects in the same overdensity of galaxies. We used the line ratios of the C I fine-structure lines to constrain the density of the cold gas, yielding n_H ∼ 10³ cm⁻³. Our analysis extends the understanding of z_abs ≍ z_em absorption line systems and provides valuable constraints on the interplay between dust, metals, and neutral gas in the ISM of early galaxies.

Extreme Neutral Outflow in a Non-active Galactic Nucleus Quiescent Galaxy at z ∼ 1.3

First Author: Sun, Yang
Instruments: MUSE
ProgramIDs: 1101.A-0127, 096.A-0045, 095.A-0010, 094.A-0289
BibCode: 2026ApJ...997..140S

We report the discovery of a substantial sodium doublet (Na D λλ5890, 5896)—traced neutral outflow in the quiescent galaxy JADES-GS-206183 at z = 1.317. Its JWST/NIRSpec-Microshutter Array spectrum shows a deep, blueshifted Na D absorption, revealing a neutral outflow with vout=828−49+79kms−1 and a mass outflow rate of log(Ṁout/M⊙yr−1)=2.40−0.16+0.11 . This outflow rate exceeds that of any neutral outflows identified beyond z ∼ 1 by the same line and is comparable with those in local galaxies with intensive star formation (SF) or luminous active galactic nuclei (AGN). JADES-GS-206183 is also a peculiar quiescent galaxy with a spiral+bar morphology, high dust attenuation (A_V = 2.27 ± 0.23 mag). Paschen α (Paα) emission from the FRESCO NIRCam grism confirms its low star formation rate (SFR_Paα = 10.78 ± 0.55 M_⊙ yr⁻¹), placing it 0.5 dex below the main sequence ( log(sSFRyr−1)=−10.2 ). Despite the systematics introduced by different SF history priors, the spectral energy distribution modeling, combining Hubble Space Telescope-to-NIRCam photometry with the Very Large Telescope/MUSE spectrum, suggests that JADES-GS-206183 experienced an older episode of SF 0.5─2 Gyr ago and a possible rejuvenation within the recent ∼10 Myr. Moreover, rest-frame optical lines indicate that the current AGN activity of JADES-GS-206183, if present, is also weak. Even though we tentatively detect a broad component of the Hα line, it likely traces an ionized outflow rather than an AGN. The results demonstrate that the Na D outflow in JADES-GS-206183 is highly unlikely to be driven by current SF or nuclear activity. Instead, it may represent a long-lasting fossil outflow from past AGN activity, potentially cotriggered with the early phase of rejuvenation.

The Galaxy Activity, Torus, and Outflow Survey (GATOS): X. Molecular gas clumpiness under the influence of AGN

First Author: Esposito, Federico
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.00082.S, 2018.1.00113.S
BibCode: 2026A&A...705A..33E

The distribution of molecular gas on small scales regulates star formation and the growth of supermassive black holes in galaxy centers. Yet, the role of active galactic nuclei (AGN) feedback in shaping this distribution remains poorly constrained. We investigate how AGNs influence the small-scale structure of molecular gas in galaxy centers by measuring the clumpiness of CO(3 − 2) emission observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in the nuclear regions (50 − 200 pc from the AGNs) of 16 nearby Seyfert galaxies from the Galaxy Activity, Torus, and Outflow Survey (GATOS). To quantify clumpiness we applied three different methods: (1) the median of the pixel-by-pixel contrast between the original and smoothed maps; (2) the ratio of the total excess flux to the total flux, after subtracting the background smoothed emission; and (3) the fraction of total flux coming from clumpy regions, interpreted as the mass fraction in clumps. We find a negative correlation between molecular gas clumpiness and AGN X-ray luminosity (L_X), suggesting that higher AGN activity is associated with smoother gas distributions. All methods reveal a turnover in this relation around L_X = 10⁴² erg s⁻¹, possibly indicating a threshold above which AGN feedback becomes efficient at dispersing dense molecular structures and suppressing future star formation. Our findings provide new observational evidence that AGN feedback can smooth out dense gas structures in galaxy centers.

Probing jet base emission of M87* with the 2021 Event Horizon Telescope observations

First Author: Saurabh
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00841.V, 2019.1.01797.V
BibCode: 2026A&A...706A..27S

We investigate the presence and spatial characteristics of the jet base emission in M87* at 230 GHz, enabled by the significantly enhanced (u,v) coverage in the 2021 Event Horizon Telescope (EHT) observations. The integration of the 12−m Kitt Peak Telescope (USA) and NOEMA (France) stations into the array introduces two critical intermediate-length baselines to SMT (USA) and IRAM 30−m (Spain), providing sensitivity to emission structures at spatial scales of ∼250 μas and ∼2500 μas (∼ 0.02 pc and ∼ 0.02 pc). Without these new baselines, previous EHT observations of the source in 2017 and 2018 lacked the capability to constrain emission on large scales, where a "missing flux" of order ∼1 Jy is expected to reside. To probe these scales, we analyzed closure phases─robust against station-based gain calibration errors─and model the jet base emission using a simple Gaussian component offset from the compact ring emission at spatial separations > 100 μas. Our analysis revealed a Gaussian feature centered at (∆RA ≍ 320 μas, ∆Dec. ≍ 60 μ as), projected separation of ≍ 5500 AU, with an estimated flux density of only ∼60 mJy, implying that most of the missing flux identified in previous EHT studies had to originate from different, larger scales. Brighter emission at the relevant spatial scales is firmly ruled out, and the data do not favor more complex models. This component aligns with the inferred position of the large-scale jet and is therefore physically consistent with the emission of the jet base. While our findings point to detectable jet base emission at 230 GHz, the limited coverage provided by only two intermediate baselines limits our ability to robustly reconstruct its morphology. Consequently, we treated the recovered Gaussian as an upper limit on the jet base flux density. Future EHT observations with expanded intermediate baseline coverage will be essential to constrain the structure and nature of this component with higher precision.

ALMA and JWST Imaging of z > 6 Quasars: No Spatial Position Offset Observed between Quasars and Their Host Galaxies

First Author: Wilde, Aurora
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00908.S, 2018.1.01188.S, 2019.1.00672.S, 2019.1.01025.S, 2021.1.00934.S
BibCode: 2026ApJ...996....8W

We present a study determining the spatial offset between the position of the supermassive black hole (as traced through their broad line regions) and the host galaxy in six z > 6 quasars. We determined the host galaxy's position from ≲ 0.″10 (≲600 pc) resolution Atacama Large Millimeter/submillimeter Array (ALMA) [C II] 158 μm and corresponding dust continuum imaging. We determined the quasar's position from ≲400 pc resolution James Webb Space Telescope Near-Infrared Camera (JWST NIRCam) imaging. We estimated the observational uncertainties on the quasar's position using astrometric data from the Global Astrometric Interferometer for Astrophysics of field stars within the NIRCam images. We find that all six quasars are found within the central ∼400 pc of their host galaxy dust continuum and [C II] emission. Apparent offsets seen in rest-frame optical JWST observations are not detected in our ALMA data, suggesting they likely result from dust obscuration rather than a true physical separation between the SMBH and its host galaxy. Kinematic modeling of these data further reveals that none of the galaxies show evidence for recent merger activity, and most of the galaxies can be accurately modeled using a simple disk model. The lack of an offset supports theoretical models that predict that positional offset within these galaxies is either short-lived or intrinsically rare.

Benchmarking Dimensionality Reduction Methods for High-dimensional ALMA Image Cubes

First Author: Scolati, Haley N.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2015.1.00657.S, 2018.1.00047.S, 2019.1.00246.S, 2019.1.00507.S, 2019.1.00558.S
BibCode: 2026AJ....171...87S

High-dimensional astronomical data cubes provide a wealth of spectral and structural information that can be used to study astrophysical and chemical processes. The complexity and sheer size of these datasets pose significant challenges in their efficient analysis, visualization, and interpretation. In specific astronomical use cases, a number of dimensionality reduction techniques, including traditional linear (e.g., principal component analysis) and modern nonlinear methods (e.g., convolutional autoencoders) have been used to tackle this high-dimensional problem. In this study, we assess the strengths, weaknesses, and nuances of various methods in their ability to capture and preserve astronomically relevant features at lower dimensions. We provide recommendations to guide users in identifying and incorporating these treatments to their data, and provide insights into the computational scalability of these methods for observatory-level data processing. This benchmark study uses publicly available archival Atacama Large Millimeter/submillimeter Array (ALMA) data from a diverse sampling of source morphologies and observing setups to assess the performance and trade-offs between computational cost, image reconstruction accuracy, and scalability. Finally, we discuss the generalizability of these techniques in regard to data segmentation and labeling algorithms, and how they can be exploited for advanced data product generation and streamlined archival analysis as we prepare to enter the era of the ALMA Wideband Sensitivity Upgrade.

QHSC: The Quasar Candidate Catalog for the Hyper Suprime-Cam Subaru Strategic Program

First Author: Zhu, Rui
Instruments: VIMOS, VIRCAM
ProgramIDs: 070.A-9007, 072.A-0586, 073.A-0647, 177.A-0837, 175.A-0839, 179.A-2006, 179.A-2005, 179.A-2004, 179.A-2010
BibCode: 2026ApJS..282...38Z

The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a deep wide-field multiband imaging survey consisting of three layers (Wide, Deep, and UltraDeep), with the Wide layer covering ∼1470 deg² to a depth of i ∼ 26 mag. We present the QHSC catalog, a machine learning─selected sample of quasar candidates with photometric redshifts in the Wide layer of the HSC-SSP survey (Public Data Release 3). The full QHSC catalog contains four distinct samples: a Master Sample with HSC-only photometry, an HSC+WISE sample, and two samples including near-infrared data from UKIDSS and VISTA surveys, denoted as GoldenU and GoldenV. For each sample, an XGBoost classifier is trained and evaluated using independent spectroscopic test sets from HETDEX, VVDS, and zCOSMOS-bright. The numbers of quasar candidates in the QHSC catalog are 1,184,574 (Master), 371,777 (HSC+WISE), 87,460 (GoldenU), and 120,572 (GoldenV), with respective completeness values of 85.3%, 92.7%, 89.8%, and 91.3%. We develop ensemble photometric redshift estimators based on bootstrap aggregating (bagging) of multiple XGBoost regressors, achieving outlier fractions of 21.7%, 13.1%, 9.5%, and 10.7% for these samples. The catalog provides quasar classification probabilities (p_QSO), enabling construction of purer subsamples via thresholding. This work offers a valuable resource for studies of quasars and cosmology, and highlights the effectiveness of machine learning for quasar selection in future wide and deep imaging surveys. The catalog is publicly available at doi:10.5281/zenodo.17515028.

COSMOS2025: The COSMOS-Web galaxy catalog of photometry, morphology, redshifts, and physical parameters from JWST, HST, and ground-based imaging

First Author: Shuntov, Marko
Instruments: VIRCAM
ProgramIDs: 179.A-2005, 198.A-2003, 110.25A2, 1104.A-0643, 284.A-5026
BibCode: 2025A&A...704A.339S

We present COSMOS2025, the COSMOS-Web catalog of photometry, morphology, photometric redshifts, and physical parameters for more than 700 000 galaxies in the Cosmic Evolution Survey (COSMOS) field. This catalog is based on our James Webb Space Telescope 255 h COSMOS-Web program, which provides deep near-infrared imaging in four NIRCam (F115W, F150W, F277W, F444W) and one MIRI (F770W) filter over the central ~0.54 deg² (~0.2 deg² for MIRI) in COSMOS. These data are combined with ground- and space-based data to derive photometric measurements of NIRCam-detected sources using both fixed-aperture photometry (on the space-based bands) and a profile-fitting technique on all 37 bands spanning 0.3 μm to 8 μm. We provide morphology for all sources from complementary techniques including profile fitting and machine-learning classification. We derive photometric redshifts, physical parameters, and non-parametric star formation histories from spectral energy distribution (SED) fitting. The catalog has been extensively validated against previous COSMOS catalogs and other surveys. Photometric redshift accuracy measured using spectroscopically confirmed galaxies out to z ~ 9 reaches σ_MAD = 0.012 at m_F444W < 28 and remains at σ_MAD ≲ 0.03 as a function of magnitude, color, and galaxy type. This represents a factor of ~2 improvement at 26 AB mag compared to COSMOS2020. The catalog is approximately 80% complete at log(M_⋆/M_⊙) ~ 9 at z ~ 10 and at log(M_⋆/M_⊙) ~ 7 at z ~ 0.2, representing a gain of 1 dex compared to COSMOS2020. COSMOS2025 represents the definitive COSMOS-Web catalog. It is provided with complete documentation, together with redshift probability distributions, and it is ready for scientific exploitation today.

exoALMA. XIX. Confirmation of Non-thermal Line Broadening in the DM Tau Protoplanetary Disk

First Author: Hardiman, Caitlyn
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.01123.L
BibCode: 2026ApJ...997L..47H

Turbulence is expected to transport angular momentum and drive mass accretion in protoplanetary disks. One way to directly measure turbulent motion in disks is through molecular line broadening. DM Tau is one of only a few disks with claimed detection of nonthermal line broadening of 0.25c_s─0.33c_s, where c_s is the sound speed. Using the radiative transfer code MCFOST within a Bayesian inference framework that evaluates over five million disk models to efficiently sample the parameter space, we fit high-resolution ( 0.″15 , 28 m s⁻¹) ¹²CO J = 3─2 observations of DM Tau from the exoALMA Large Program. This approach enables us to simultaneously constrain the disk structure and kinematics, revealing a significant nonthermal contribution to the line width of ∼0.4c_s, inconsistent with purely thermal motions. Using the CO-based disk structure as a starting point, we reproduce the CS J = 7─6 emission well, demonstrating that the CS (which is more sensitive to nonthermal motions than CO) agrees with the turbulence inferred from the CO fit. Establishing a well-constrained background disk model further allows us to identify residual structures in the moment maps that deviate from the expected emission, revealing localized perturbations that may trace forming planets. This framework provides a powerful general approach for extracting disk structure and nonthermal broadening directly from molecular line data and can be applied to other disks with high-quality observations.

A Millimeter Methanol Maser Ring Tracing the Deceleration of the Heat Wave Powered by the Massive Protostellar Accretion Outburst in G358.93─0.03 MM1

First Author: Hunter, T. R.
Instruments: ALMA_Band_5, ALMA_Band_6
ProgramIDs: 2018.A.00031.T, 2019.1.00768.S
BibCode: 2026ApJ...997L..21H

We present multiepoch, multiband Atacama Large Millimeter/submillimeter Array imaging of the new Class II millimeter methanol masers excited during the accretion outburst of the massive protostar G358.93−0.03 MM1. The highest angular resolution image (24 mas ≍160 au) reveals a nearly complete, circular ring of strong maser spots in the 217.2992 GHz (v_t = 1) maser line that closely circumscribes the dust continuum emission from MM1. Weaker maser emission lies inside the eastern and southern halves of the maser ring, generally coincident with the centimeter masers excited during the outburst but avoiding the densest parts of the hot core gas traced by high excitation lines of CH₃CN. Using a variety of fitting techniques on the image cubes of the two strongest maser lines, each observed over three to four epochs, we find the diameter of the ring increased by ≳60% (from ≍1100 to ≍1800 au in the 217 GHz line) over 200 days, consistent with an average radial propagation rate of ≍0.01c, while the maser intensity declined exponentially. Fitting the angular extent of the millimeter masers versus time yields a power law of index 0.39 ± 0.06, which also reproduces the observed extent of the 6.7 GHz masers in the first very long baseline interferometry epoch of R. A. Burns et al. 2020 This exponent is consistent with the prediction of radius versus time in the Taylor─von Neumann─Sedov self-similar solution for an intense spherical explosion from a point source (R ∝ t^2/5). These results demonstrate the explosive nature of accretion outbursts in massive protostars and their ability to generate subluminal heat waves traceable by centimeter and millimeter masers for several months as the energy traverses the surrounding molecular material.

ALMA Band 7 Observations of Water Lines in the Protoplanetary Disk of V883 Ori

First Author: Nakasone, Hiroto
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2021.1.00115.S, 2021.1.00186.S
BibCode: 2026ApJ...998...53N

The FU Orionis star V883 Ori provides a unique opportunity to probe the water snowline in a protoplanetary disk. During an accretion burst, the enhanced stellar luminosity heats the disk, sublimating ices and bringing volatile species into the gas phase. The water snowline, located at ∼80 au in the midplane, represents a key boundary for dust growth and volatile delivery to forming planets. We present Atacama Large Millimeter/submillimeter Array Band 7 observations of V883 Ori that detect two targeted water isotopologue transitions: para-H₂ ¹⁸O 5_1,5─4_2,2 at 322 GHz and HDO 3_3,1─4_2,2 at 335 GHz. After correcting for Keplerian rotation, we detect HDO and H₂ ¹⁸O at 23.6σ and 9.3σ, respectively. Rotational-diagram analysis using a Markov Chain Monte Carlo approach yields T_rot = 116.89 ± 12.81 K and N = (4.90 ± 1.69) × 10¹⁵ cm⁻² for H₂ ¹⁸O and T_rot = 87.46 ± 4.95 K and N = (4.47 ± 0.62) × 10¹⁵ cm⁻² for HDO. These results imply water vapor abundances of NH2O/NH2∼3×10−7 ─5 × 10⁻⁶ and an HDO/H₂O ratio of (0.4─2.0) × 10⁻³ just inside the water snowline, broadly consistent with inheritance from protostellar envelopes. The HDO line in Band 7 is significantly weaker than predicted from Band 6 extrapolation, showing only ∼26% of the expected strength. This attenuation can be explained by a more compact, hotter emitting region with an effective radius of ∼53 au and/or frequency-dependent dust absorption that enlarges the apparent inner cavity at a higher frequency. Our results highlight both the diagnostic power of water isotopologue lines and the need for higher angular resolution observations to resolve the water snowline and test these scenarios.

Continued Rapid Radio Brightening of the Tidal Disruption Event AT2018hyz

First Author: Cendes, Yvette
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2021.1.01210.T
BibCode: 2026ApJ...998..111C

We present ongoing radio observations of the tidal disruption event (TDE) AT2018hyz, which was first detected in the radio at 972 days after disruption, following multiple nondetections from earlier searches. The new observations presented here span ≍1370─2160 days and 0.88─240 GHz. We find that the light curves continue to rise at all frequencies during this time period, following a power law of about F_ν ∝ t³ (compared to F_ν ∝ t^5.7 at 972─1400 days) and reaching a peak luminosity of L ≍ 10⁴⁰ erg s⁻¹, comparable to the luminosity of the relativistic TDE Sw 1644+57 on the same timescale. The multifrequency data indicate that the peak frequency does not significantly evolve over the 1030 days span of our observations, while the peak flux density increases by an order of magnitude. The observed behavior is consistent with two possible scenarios: (i) a delayed spherical outflow launched about 620 days postdisruption with a velocity of ≍0.3c and an energy of ∼10⁵⁰ erg; or (ii) a highly off-axis (≍80°─90°) relativistic jet with a Lorentz factor of Γ ∼ 8 and E_K ≍ 10⁵² erg. Continued radio observations to capture the light-curve peak, as well as very long baseline interferometry observations, could distinguish between these scenarios.

RIOJA. A Clumpy Galaxy Assembly at Redshift 6.81 Revealed by JWST

First Author: Mawatari, Ken
Instruments: ALMA_Band_5, ALMA_Band_6, ALMA_Band_8
ProgramIDs: 2018.1.01359.S, 2015.1.01111.S, 2018.1.00429.S, 2018.1.01551.S
BibCode: 2026ApJ...998..119M

Spatially resolved multiwavelength analysis is essential to study galaxy formation and evolution. A UV-bright galaxy COS-2987030247 at z = 6.81 is one of the Rosetta Stones in the epoch of reionization for which JWST NIRSpec Integral Field Spectroscopy, NIRCam imaging, and Atacama Large Millimeter/submillimeter Array data are available thanks to the RIOJA program. We identified the rest-frame optical emission lines from the ionized hydrogen, oxygen, and neon gas. The [O III] 5008 Å line emission and the NIRCam images show a complex kinematical and morphological structure where two bright main and three faint clumps are identified in a 10 kpc extent. The system is not classified as a purely rotation-dominated disk. The multiple clumps are instead consistent with a merger-related origin, including either distinct galaxies in interaction or star-forming clumps formed through tidal gas compression during a merger. The spatially resolved emission line fluxes show that dust attenuation, metal enrichment, and ionization parameter are preferentially enhanced in the star formation peaks. Our spectral energy distribution fitting suggests that the main clumps are in a moderately dust-attenuated star-forming phase (A_V = 0.2─0.3 and SFR(Hα) ∼10 M_⊙ yr⁻¹) with almost zero escape fraction of ionizing photons. In contrast, the subclumps are dust-free and lying on or below the main sequence of star-forming galaxies. These subclumps may work as a perturber that triggers the clumpy starburst in the surrounding gas through the merger event.

ALMA Lensing Cluster Survey: Molecular Gas Properties of Line-emitting Galaxies from a Blind Survey

First Author: Narita, Kanako
Instruments: ALMA_Band_6
ProgramIDs: 2013.1.00999.S, 2018.1.00035.L, 2015.1.01425.S
BibCode: 2026ApJ...998...42N

We present results of a blind search for line-emitting galaxies using Atacama Large Millimeter/submillimeter Array (ALMA) Lensing Cluster Survey data. We detected seven line emitters, one of which is [C II] at z = 6.071, four are CO at z = 0.8─1.1, and the remaining two are possibly CO or [C I] within photometric redshift ranges. Three of the four CO emitters are multiple images of the same galaxy. Compared to previous line-emitter searches in ALMA deep fields, our sample probes molecular gas masses ∼1 dex below the lower bound, thanks to gravitational lensing (typically μ ∼ 4, up to ∼30 in extreme cases). Most emitters are located in a region similar to normal star-forming galaxies in the star formation rate (SFR) versus molecular gas mass plane. To reduce dependence on SFR and stellar mass, we analyzed the molecular gas fraction and depletion timescale as a function of distance from the star formation main sequence. We found that most emitters broadly follow the scaling relations from previous studies, consistent within the intrinsic scatter. In addition, we serendipitously detected the CH N = 1, J = 3/2 → 1/2 Λ-doublet transition from one CO emitter at z = 1.142, representing the first detection of CH from an individual galaxy at cosmological distances through a blind survey. The CH/CO column density ratio of ∼10⁻⁴ is comparable to that of local active galactic nucleus (AGN)-host galaxies, suggesting that CH traces molecular gas associated with AGN activity, possibly irradiated by X-rays.

A 2 au Resolution View by ALMA of the Planet-hosting WISPIT 2 Disk

First Author: Facchini, Stefano
Instruments: ALMA_Band_7
ProgramIDs: 2024.A.00064.S
BibCode: 2026ApJ...998L..16F

We present deep, high-spatial-resolution interferometric observations of 0.88 mm continuum emission from the TYC 5709-354-1 system, hereafter WISPIT 2, obtained with the goal of detecting circumplanetary emission in the vicinity of the newly discovered WISPIT 2b planet. Observations with the most extended baseline configuration offered by the Atacama Large Millimeter/submillimeter Array, achieving an angular resolution of 25 × 17 mas (3.3 × 2.2 au), revealed a single, narrow ring with a deprojected radius of 144.4 au and width of 7.2 au, and no evidence of circumplanetary emission within the cavity. Injection and recovery tests demonstrate that these observations can rule out pointlike emission at the location of WISPIT 2b brighter than ≍ 45 μJy at the 3σ level. While these data can rule out PDS 70 c-like circumplanetary emission, the upper limit is consistent with empirical mass─flux relationships extrapolated from the stellar regime. Visibility modeling of the continuum ring confirms that WISPIT 2b lies significantly interior to the millimeter dust ring, raising doubts about the ability of WISPIT 2b to be the only driver of the dust structure. Possible solutions include either another lower-mass companion, residing between WISPIT 2b and the cavity edge, likely in the gap seen by SPHERE at ∼130 au, or that WISPIT 2b is either substantially more massive than estimates based on IR photometry (∼15 M_Jup) or on a moderately eccentric orbit. The combination of observations sensitive to the gas and dust distributions on larger spatial scales and dedicated hydrodynamical modeling will help differentiate between scenarios.

Magellanic Outflow and Chemistry Survey (MAGOS): Hot Cores in the LMC

First Author: Shimonishi, Takashi
Instruments: ALMA_Band_7
ProgramIDs: 2019.1.01770.S
BibCode: 2026ApJS..282...64S

The Large Magellanic Cloud (LMC) provides a key laboratory for exploring the diversity of star formation and interstellar chemistry under subsolar metallicity conditions. We present the results of a hot core survey toward 30 massive protostellar objects in the LMC using the Atacama Large Millimeter/submillimeter Array at 350 GHz. Continuum imaging reveals 36 compact sources in total, among which line analyses identify nine hot cores and one hot-core candidate, including two newly identified sources. We detect CO, HCO+, H¹³CO⁺, HC¹⁵N, HC₃N, SiO, SO, SO⁺, NS, SO₂, ³⁴SO₂, ³³SO₂, CH₃OH, ¹³CH₃OH, HCOOH, HCOOCH₃, CH₃OCH₃, C₂H₅OH, H₂CCO (tentative), and hydrogen recombination lines from hot cores. CH₃OCH₃, a complex organic molecule (COM) larger than CH₃OH, is detected for the first time in a hot core outside the LMC bar region. All hot cores show stronger emission in the high-excitation SO line compared to non-hot-core sources, suggesting that its strong detection will be useful for identifying hot-core candidates in the LMC. Chemical analysis reveals a spread of more than 2 orders of magnitude in CH₃OH abundances, with some sources deficient in COMs. In contrast, SO₂ is detected in all hot cores, and its abundance shows a good correlation with rotational temperature. The hot cores without CH₃OH detections are all located outside the LMC bar region and are characterized by either high luminosity or active star formation in their surroundings. A combination of locally low metallicity, active star formation in the vicinity, and high protostellar luminosity may jointly trigger the COM-poor hot-core chemistry observed in the LMC.

The ALPINE-CRISTAL-JWST Survey: Stellar and Nebular Dust Attenuation of Main-sequence Galaxies at z ∼ 4─6

First Author: Tsujita, Akiyoshi
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.00428.L, 2021.1.00280.L
BibCode: 2026ApJ...997..319T

Characterizing dust attenuation is crucial for revealing the intrinsic physical properties of galaxies. We present an analysis of dust attenuation in 18 spectroscopically confirmed star-forming main-sequence galaxies at z = 4.4−5.7 observed with JWST/NIRSpec IFU and NIRCam, selected from the ALPINE and CRISTAL ALMA large programs. We fit the emission-line fluxes from NIRSpec and the broadband photometry from NIRCam with PROSPECTOR, using both spatially integrated emission and ∼0.6 kpc pixel-by-pixel measurements. We derive the stellar-to-nebular dust attenuation ratio (f = E(B − V)_star/E(B − V)_neb) from the SED fits and the Balmer decrement with Hα and Hβ. Although individual galaxies show large scatter, the best-fit value is f=0.51−0.03+0.04 , slightly higher than that measured for local starburst galaxies. We find weak correlations of f with galaxy properties, increasing with higher specific star formation rates, younger stellar ages, and more recent star formation. For the range of E(B − V)_star = 0.009−0.15 mag for in our sample, assuming f = 1 (often adopted in high-redshift studies) instead of f = 0.51 leads to the underestimation of line luminosities and ionizing photon production efficiency ξ_ion by ∼3%−36% and ∼4%−46%, respectively. Finally, total stellar masses estimated from spatially integrated SED fits with delayed-τ star formation histories are systematically smaller than the sums of pixel-by-pixel SED fits by a median of ∼0.26 dex, likely because the integrated fits are biased toward luminous young stellar populations.

The ALMA-QUARKS Survey: Hot Molecular Cores Are a Long-standing Phenomenon in the Evolution of Massive Protostars

First Author: Meng, Dezhao
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2019.1.00685.S, 2021.1.00095.S
BibCode: 2026ApJ...997..340M

We present an analysis of the QUARKS survey sample, focusing on protoclusters where hot molecular cores (HMCs; traced by CH₃CN (12─11)) and HC/UC H II regions (traced by H30α/H40α) coexist. Using the high-resolution, high-sensitivity 1.3 mm data from the QUARKS survey, we identify 125 hot molecular fragments (HMFs), which represent the substructures of HMCs at higher resolution. From line integrated intensity maps of CH₃CN (12₃─11₃) and H30α, we resolve the spatial distribution of HMFs and HC/UC H II regions. By combining with observations of ¹²CO (2─1) outflows and 1.3 mm continuum, we classify HMFs into four types: HMFs associated with jetlike outflow, wide-angle outflow, and nondetectable outflow and shell-like HMFs near HC/UC H II regions. This diversity possibly indicates that the hot core could be a polymorphic and long-standing phenomenon in the evolution of massive protostars. The separation between HMFs and H30α/H40α emission suggests that sequential high-mass star formation within young protoclusters is not likely related to feedback mechanisms.

MINDS. Anatomy of a Water-rich, Inclined, Brown Dwarf Disk: Lack of Abundant Hydrocarbons

First Author: Perotti, Giulia
Instruments: ALMA_Band_7
ProgramIDs: 2012.1.00743.S
BibCode: 2026ApJ...997..281P

2MASS J04381486+2611399 (or J0438) is one of the few young brown dwarfs (BDs) with a highly inclined (i ∼ 70°) disk. Here we report results from JWST Mid-Infrared Instrument (MIRI) Medium Resolution Spectroscopy, Hubble Space Telescope (HST) Advanced Camera for Surveys, and Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations. Despite its late spectral type (M7.25), the spectrum of J0438 resembles those of inner disks around earlier-type stars (K1─M5, T Tauri stars), with a volatile reservoir lacking hydrocarbons (except for acetylene, C₂H₂) and dominated by water. Other identified species are H₂, CO₂, HCN, [Ar⁺], and [Ne⁺]. The dominance of water over hydrocarbons is driven by multiple factors such as disk dynamics, young disk age, low accretion rate, and possible inner disk clearing. J0438 appears highly dynamic, showing a seesaw-like variability and extended emission in H₂ S(1), S(3), S(5), [Ne⁺], and CO (J = 3─2). Interestingly, the CO emission reaches up to 400 au from the BD, suggesting ongoing infalling/outflowing activity impacting the disk chemistry. These observations underscore the combined power of MIRI, HST, and ALMA in characterizing the chemical diversity and dynamics of BD disks.

Resolving the terrestrial planet-forming region of HD 172555 with ALMA: I. Post-impact dust distribution

First Author: Roumeliotis, Z.
Instruments: ALMA_Band_7
ProgramIDs: 2022.1.00793.S
BibCode: 2026A&A...706A...4R

Context. Giant impacts between planetary embryos are a natural step in the terrestrial planet formation process and are expected to create disks of warm debris in the terrestrial regions of their stars. Understanding the gas and dust debris produced in giant impacts is vital for comprehending and constraining models of planetary collisions. Aims. We reveal the distribution of millimeter (mm) grains in the giant impact debris disk of HD 172555 for the first time, using new ALMA 0.87 mm observations at ∼80 mas (2.3 au) resolution. Methods. We modeled the interferometric visibilities to obtain basic spatial properties of the disk and compared these data to the disk's dust and gas distributions at other wavelengths. Results. We detected the star and dust emission from an inclined disk out to ∼9 au and down to 2.3 au (on-sky) from the central star, with no significant asymmetry in the dust distribution. The radiative transfer modeling of the visibilities indicates the disk surface density distribution of mm grains most likely peaks around ∼5 au, while the width inferred remains model-dependent at the S/N of the data. We highlighted an outward radial offset of the small grains traced by scattered light observations compared to the mm grains, which could be explained by the combined effect of gas drag and radiation pressure in the presence of large enough gas densities. Furthermore, our SED modeling implies a size distribution slope for the mm grains consistent with the expectation of collisional evolution and flatter than inferred for the micron-sized grains, implying a break in the grain size distribution and confirming an overabundance of small grains.

Clumpy, Dense Gas in the Outflow of NGC 1266

First Author: Otter, Justin Atsushi
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2011.0.00511.S
BibCode: 2026ApJ...997..361O

Outflows are one of the most spectacular mechanisms through which active galactic nuclei (AGN) impact their host galaxy, though the role of AGN-driven outflows in global star formation regulation across the galaxy population is unclear. NGC 1266 is an excellent case study for investigating outflows and star formation quenching because it is a nearby (D ∼ 30 Mpc) AGN host galaxy with an outflow driving shocks through the interstellar medium (ISM) and has recently quenched its star formation outside the nucleus. While previous works have studied the molecular outflow from its CO emission, to fully characterize the impact the outflow has on the ISM observations probing the dense, cold gas are necessary. Our Atacama Large Millimeter/submillimeter Array Cycle 0 observations do not detect a molecular outflow in ¹³CO(2─1) and yield a lower limit of ¹²CO/¹³CO ≥ 250, suggesting a highly optically thin CO outflow with low ¹³CO abundance. In contrast, we detect substantial HCN(1─0) emission in the outflow, with an HCN(1─0)/¹²CO(1─0) ratio of 0.09, consistent with global measurements of many star-forming galaxies and luminous infrared galaxies. We conclude that the CO emission traces a diffuse component of the molecular gas with a low optical depth, whereas the HCN(1─0) traces dense clumps of gas entrained in the outflow. We measure an upper limit molecular outflow rate of <85 M_⊙ yr^─1. Assuming the ongoing nuclear star formation and outflow continue at the same rates, NGC 1266 will deplete its gas reservoir in 450 Myr or longer, indicating that relatively low-level AGN feedback is capable of gradually expelling the molecular gas reservoir after a rapid quenching event.

JWST reveals extended stellar disks for ALMA-bright dusty star-forming galaxies in the Spiderweb protocluster

First Author: Zhang, Y. H.
Instruments: ALMA_Band_6
ProgramIDs: 2021.1.00435.S
BibCode: 2026A&A...706A...9Z

We present JWST/NIRCam imaging of dusty star-forming galaxies (DSFGs) detected by the Atacama Large Millimetre/submillimetre Array (ALMA) in the Spiderweb protocluster at z = 2.16. We identified 22 DSFGs detected by both ALMA and JWST, ten of which are spectroscopically confirmed as protocluster members. This is the first systematic analysis of a statistical DSFG sample in z ∼ 2 protocluster environments using JWST/NIRCam data. Most of the DSFG members exhibit red colours and reside in the dusty star-forming region of the rest-frame UVJ diagram, indicating strong dust obscuration. The Gini-M₂₀ diagram suggests that most DSFGs in this protocluster are late-type disks, with a significant fraction displaying clumpy and disturbed rest-frame UV/optical morphologies, but few showing clear merger signatures. The DSFG members exhibit relatively large stellar disks and effective radii with a median stellar mass of log(M/M_⊙) = 10.8 ± 0.3, placing them above coeval field DSFGs and typical protocluster galaxies in the size─mass relation at both rest-frame optical and near-infrared wavelengths. These sizes are comparable to those of more evolved field DSFGs at z ∼ 1 − 2, indicating accelerated structural growth in dense environments. Moreover, these DSFG members show a decreasing trend in stellar size from shorter to longer wavelengths, with a moderately steep slope comparable to coeval field DSFGs. These results may support an inside-out growth scenario for protocluster evolution, in which massive galaxies near the centre are more evolved and more strongly affected by active galactic nucleus feedback and environmental effects, for example, ram-pressure stripping. We propose that the cold gas accretion at the protocluster outskirts drives intense star formation and stellar disk growth in ALMA-detected DSFGs, which are expected to evolve into massive elliptical galaxies at later stages.

Zooming into the water snow line: High-resolution water observations of the HL Tau disk

First Author: Leemker, M.
Instruments: ALMA_Band_5, ALMA_Band_7
ProgramIDs: 2017.1.01178.S, 2022.1.00905.S, 2017.1.01562.S, 2021.1.01310.S
BibCode: 2026A&A...705A.193L

Context. Water is one of the central molecules for the formation and habitability of planets. In particular, the region where water freezes out, the water snow line, could be a favorable location for planets to form in protoplanetary disks. Aims. We aimed to spatially resolve the water emission in the HL Tau disk using high-resolution ALMA observations of the H₂O 183 GHz line (E_u = 205 K). We compared the spatially resolved H₂O emission with that of H¹³CO⁺, a chemical tracer of the water snow line, to observationally test their anticorrelation. In addition, we aimed to quantify the fraction of the water reservoir hidden by optically thick dust at ALMA wavelengths versus far- and mid-IR wavelengths. Methods. We used high-resolution ALMA observations to spatially resolve the H₂O 3_1,3─2_2,0 line at 183 GHz, H¹³CO⁺ J = 2─1, and the SO 4₄─3₃ transition in the HL Tau disk. A rotational diagram analysis was used to characterize the water reservoir seen with ALMA and compare it to the reservoir visible at mid- and far-IR wavelengths. Results. We find that the H₂O 183 GHz line has a compact central component and a diffuse component that is seen out to ∼75 au. A radially resolved rotational diagram shows that the excitation temperature of the water is ∼350 K, independent of radius. The steep drop in the water brightness temperature outside the central beam of the observations where the emission is optically thick is consistent with the water snow line being located inside the central beam (≲6 au) at the height probed by the observations. Comparing the ALMA lines to those seen at shorter wavelengths shows that only 0.02─2% of the water reservoir is visible at mid- and far-IR wavelengths due to optically thick dust hiding the emission, whereas 35─70% is visible with ALMA. An anticorrelation between the H₂O and H¹³ CO⁺ emission is found, but it is likely caused by optically thick dust hiding the H¹³CO⁺ emission in the disk center. Finally, we see SO emission tracing the disk and, for the first time in SO, a molecular outflow and the infalling streamer out to ∼2^''. The velocity structure hints at a possible connection between the SO and the H₂O emission. Conclusions. Spatially resolved observations of H₂O lines at (sub)millimeter wavelengths provide valuable constraints on the location of the water snow line while probing the bulk of the gas-phase reservoirs.

PRUSSIC: III. ALMA and NOEMA survey of dense gas in high-redshift star-forming galaxies

First Author: Rybak, M.
Instruments: ALMA_Band_3
ProgramIDs: 2023.1.00432.S, 2017.1.01694.S, 2016.1.00633.S, 2018.1.00747.S
BibCode: 2026A&A...706A..69R

Characterising the relationship between dense gas and star formation is critical for understanding the assembly of galaxies throughout cosmic history. However, due to the faintness of standard dense-gas tracers ─ HCN, HCO⁺, and HNC ─ dense gas in high-redshift galaxies remains largely unexplored. We present ALMA and NOEMA observations targeting HCN/HCO⁺/HNC (3─2) and (4─3) emission lines in 11 (mostly) gravitationally lensed dusty star-forming galaxies (DSFGs) at redshift z = 1.6 − 3.2. We detect at least one line in 10 out of 11 galaxies. Altogether, we detect 34 dense-gas transitions, more than quadrupling the number of extant high-redshift detections. Additionally, in two targets, we detect lower-abundance CO isotopologues ¹³CO and C¹⁸O, as well as CN emission. We derive excitation coefficients for HCN, HCO⁺, and HNC in DSFGs, finding them to be systematically higher than those in nearby luminous infrared galaxies. Assuming the canonical dense-mass conversion factor (α_HCN = 10), we find that DSFGs have shorter dense-gas depletion times (median 23 Myr) than nearby galaxies (≍60 Myr), with a star-forming efficiency per free-fall time of 1−2%, a factor of a few higher than in local galaxies. We find a wide range of dense-gas fractions, with HCN/CO ratios ranging between 0.01 and 0.15. Finally, we put the first constraints on the redshift evolution of the cosmic dense-gas density, which increases by a factor of 7 ± 4 between z = 0 and z = 2.5, consistent with the evolution of the cosmic molecular-gas density.

Turbulence and dust fragility in protoplanetary discs

First Author: Tong, Simin
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_6
ProgramIDs: 2016.1.01158.S, 2017.1.01151.S, 2018.1.01230.S, 2015.1.00490.S
BibCode: 2026MNRAS.545f2128T

Dust growth from micron- to planet-size in protoplanetary discs involves multiple physical processes, including dust collisions, the streaming instability, and pebble accretion. Disc turbulence and dust fragility matter at almost every stage. Previous studies typically vary one of them while fixing the other, failing to provide a complete picture. Here, we use analytical models and numerical dust evolution models DUSTPY to study the combinations of gas turbulence and dust fragility that can reproduce multiwavelength Atacama Large Millimetre/submillimetre Array (ALMA) observables. We find that only appropriate combinations ─ fragile dust (

$v_\mathrm{frag}$

= 1─

$2~\mathrm{m~s^{-1}}$

) in discs with viscous

$\alpha =10^{-4}$

or resilient dust (

$v_\mathrm{frag}$

= 6─

$10~\mathrm{m~s^{-1}}$

) in discs with viscous

$\alpha =10^{-3}$

─ can reproduce observations. Our result is robust to two widely used opacities (DSHARP and Ricci opacities). Regardless of the strength of disc turbulence, reproducing observations requires observed dust rings to be optically thick at

$\lambda =1.3$

and 3 mm. As only small dust can be lifted above the mid-plane to reach the emitting layers, SED analysis probably yields lower limits on the maximum grain sizes. We highlight the challenge of creating detectable dust rings at large radii when incorporating bouncing in models, and the need for earlier formation of dust rings at smaller radii to reproduce the decreasing ring brightness with radius observed across ALMA wavelengths.

X-ray, optical, and radio follow-up of five thermally emitting isolated neutron star candidates

First Author: Kurpas, J.
Instruments: FORS2
ProgramIDs: 111.259R
BibCode: 2026A&A...705A.148K

We report on follow-up observations with XMM-Newton, the FORS2 instrument at the ESO-VLT, and FAST, aiming to characterise the nature of five thermally emitting isolated neutron star (INS) candidates recently discovered from searches in the footprint of the Spectrum Roentgen Gamma (SRG)/eROSITA All-sky Survey. We find that the X-ray spectra are predominantly thermal and can be described by low-absorbed blackbody models with effective temperatures ranging from 50 to 210 eV. In two sources, the spectra also show narrow absorption features at 300─400 eV. Additional non-thermal emission components are not detected in any of the five candidates. The soft X-ray emission, the absence of optical counterparts in four sources, and the consequent large X-ray-to-optical flux ratios > 3000 − 5400 confirm their INS nature. For the remaining source, eRASSU J144516.0─374428, the available data do not allow a confident exclusion of an active galactic nucleus nature. However, if the source is Galactic, the small inferred X-ray emitting region is reminiscent of a heated pulsar polar cap, possibly pointing to a binary pulsar nature. X-ray timing searches do not detect significant modulations in all candidates, implying pulsed fraction upper limits of 13─19% (0.001─13.5 Hz). The absence of pulsations in the FAST observations targeting eRASSU J081952.1─131930 and eRASSU J084046.2─115222 excludes periodic magnetospheric emission at 1─1.5 GHz with an 8σ significance down to 4.08 μJy and 2.72 μJy, respectively. The long-term X-ray emission of all sources does not imply significant variability. Additional observations are warranted to establish exact neutron star types. At the same time, the confirmation of the predominantly thermal neutron star nature in four additional sources highlights the power of SRG/eROSITA to complement the Galactic INS population. ★ Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA (observations 0921280301, 0921280401, 0921280501, 0921280601, 0921280701).

MINDS: Young binary systems with JWST/MIRI: Variable water-rich primaries and extended emission

First Author: Kurtovic, Nicolás T.
Instruments: ALMA_Band_6, CRIRES
ProgramIDs: 110.244F, 2015.1.01506.S, 2016.1.00877.S, 2016.1.01164.S, 2017.1.01631.S, 2018.1.00973.S, 2019.1.01739.S, 2021.1.00854.S
BibCode: 2026A&A...705A..97K

Context. Dynamical disk-companion interactions can have a significant impact on the evolution of circumstellar disks, as these can produce perturbations to the material distribution, density, and temperature, affecting their potential for planet formation. Aims. As part of the JWST GTO program MINDS, we analyze the mid-infrared (MIR) emission of three Class II binary systems: VW Cha, WX Cha, and RW Aur. Our aim is to investigate the impact of stellar multiplicity on the chemistry and physics of their inner disk. Methods. We analyzed the 1D spectrum from JWST/MIRI-MRS for primary and secondary disks separately, extracted via a combination of forward modeling with a theoretical PSF and aperture photometry. Following the continuum subtraction, we modeled the molecular lines with 0D slab models. We interpreted the results by comparing our JWST spectra to VLT/CRIRES+, Spitzer/IRS. The extended MIR emission was compared to ALMA data, with the inclusion of the binary DF Tau in our sample. Results. Primary and secondary disks are dramatically different in their MIR emission, with primary disks exhibiting H₂O-rich spectra and secondary disks being mostly line-poor with respect to the sensitivity of our spectra. When comparing MIRI-MRS to Spitzer/IRS, we observed a broad variability in the line emission of VW Cha A and in the continuum of RW Aur A. The disks around VW Cha BC and RW Aur B show evidence of ionizing radiation and a further comparison with ALMA at high angular resolution dust continuum suggests that the spectrum of RW Aur B is well explained by its ~4 au cavity. All the systems show [Ne II] jet emission and three of them also show spatially resolved emission structures in H₂, likely originating from outflows and dynamical interactions. Conclusions. Many of the observed features in the primary disks, such as enhanced water emission, could be linked to the increased accretion and radial drift produced by dynamical disk truncation. However, additional mechanisms are needed to explain the large differences between primary and secondary disks, potentially inner disk substructures. This work highlights the need for combining data from multiple facilities to fully understand the observations from JWST.

SMSS J022423.27−573705.1: An Extremely Metal-poor Star with the Most Pronounced Weak r-process Signature

First Author: Okada, Hiroko
Instruments: UVES
ProgramIDs: 0101.D-0677
BibCode: 2026ApJ...997..119O

We present the measurement of 26 elemental abundances of SMSS J022423.27−573705.1 (SMSS 0224─5737), an extremely metal-poor (EMP) star with a weak r-process signature. We report the measurements of N, O, V, Zn, and Ba, and the upper limits for Mo, Ru, Pd, Ag, and Eu for the first time. SMSS 0224─5737 exhibits low C abundance and high N and O abundances, suggesting that C is converted to N by the enhanced mixing during the evolution. The abundance pattern up to the Fe-peak elements is generally in good agreement with the average abundance of EMP stars, although a notable feature is the high [Zn/Fe] ratio ([Zn/Fe] = + 0.88). We confirm the enhancement of the first-peak neutron-capture elements (Sr, Y, and Zr) and determine a low Ba abundance [Ba/H] = −5.25, that is, [Ba/Fe] = −1.45. The extremely high ratio of [Zr/Ba] = +2.60 makes SMSS 0224─5737 the EMP star with the most pronounced weak r-process signature observed to date. The abundance pattern of the neutron-capture elements is compared with the yields from r-process nucleosynthesis models. The sharp decline in abundances beyond Zr disfavors neutron star merger or electron-capture supernova models, but is reproduced either by protoneutron star wind models or by magneto-rotational supernova models. Considering the high [Zn/Fe] ratio, a magnetorotational supernova is the most plausible origin of SMSS 0224─5737. This study demonstrates that the abundance measurements of both light and neutron-capture elements, even at low abundances, are crucial for unveiling the astrophysical sites of the weak r-process.

A Deep Chandra View of A2597: Bubbles, Shocks, Cold Fueling, and a Plasma Depletion Layer

First Author: Omoruyi, Osase
Instruments: SINFONI
ProgramIDs: 093.B-0638
BibCode: 2026ApJ...997..114O

To examine how active galactic nucleus (AGN) feedback shapes the intracluster medium (ICM) and fuels black hole accretion in the cool-core galaxy cluster A2597, we present deep (∼600 ks) Chandra X-ray observations complemented by archival GMRT radio and SINFONI near-infrared data. Radio-mode AGN activity has inflated seven X-ray cavities and driven one to three potential weak shocks ( M∼1.05−1.14 ) extending to ∼150 kpc, suggesting recurrent outbursts occurring on ∼10⁷ yr timescales. We also detect a narrow, ∼57 kpc X-ray surface brightness deficit—a potential plasma depletion layer—likely shaped by residual sloshing motions that amplified magnetic fields and/or displaced gas within the cluster core. Although the AGN injects ∼10⁴⁴ erg s⁻¹ of energy, comparable to the cluster's cooling luminosity, radiative cooling persists at ∼15 M_⊙ yr⁻¹, replenishing the billion-solar-mass cold gas reservoir at the heart of the brightest cluster galaxy. Sustaining this level of activity requires a continuous fuel supply, yet the estimated Bondi accretion power (∼2 × 10⁴³ erg s⁻¹) falls an order of magnitude short of the observed cavity power, suggesting that "hot" gas fueling is insufficient. Instead, archival Atacama Large Millimeter/submillimeter Array observations continue to support a chaotic cold accretion scenario, where turbulence-driven condensation fuels the AGN at rates exceeding Bondi accretion, sustaining a self-regulated feedback cycle that repeatedly shapes the core of A2597.

Mapping the Cosmic-Ray Ionization Rate in the Local Galaxy with H3+ First Author: Indriolo, Nick
Instruments: CRIRES, UVES
ProgramIDs: 194.C-0833, 088.C-0351, DataDoiProID
BibCode: 2026ApJ...997..123I

Chemistry in diffuse molecular clouds relies primarily on rapid ion-molecule reactions. Formation of the initial ions, H⁺ and H 2+ , is dominated by cosmic-ray ionization of H and H₂, making the cosmic-ray ionization rate (denoted ζ(X) for species X) an important parameter for chemical modeling. We have made observations targeting absorption lines of H 3+ , one of the most reliable tracers of ζ(H₂), toward diffuse molecular cloud sight lines where the H₂ column density has been directly measured in the ultraviolet, detecting H 3+ in 12 out of 27 sight lines. The 3D-PDR modeling method introduced by M. Obolentseva et al. was used to infer cosmic-ray ionization rates in the clouds along these sight lines, and our combined sample has a mean ionization rate of 5.3 × 10⁻¹⁷ s⁻¹ with standard deviation 2.5 × 10⁻¹⁷ s⁻¹. By associating H 3+ absorption with gas density peaks derived from the differential extinction maps of G. Edenhofer et al., we have constructed a sparsely sampled 3D map of the cosmic-ray ionization rate in targeted regions within about 1 kpc of the Sun. Specific regions show reasonably uniform ionization rates over length scales of tens of parsecs, with the average ionization rate in each region being different. Large differences (factor of 5) in ζ(H₂) are found over length scales of about 100 pc. This supports a picture where the cosmic-ray ionization rate varies smoothly over small size scales, but is not uniform everywhere in the Galactic disk, likely being controlled by proximity to particle acceleration sites.

The MATISSE view of the inner region of the RY Tau protoplanetary disk

First Author: Martin, J. S.
Instruments: MATISSE
ProgramIDs: 106.21Q8
BibCode: 2026A&A...705A.182M

Context. The physical conditions and processes taking place in the innermost regions of protoplanetary disks are essential for planet formation and general disk evolution. In this context, we study the T-Tauri type young stellar object RY Tau, which exhibits a dust-depleted inner cavity characteristic of a transition disk. Aims. The goal of this study is to analyze spectrally resolved interferometric observations in the L, M, and N bands of the RY Tau protoplanetary disk obtained with MATISSE. We aim to provide constraints on the spatial distribution and mineralogy of dust in the inner few astronomical units by producing synthetic observations fitting the interferometric observables. Methods. We employed a 2D temperature gradient disk model to estimate the orientation of the inner disk. Successively, we analyzed the chemical composition of silicates depending on spatial region in the disk. Finally, we sampled the parameter space of a viscous accretion disk model via Monte Carlo radiative transfer simulations to investigate the actual 3D dust density distribution of RY Tau. Results. We constrained the orientation of the inner disk of RY Tau, finding no evidence of significant misalignment with respect to its outer disk. We identified several silicate species commonly found in protoplanetary disks and observed a depletion of amorphous dust grains toward the central protostar. By simultaneously considering the observed visibilities and the spectral energy distribution (SED), we found that an accretion disk and an optically thin envelope enshrouding the protostar fits the observations best. Radiative transfer simulations show that hot dust close to the protostar and in the line of sight (LOS) to the observer, either in the uppermost disk layers of a strongly flared disk or in a dusty envelope, is necessary to model the observations. The shadow cast by a dense innermost disk midplane on the dust further out explains the observed closure phases in the L band and (to some extent) in the M band. However, the closure phases in the N band are underestimated by our model, hinting at an additional asymmetry in the flux density distribution that is not visible at shorter wavelengths.

The VVVX quest for satellites around the Circinus galaxy

First Author: Baravalle, L. D.
Instruments: VIRCAM
ProgramIDs: 179.B-2002, 198.B-2004
BibCode: 2026A&A...705A.242B

Context. The Circinus galaxy is the nearest type-2 Seyfert galaxy, located at a distance of 4.2 Mpc. Its environment is challenging to explore because of the low Galactic latitudes of its location, behind the disc of the Milky Way. Aims. The long-term goal of this work is to characterise the Circinus galaxy halo. We are also interested in determining the possible presence of dwarf satellites using near-infrared (NIR) data. Methods. We selected 1542 galaxies from the VISTA Variables in the Vía Láctea (VVV) NIR galaxy catalogue within a 2-degree radius around the Circinus galaxy, representing roughly 2/3 of the virial radius. We used structural parameters, such as the half-light radii and colours, and correlations were examined. A neural network was trained with 486 galaxies with known spectroscopic redshifts to estimate photometric redshifts for all of these galaxies. The potential satellites of the Circinus galaxy were defined on the basis of half-light radii that were compatible with the typical sizes of dwarf satellites in galaxies and combined with photometric redshifts. Results. The galaxy properties have been reliably characterised down to K_s ∼ 15.5 mag, representing about 90% completeness of the detections. At the distance of the Circinus galaxy, this limiting magnitude corresponds to a K_s absolute magnitude of −12.6 mag, allowing us to locate dwarf galaxies. In total, there are 20 galaxies with half-light radii larger than 2.45 arcsec, but only 8 of them have photometric redshifts below 0.04. None of these galaxies are close to the Circinus galaxy, which has a redshift of 0.0015 and shows no evidence of associated clustering. The ANNz model exhibited a high degree of accuracy in the range of 0.001 < z_phot < 0.023, thereby validating this method in these extinct regions. Conclusions. The presence of dwarf satellites associated with the Circinus galaxy could not be confirmed with the available data in the studied region. The apparent lack of satellites could be genuine, possibly related to AGN feedback effects. Nevertheless, this work demonstrates the effectiveness of combining near-infrared data and machine learning techniques to estimate photometric redshifts at low Galactic latitudes, thereby providing useful information for future spectroscopic follow-up campaigns.

SDSS-ALMA Legacy Value Archival Gas Exploration (SALVAGE) ─ I. Global star formation is governed by central (not global) molecular gas

First Author: Wilkinson, Scott
Instruments: ALMA_Band_3
ProgramIDs: 2011.0.00374.S, 2012.1.00539.S, 2013.1.00058.S, 2013.1.00096.S, 2013.1.00115.S, 2013.1.00530.S, 2013.1.01383.S, 2015.1.00320.S, 2015.1.00389.S, 2015.1.00405.S, 2015.1.00587.S, 2015.1.00820.S, 2015.1.01012.S, 2015.1.01120.S, 2015.1.01225.S, 2016.1.00177.S, 2016.1.00329.S, 2016.1.00852.S, 2016.1.00948.S, 2016.1.01172.S, 2016.1.01265.S, 2016.1.01269.S, 2017.1.00025.S, 2017.1.00496.S, 2017.1.00601.S, 2017.1.00629.S, 2017.1.01093.S, 2017.1.01727.S, 2018.1.00541.S, 2018.1.00558.S, 2018.1.00940.S, 2018.1.01852.S, 2019.1.00260.S, 2019.1.00597.S, 2019.1.01136.S, 2019.1.01757.S, 2021.1.00094.S, 2021.1.00602.S, 2021.1.01089.S, 2022.1.00482.S
BibCode: 2026MNRAS.545f1980W

Star-forming galaxies form tight relations between their stellar mass, star formation rate, and molecular gas reservoir on global and resolved scales. On the path to quiescence, the exchange between gas and stars must inevitably be broken. Understanding the mechanisms governing star formation and quenching therefore requires observations of both the stellar and molecular gas components. To this end, we have assembled a sample of 277 galaxies (

$0.02 \lesssim z \lesssim 0.25$

) with semiresolved optical and millimetre

$^{12}$

CO (1─0) data, wherein the properties of the inner

$\sim$

2 kpc can be distinguished from the outer regions. This effort was made possible by the Sloan Digital Sky Survey (SDSS) catalogues and the maturing archive of the Atacama Large (sub-)Millimetre Array (ALMA). We call this data set the SDSS-ALMA Legacy-Value Archival Gas Exploration (SALVAGE). In this work, we leverage SALVAGE to provide a semiresolved perspective on global scaling relations and why some galaxies deviate from them. In agreement with previous work, we find that the offset of a galaxy from the global star-forming main sequence (SFMS) is driven by its inner star formation rate. With the relative inner and outer distributions of molecular gas fraction and star formation efficiency, we investigate whether the central star formation driving global changes is due to fuel availability or efficiency. We find that the position of a galaxy within the SFMS is largely due to the inner star formation efficiency, while departure from the SFMS is driven by availability of central gas. The central few kpc are thus the most consequential region for galaxy evolution at low redshift.

Formation of Substructure in Luminous Submillimeter Galaxies (FOSSILS): Evidence of Multiple Pathways to Trigger Starbursts in Luminous Submillimeter Galaxies

First Author: Ikeda, Ryota
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_6, ALMA_Band_7, ALMA_Band_9
ProgramIDs: 2015.1.01345.S, 2016.1.00012.S, 2017.1.00127.S, 2017.1.00487.S, 2017.A.00034.S, 2018.1.00081.S, 2018.1.01136.S, 2019.1.01600.S
BibCode: 2026ApJ...996..121I

We present an analysis of rest-frame optical and far-infrared continuum emission in three luminous submillimeter galaxies (SMGs) at 3.0 ≲ z ≲ 4.5. The SMGs are spatially resolved down to 400─500 pc ( ∼0.″05 ) resolution by James Webb Space Telescope and Atacama Large Millimeter/submillimeter Array observations. Despite similarities in their observed far-infrared properties (flux density, infrared luminosity, and effective radius), the three SMGs exhibit heterogeneous morphologies both across wavelengths and among the sources themselves. While two of them (AzTEC-4 and AzTEC-8) show a disk-like structure in the optical continuum, AzTEC-1 is dominated by a highly concentrated component with a Sérsic index of n = 5.4, where its far-infrared continuum emission is clumpy and less concentrated. AzTEC-4, which is confirmed to be at z = 4.198, shows a two-arm spiral of dust, but not in the stellar distribution. These three SMGs exemplify that multiple physical mechanisms exist in triggering starbursts in luminous SMGs at high redshift: secular instability in gas disks (AzTEC-4) in addition to possible minor mergers (AzTEC-8), and a combination of the efficient gas supply to the central core induced by a gas-rich major merger and the re-formation of a cold gas disk (AzTEC-1).

Zangetsu: A Candidate Isolated, Quiescent, and Backsplash Ultra-diffuse Galaxy in the COSMOS Field

First Author: Wei, Leyao
Instruments: VIRCAM
ProgramIDs: 179.A-2005
BibCode: 2026ApJ...997...32W

Deep imaging surveys have changed our view of the low surface brightness (LSB) Universe. The "renaissance" of the LSB galaxy population, as a prime example of this recent development, continues to challenge our understanding of galaxy formation. Here, we report the serendipitous discovery of Zangetsu, an isolated, quiescent, and distorted ultra-diffuse galaxy (UDG) candidate in the COSMOS field, using images from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Zangetsu exhibits an extremely low central surface brightness (μ_0,g = 26.60 ± 0.01 mag arcsec⁻²), a very shallow inner surface brightness profile (n_Sersic = 0.40 ± 0.01), and a large angular size (R_e ≍ 10 .″ 44). Surprisingly, Zangetsu also has a quiescent stellar population (g − i = 0.96), an unusually elongated shape (b/a ∼ 0.25), and mild morphological asymmetry, making it a rare case among known UDGs. Surface brightness fluctuation analysis of HSC and Hubble Space Telescope images only provides a distance lower limit of D > 25.4 Mpc (thus, R_e > 1.38 kpc). However, Zangetsu remains an extreme outlier in the luminosity─size relation of known LSB galaxies, suggesting that it could be an exceptionally large and/or diffuse system. Classic internal or external UDG formation mechanisms alone struggle to explain such a system. A backsplash origin may account for its isolation and quiescent nature. This finding also raises the possibility that current works may overlook similarly extreme, elongated systems that could further our understanding of the LSB Universe.

Probing the Cosmic Reionization History with JWST: Gunn─Peterson and Lyα Damping Wing Absorption at 4.5 < z < 13

First Author: Umeda, Hiroya
Instruments: VIMOS
ProgramIDs: 194.A-2003
BibCode: 2026ApJ...997...86U

We present a statistical analysis of Lyα absorption using 581 galaxies at z = 4.5─13 observed with multiple JWST/NIRSpec spectroscopy programs, including JADES, UNCOVER, CEERS, and GO/DDT. We carefully construct composite spectra binned by redshift with homogeneous UV properties (UV magnitudes, UV slopes, and Lyα equivalent widths) and identify significant Lyα forest signals in galaxies at z ∼ 5─6, which diminish toward higher redshifts. We also find UV continuum breaks at rest-frame 1216 Å that soften beyond z ≳ 6, confirming the effects of cosmic reionization through a self-consistent transition from Gunn─Peterson to Lyα damping wing absorption in galaxies. Fair comparisons of composite spectra with matched UV magnitudes and slopes across redshift reveal that UV-faint galaxies clearly show stronger Lyα absorption than UV-bright galaxies toward high redshift, providing insights into the topological evolution of reionization. We estimate Lyα transmission at the Gunn─Peterson trough and Lyα damping wing absorption by comparing the galaxy spectra to low-z (z ∼ 2─5) galaxy templates that include galactic and circumgalactic absorption and Lyα emission. Using these measurements together with reionization simulations, we derive volume average neutral hydrogen fractions of H I>= 0.00−0.00+0.12 , 0.25−0.20+0.10 , 0.65−0.35+0.27 , 1.00−0.20+0.00 , and 1.00−0.40+0.00 at z ∼ 5, 6, 7, 9, and 10, respectively. These values broadly align with a reionization history characterized by a rapid transition around z ∼ 7─8, consistent with Lyα emitter observations. While the physical driver of this rapid reionization remains unclear, it may involve the emergence of hidden active galactic nucleus populations and/or the onset of Lyman-continuum escape from galaxies.

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