Latest ESO telbib papers

Astrometric view of companions in the inner dust cavities of protoplanetary discs

First Author: Vioque, Miguel
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_6, ALMA_Band_7, ALMA_Band_8
ProgramIDs: 2012.1.00631.S, 2012.1.00698.S, 2013.1.00291.S, 2013.1.00437.S, 2015.1.00979.S, 2015.1.01301.S, 2015.A.00005.S, 2016.1.00344.S, 2016.1.00484.L, 2016.1.00715.S, 2016.1.01164.S, 2016.1.01286.S, 2016.1.01344.S, 2016.1.01511.S, 2017.1.00388.S, 2017.1.00449.S, 2017.1.00492.S, 2017.1.00969.S, 2017.1.01151.S, 2017.1.01404.S, 2017.1.01460.S, 2017.1.01578.S, 2017.1.01631.S, 2017.1.01678.S, 2018.1.00028.S, 2018.1.00310.S, 2018.1.00350.S, 2018.1.00532.S, 2018.1.00536.S, 2018.1.00689.S, 2018.1.01020.S, 2018.1.01054.S, 2018.1.01055.L, 2018.1.01066.S, 2018.1.01255.S, 2018.1.01302.S, 2018.1.01309.S, 2018.1.01458.S, 2018.1.01755.S, 2018.1.01829.S, 2018.A.00030.S, 2019.1.00566.S, 2019.1.00607.S, 2019.1.00847.S, 2019.1.01059.S, 2019.1.01091.S, 2019.1.01210.S, 2019.1.01270.S, 2021.1.00128.L, 2021.1.00378.S, 2021.1.00709.S, 2021.1.00994.S, 2021.1.01123.L, 2021.1.01137.S, 2021.1.01661.S, 2021.1.01705.S, 2022.1.00154.S, 2022.1.00313.S, 2022.1.00340.S, 2022.1.00646.S, 2022.1.00742.S, 2022.1.00760.S, 2022.1.00908.S, 2022.1.01302.S
BibCode: 2026A&A...705A.238V

Context. Protoplanetary discs with inner dust cavities (often referred to as 'transition discs') are potential signposts of planet formation. However, few companions have been identified within these cavities, and the role of companions in shaping them remains unclear. Aims. We used Gaia astrometry to search for planetary and stellar companions in a sample of 98 transition discs, assessing the occurrence rate of such companions and their potential influence on cavity formation. Methods. For the 98 young stellar objects (YSOs) with inner dust cavities, we computed Gaia proper motion anomalies, which together with the renormalised unit weight error (RUWE), identify companions with mass ratios q ≳0.01 at ∼0.1−30 au. We assessed the impact of disc gravity, accretion, disc-scattered light, dippers, starspots, jets, and outflows on the measured proper motion anomalies, concluding that these effects are unlikely to affect our analyses and that astrometric techniques such as the one of this work can be robustly applied to YSOs. Results. Significant proper motion anomalies are found in 31 transition discs (32% of the sample), indicative of companions. We recovered 85% of the known companions within our sensitivity range. Assuming that the astrometry of each system is dominated by a single companion, we modelled the semi-major axis and mass required to reproduce the observed astrometric signals. Most inferred companions have M>30 M_J, placing many within or near the stellar mass regime. Seven sources host companions compatible with a planetary mass (M<13 M_J, HD 100453, J04343128+1722201, J16102955-3922144, MHO6, MP Mus, PDS 70, and Sz 76). For the non-detections, we provide the companion masses and semi-major axes that can be excluded in future searches. About half (53%) of detected companions cannot be reconciled with having carved the observed dust cavities. Conclusions. We have gathered evidence of the presence of companions in a large sample of transition discs. However, we find that the population of transition discs cannot be fully described as a circumbinary population. Transition discs host as many companions within our sensitivity range as do randomly sampled groups of YSOs and main-sequence stars. If dust cavities are shaped by companions, such companions must reside at larger orbital separations than those of the companions detected here, and we predict them to be of planetary mass.

The ALMA-QUARKS Survey: Evidence of an Explosive Molecular Outflow in IRAS 15520─5234

First Author: Hoque, Ariful
Instruments: ALMA_Band_6
ProgramIDs: 2021.1.00095.S
BibCode: 2026ApJ..1001..161H

We present a study of the massive protocluster IRAS 15520─5234, which displays evidence of an explosive molecular outflow that unleashed a kinetic energy of at least 10⁴⁸ erg. The protocluster contains 16 dense cores detected in the Atacama Large Millimeter/submillimeter Array (ALMA) band 6 continuum emission maps, having masses in the range from 0.2 to 11.0 M_⊙. Our analysis of CO (2−1) emission reveals 28 well-collimated outflow fingers, the majority of which follow a Hubble─Lemaître velocity law. The outflow fingers show no preferred orientation in the plane of sky and emerge from a common center of origin. We estimate the total mass, momentum, and kinetic energy of the outflow fingers and find that the values are at least 1 order of magnitude higher than the typical bipolar outflows associated with massive protostars. The morphology and kinematics of the outflow fingers suggest that the outflow associated with IRAS 15520─5234 is explosive in nature. We calculate the dynamical age of the explosive event to be approximately 6550 yr. Additionally, we estimate the frequency of such explosive outflows in the Galaxy, which is one event every 83 yr. Finally, we speculate that the rearrangement of masses within the massive protocluster and the dynamical interaction among the massive cores may result in the formation of such an energetic event.

Protostellar Outflows Shed Light on the Dominant Close Companion Star Formation Pathways

First Author: Sponzilli, Ryan
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00053.S, 2018.1.01038.S
BibCode: 2026ApJ..1001..134S

Understanding the formation pathway for close-companion protostars is central to unraveling the processes that govern stellar multiplicity and very early star formation. We analyze a large sample of 51 Class 0/I close-companion protostellar systems, of which 38 show detectable outflows, yielding 42 measured outflows used in our analysis. We use Atacama Large Millimeter/submillimeter Array observations of 11 systems in Perseus and 40 systems in Orion. These companions formed either directly at these small scales (≲500 au separations) via disk fragmentation or at larger scales (>1000 au separations) via turbulent fragmentation followed by inward migration. Because of differences in formation mechanism, the former is expected to have preferentially aligned disks and outflows, whereas the latter is expected to show no preferred alignment. The relative prevalence of these formation pathways remains uncertain, yet it is critical to forming a comprehensive picture of star formation. We examine the distribution of position angles (PAs) of companion protostars relative to the PAs of their molecular outflows. The outflow, as traced by ¹²CO (J = 2 → 1), is a useful proxy for the angular momentum of the system, expected to be orthogonal to the binary orbital plane. We use a simple model to account for a random sampling of inclination and orbital phase in each system, finding that the observations are consistent with a distribution where the outflows are preferentially orthogonal to the companions. Based on this analysis, we suggest disk fragmentation is the dominant formation pathway for close-companion protostellar systems.

Stratification of the Active Galactic Nucleus─Driven Multiphase Outflows in the Dwarf Seyfert Galaxy NGC 4395

First Author: Nandi, Payel
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00572.S
BibCode: 2026ApJ..1001..226N

We present a multiwavelength study of nuclear outflows in the nearby dwarf Seyfert galaxy NGC 4395, which hosts an intermediate-mass black hole. Using JWST/NIRSpec and MIRI integral-field-unit spectroscopy (1.66─28.6 μm), together with Atacama Large Millimeter/submillimeter Array (ALMA) and Gemini/GMOS data, we probe the ionized and molecular gas on parsec scales. The JWST nuclear spectra reveal 134 emission lines, including H I, He, numerous fine-structure lines, H₂ rotational/rovibrational transitions, and several polycyclic aromatic hydrocarbon bands. Modelling of the H₂ rotational lines reveals three warm/hot molecular components (T ≍ 580, 1480, and 2900 K), along with a cold (< 50 K) phase traced by ALMA CO(2─1). Outflow signatures are detected in cold and warm/hot molecular gas, in H I, and in 36 fine-structure lines spanning ionization potentials of 7.6─300 eV. Ionized outflow velocities range from 127 to 716 km s⁻¹, with blueshifted and redshifted components consistent with a stratified biconical geometry. The cold molecular gas shows a mass outflow rate nearly 1─2 orders of magnitude larger than that of the warm/hot molecular and ionized phases. The kinetic coupling efficiency is 0.003%─0.12% for the coronal-line gas and 0.4%─1.4% for the H I outflow, indicating that only the low-ionization gas significantly impacts the surrounding ISM. Outflow velocity and the fraction of flux in the outflowing component increase with ionization potential, implying that the most highly ionized gas originates closest to the active galactic nucleus and is most efficiently accelerated.

Linear filament and nested cluster evolution tomography (LANCET): I. Capture the evolution of dense gas in 14-parsec filament G316.8

First Author: Xu, Fengwei
Instruments: ALMA_Band_6
ProgramIDs: 2016.1.00909.S
BibCode: 2026A&A...708A.251X

A dynamic view of mass assembly is essential for understanding the formation of massive stars and clusters. However, interpreting evolutionary diagnostics from Galactic-wide surveys requires careful consideration of distance and environmental variations. The G316.8 filament provides an excellent controlled case: a 14-parsec, nearly linear structure comprising three contiguous subregions with comparable molecular gas reservoirs (each ~10 000 M_⊙), yet spanning a clear evolutionary sequence from a northern infrared dark cloud (young) through a central massive young stellar object (intermediate), to a southern HII region (evolved). The Linear filament and nested cluster evolution tomography (LANCET) project mapped the entire G316.8 filament with the Atacama Compact Array (ACA) at 1.3 mm, achieving 6″ (0.08 pc) resolution over 26.7 arcmin² (17.1 pc²). By combining ACA 7 m data with Herschel and APEX/ArTéMiS observations, we produced high-resolution temperature and column-density maps. We quantified subregional differences using (i) dense-fragment statistics, (ii) column-density probability distribution functions (N-PDFs), and (iii) the scale-dependent structural diagnostic, the ∆-variance. From young to intermediate to evolved, the maximum fragment mass increases from 8 to 160 to 490 M_⊙, while the dense-gas mass fraction (>0.5 g cm⁻²) rises from 0.4 to 2.3 to 9.6%. Along this sequence, the N-PDF develops a slightly flatter primary power-law tail and an additional, steeper secondary tail; the ∆-variance slope becomes progressively shallower. Across G316.8, the subregional differences consistently indicate a coherent evolutionary trend of massive star formation, in which gas is continuously assembled into sub-parsec dense structures. The forthcoming 12 m array observations are about to extend this dynamic picture by resolving dense core formation and probing gas kinematics and magnetic fields.

B Aur, a Rosetta stone for studies of planet formation: IV. C/O estimates from CS and SO interferometric observations

First Author: Rivière-Marichalar, P.
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00579.S, 2021.1.00690.S
BibCode: 2026A&A...707A.348R

Context. Protoplanetary disks are the birthplaces of planets. As such, they set the initial chemical abundances available for planetary atmosphere formation. Thus, studying elemental abundances, molecular compositions, and abundance ratios in protoplanetary disks is key to linking planetary atmospheres to their formation sites. Aims. We aim to derive the sulfur abundance and the C/O ratio in the AB Aur disk using interferometric observations of CS and SO. Methods. New NOEMA observations of CS 3─2 toward AB Aur are presented. We used velocity-integrated intensity maps to determine the inclination and position angles. Keplerian masks were constructed for all observed species to assess the presence of non-Keplerian motions. We used the CS/SO ratio to study the C/O ratio. We compared our present and previous interferometric observations of AB Aur with a NAUTILUS disk model to gain an insight into the S elemental abundance and C/O ratio. Results. We derived an observational CS/SO ratio ranging from 1.8 to 2.6. Only NAUTILUS models with C/O≳1 can reproduce such ratios. The comparison with models points to strong sulfur depletion, with [S/H]=8 × 10⁻⁸, but we note that no single model can simultaneously fit all observed species.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): IV. CO gas imaging and overview

First Author: Mac Manamon, S.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2012.1.00142.S, 2012.1.00198.S, 2015.1.01260.S, 2016.1.00104.S, 2016.1.00195.S, 2016.1.00907.S, 2017.1.00167.S, 2017.1.00825.S, 2018.1.01222.S, 2019.1.00189.S, 2022.1.00338.L
BibCode: 2026A&A...705A.198M

Context. CO gas is detected in a significant number (~20) of debris discs (exoKuiper belts), but understanding its origin and evolution remains elusive. Crucial pieces of evidence are its mass and spectro-spatial distribution, which are coupled through optical depth and have only been analysed at low to moderate resolution so far. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is the first ALMA large program to target debris discs at high spectro-spatial resolution. Aims. We used ¹²CO and ¹³CO J=3-2 line data of 18 debris belts observed by ARKS, 5 of which were already known to be gas-bearing, in order to analyse the spectro-spatial distribution of CO and constrain the gas mass in discs that were known to host gas previously, and to search for gas in the remaining 13 discs without previous CO detections. Methods. We developed a line-imaging pipeline for ARKS CO data with a high spectro-spatial resolution. Using this tool, we produced line cubes for each of the ARKS targets, with a spatial resolution down to about 70 mas and a spectral resolution of 26 m s⁻¹. We used spectro-spatial shifting and stacking techniques to produce a gallery of maps with the highest possible signal-to-noise ratio (S/N) and with radial and spectral profiles that reveal the distribution and kinematics of gas in five gas-bearing discs at unprecedented detail. Results. For each of the five gas-bearing discs (HD 9672/49 Ceti, HD 32297, HD 121617, HD 131488, and HD 131835), we constrained the inner radius of the ¹²CO (r_min ~ 3-68 au), and we found that the radial brightness profile of CO peaked interior to the dust ring, but that CO was also more radially extended than the dust. In a second-generation scenario, this would require significant shielding of CO that would allow it to viscously spread to the observed widths. We present the first radially resolved ¹²CO/¹³CO isotopologue flux ratios in five gas-bearing debris discs and found them to be constant with radius for the majority (four out of five) of systems. This indicates that ¹²CO and ¹³CO are both optically thick or optically thin throughout the discs. We report CO line fluxes or upper limits for all systems and optical depth dependant masses for the five systems with detected CO. Finally, we analysed the ¹²CO J=3-2 line luminosities for a range of ARKS debris discs and for debris discs from the literature. We confirm that gas is mostly detected in young systems. However, the high scatter seen in young/high fractional luminosity systems indicates no trend within the systems with detected gas. This could be caused by different system properties and/or evolution pathways.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): X. Interpreting the peculiar dust rings around HD 131835

First Author: Jankovic, M. R.
Instruments: ALMA_Band_6, ALMA_Band_7, SPHERE
ProgramIDs: 095.C-0298, 2012.1.00142.S, 2012.1.00198.S, 2015.1.01260.S, 2016.1.00104.S, 2016.1.00195.S, 2016.1.00907.S, 2017.1.00167.S, 2017.1.00825.S, 2018.1.01222.S, 2019.1.00189.S, 2022.1.00338.L
BibCode: 2026A&A...705A.204J

Context. Dusty discs detected around main-sequence stars are thought to be signs of planetesimal belts in which the dust distribution is shaped by collisional and dynamical processes, including interactions with gas if present. The debris disc around the young A-type star HD 131835 is composed of two dust rings at ∼65 au and ∼100 au, a third unconstrained innermost component, and a gaseous component centred at ∼65 au. New ALMA observations show that the inner of the two dust rings is brighter than the outer one, in contrast with previous observations in scattered light. Aims. We explore two scenarios that could explain these observations: the two dust rings might represent distinct planetesimal belts with different collisional properties, or only the inner ring might contain planetesimals while the outer ring consists entirely of dust that has migrated outwards due to gas drag. Methods. To explore the first scenario, we employed a state-of-the-art collisional evolution code. To test the second scenario, we used a simple dynamical model of dust grain evolution in an optically thin gaseous disc. In each case we identified the parameters of the planetesimal and the gaseous disc that best reproduce the observational constraints. Results. Collisional models of two planetesimal belts cannot fully reproduce the observations by only varying their dynamical excitation, and matching the data through a different material strength requires an extreme difference in dust composition. The gas-driven scenario can reproduce the location of the outer ring and the brightness ratio of the two rings from scattered light observations, but the resulting outer ring is too faint overall in both scattered light and sub-millimetre emission. Conclusions. The dust rings in HD 131835 could be produced from two planetesimal belts, although how these belts would attain the required extremely different properties needs to be explained. The dust-gas interaction is a plausible alternative explanation and deserves further study using a more comprehensive model.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): IX. Gas-driven origin for the continuum arc in the debris disc of HD121617

First Author: Weber, P.
Instruments: ALMA_Band_6, ALMA_Band_7, SPHERE
ProgramIDs: 0101.C-0420, 2012.1.00142.S, 2012.1.00198.S, 2015.1.01260.S, 2016.1.00104.S, 2016.1.00195.S, 2016.1.00907.S, 2017.1.00167.S, 2017.1.00825.S, 2018.1.01222.S, 2019.1.00189.S, 2022.1.00338.L
BibCode: 2026A&A...705A.203W

Context. Debris discs were long considered to be largely gas-free environments, where dynamical evolution is governed primarily by collisional fragmentation, gravitational stirring, and radiative forces. Recent detections of CO molecular line emission in debris discs demonstrate that gas is present, but its abundance and origin are still uncertain. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) observed both the gas and dust of several debris discs at high resolution and revealed a narrow ring of gas and dust in the disc HD 121617, with an asymmetric arc-like feature that is 40% brighter than the rest of the ring. Aims. An important open question is how representative the estimated CO masses are for the total gas mass in debris discs. We aim to constrain the total gas mass in HD 121617 using numerical models under the assumption that the dust arc is produced by hydrodynamical processes involving the gas. Methods. We used the hydrodynamical code Dusty FARGO-ADSG, in which dust is modelled as Lagrangian particles. We explored the effects of radiation pressure and dust feedback, as well as of varying the total gas mass on the dynamical evolution of the system. We compared these simulations with observations via radiative transfer calculations. Results. We find that an unstable gas ring can create a size-dependent radial and azimuthal dust trap. The total gas mass dictates the efficiency of particle trapping as a function of grain size. We find that two of our models, M_gas=50 M_⊕ and M_gas=5 M_⊕, can simultaneously reproduce the observed arc in the ALMA band 7 continuum image and the radial outward offset of the VLT/SPHERE scattered light ring, driven by the combined effects of gas drag and radiation pressure. We further find a conservative lower limit of M_gas>2.5 M_⊕ and a conservative upper limit of M_gas<250 M_⊕. Conclusions. If the ALMA band 7 asymmetry is caused by gas drag, reconciling the required gas mass with the observed ¹²CO emission suggests the presence of significant amounts of H₂, consistent with the gas being primordial, that is, long-lived remnant material from the protoplanetary disc phase. In this scenario, HD 121617 would represent a hybrid disc, bridging the protoplanetary and debris disc stages. As an arc-shaped emission can alternatively be reproduced by a planet's gravitational forcing, future observations are crucial to distinguish between these two scenarios.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): VII. Optically thick gas with broad CO gaussian local line profiles in the HD 121617 disc

First Author: Brennan, A.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2012.1.00142.S, 2012.1.00198.S, 2015.1.01260.S, 2016.1.00104.S, 2016.1.00195.S, 2016.1.00907.S, 2017.1.00167.S, 2017.1.00825.S, 2018.1.01222.S, 2019.1.00189.S, 2022.1.00338.L
BibCode: 2026A&A...705A.201B

Context. CO gas has been detected in ~20 debris discs, typically classified as CO-poor or CO-rich. We present observations of the CO-rich HD 121617 debris disc as part of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS). Aims. We model local CO line profiles in the HD 121617 debris disc to investigate optical depth, CO mass, and temperature. HD 121617 is a well-suited ARKS target due to its previously detected CO emission and moderate inclination, reducing the effect of Keplerian shear. Methods. Using high-resolution ALMA Band 7 observations of ¹²CO J=3─2 (26 m s⁻¹, 0_⋅'' 1), we create local line profiles by aligning and stacking spectra in concentric annuli of 0_⋅'' 02 width. These profiles are modelled with both a toy model and a RADMC-3D model that includes projection effects and Keplerian shear. Results. The resulting local profiles are Gaussian-shaped and broad due to the effect of Keplerian shear. Fitting a RADMC-3D model to the ¹³CO data, we find that an optically thick model (temperature of 38 K and mass of 2 × 10⁻³ M_⊕) reproduces the data, particularly the enhanced intensity at orbital azimuths of ~±45° and ±135°, which forms an X-shape in the velocity integrated intensity map, as well as the broader ¹²CO linewidth compared to ¹³CO. Scaling this model by the ISM abundance ratio (~77) also reproduces the ¹²CO data, but high optical depths and model assumptions limit mass constraints. Conclusions. Keplerian shear causes azimuthally averaged line profiles to appear Gaussian regardless of optical depth; therefore, we caution against using the local line profiles to distinguish between optically thin and thick emission. We constrain the mean molecular weight to 12.6_−1.1^+1.3, dependent on model assumptions. Although model dependent, our ¹³CO results indicate that C¹⁸O might also be optically thick in CO-rich debris discs, contrary to previous assumptions, and that the mean molecular weight is significantly higher than if H₂ were the dominant gas species, suggesting a non-primordial composition.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): VI. Asymmetries and offsets

First Author: Lovell, J. B.
Instruments: ALMA_Band_6, ALMA_Band_7, SPHERE
ProgramIDs: 096.C-0640, 0104.C-0436, 0102.C-0916, 095.C-0273, 0101.C-0753, 098.C-0686, 095.C-0298, 0101.C-0420, 2012.1.00142.S, 2012.1.00198.S, 2015.1.01260.S, 2016.1.00104.S, 2016.1.00195.S, 2016.1.00907.S, 2017.1.00167.S, 2017.1.00825.S, 2018.1.01222.S, 2019.1.00189.S, 2022.1.00338.L
BibCode: 2026A&A...705A.200L

Context. Asymmetries in debris discs provide unique clues to understand the evolution and architecture of planetary systems. Previous studies of debris discs at (sub)millimetre wavelengths have suggested the presence of asymmetries in a wide variety of systems, yet the lack of sufficiently sensitive high-resolution observations means that the typical properties of debris disc asymmetries have not been studied at the population level. The aim of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is to expand our understanding of radial and vertical dust structures, as well as gas distributions and kinematics, in debris discs. The ARKS sample of 24 highly resolved targets in ALMA's Bands 6 and 7 (1.1─1.4 mm and 0.8─1.1 mm, respectively) provided a unique opportunity to study their asymmetries. Aims. Here, in ARKS VI, we present a systematic analysis of the asymmetries and stellocentric offsets present in the ALMA continuum data for the ARKS survey. Our aims are to (i) identify asymmetries in debris disc dust distributions, (ii) quantify debris disc asymmetry properties, and (iii) discuss the potential origins of debris disc asymmetries. This work is the first systematic analysis of asymmetries in a large sample of well-resolved discs at (sub)millimetre wavelengths. Methods. We utilised empirical methods to identify emission asymmetries (relative to disc major and minor axes, and azimuthal disc locations) and the presence of offset emission between disc centres and the locations of the host stars, via an analysis of their calibration procedures and disc properties. We associated observational asymmetry types (offset, major and/or minor axis, azimuthal) and plausible physical classes (arcs, eccentricities, and possible clumps and warps) associated with each source. Results. We show that there are ten systems, almost half of the ARKS sample, that host either a continuum emission asymmetry or offset emission. Three systems host offsets (HD 15115, HD 32297, and HD 109573 (HR 4796)), four host azimuthal asymmetries (HD 9672 (49 Ceti), HD 92945, HD 107146, and HD 121617), two host an asymmetry in their major axis (HD 10647 (q¹ Eri), and HD 39060 (β Pic)), and one hosts an asymmetry in their minor axis (HD 61005). We attribute the offset asymmetries to non-zero eccentricities, and three of the azimuthal asymmetries to arcs. The presence of an asymmetry or offset in the ARKS sample appears to be correlated with the fractional luminosity of cold dust. We tentatively suggest that continuum asymmetries are more prevalent in CO-rich debris discs, suggesting that gas interactions may drive debris dust asymmetries. We identify seven other tentative asymmetries, including four in distinct ARKS systems and three in systems with otherwise significant asymmetries. Conclusions. This study demonstrates that debris disc asymmetries in the ARKS sample are common, and plausibly so in the wider population of debris discs at (sub)-millimetre wavelengths. This means that (sub)-millimetre asymmetries plausibly await discovery in debris discs as we probe these with higher sensitivity and resolution. Throughout, we highlight future studies to further investigate the origins of debris disc asymmetries, and build on the work presented here.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): II. The radial structure of debris discs

First Author: Han, Yinuo
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2012.1.00142.S, 2012.1.00198.S, 2015.1.01260.S, 2016.1.00104.S, 2016.1.00195.S, 2016.1.00907.S, 2017.1.00167.S, 2017.1.00825.S, 2018.1.01222.S, 2019.1.00189.S, 2022.1.00338.L
BibCode: 2026A&A...705A.196H

Context. Debris discs are populated by belts of planetesimals, whose structure carries dynamical imprints of planets and the formation and evolutionary history of the planetary system. The relatively faint emission of debris discs has previously made it challenging to obtain a large sample of high-resolution ALMA images to characterise their substructures. Aims. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) was recently completed to cover the lack of high-resolution observations and to investigate the prevalence of substructures such as radial gaps and rings in a sample of 24 debris discs. This study characterises the radial structure of debris discs in the ARKS programme. Methods. We modelled all discs with a range of non-parametric and parametric approaches, including those that deconvolve and deproject the image or fit the visibilities directly, in order to identify and quantify the disc substructures. Results. Across the sample we find that of the 24 discs, 5 host multiple rings, 7 are single rings that display halos or additional low-amplitude rings, and 12 are single rings with at most tentative evidence of additional substructures. The fractional ring widths that we measured are significantly narrower than previously derived values, and they follow a distribution similar to the fractional widths of individual rings resolved in protoplanetary discs. However, there exists a population of rings in debris discs that are significantly wider than those in protoplanetary discs. We also find that discs with steep inner edges consistent with planet sculpting tend to be found at smaller (<100 au) radii, while more radially extended discs tend to have shallower edges more consistent with collisional evolution. An overwhelming majority of discs have radial profiles that are well-described by either a double power law or double-Gaussian parametrisation. Conclusions. While our findings suggest that it may be possible for some debris discs to inherit their structures directly from pro-toplanetary discs, there exists a sizeable population of broad debris discs that cannot be explained in this way. Assuming that the distribution of millimetre dust reflects the distribution of planetesimals, mechanisms that cause rings in protoplanetary discs to migrate or debris discs to broaden soon after formation may be at play, possibly mediated by planetary migration or scattering.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): I. Motivation, sample, data reduction, and results overview

First Author: Marino, S.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2012.1.00142.S, 2012.1.00198.S, 2015.1.01260.S, 2016.1.00104.S, 2016.1.00195.S, 2016.1.00907.S, 2017.1.00167.S, 2017.1.00825.S, 2018.1.01222.S, 2019.1.00189.S, 2022.1.00338.L
BibCode: 2026A&A...705A.195M

Context. The outer regions of planetary systems host dusty debris discs analogous to the Kuiper belt (exoKuiper belts), which provide crucial constraints on planet formation and evolution processes. ALMA dust observations have revealed a great diversity in terms of radii, widths, and scale heights. At the same time, ALMA has also shown that some belts contain CO gas, whose origin and implications are still highly uncertain. Most of this progress, however, has been limited by low angular resolution observations that hinder our ability to test existing models and theories. Aims. High-resolution observations of these belts are crucial for understanding the detailed distribution of solids and for constraining the gas distribution and kinematics. Methods. We conducted the first ALMA large programme dedicated to debris discs: the ALMA survey to Resolve exoKuiper belt Substructures (ARKS). We selected the 24 most promising belts to best address our main objectives: analysing the detailed radial and vertical structure, and characterising the gas content. The data were reduced and corrected to account for several systematic effects, and then imaged. Using parametric and non-parametric models, we constrained the radial and vertical distribution of dust, as well as the presence of asymmetries. For a subset of six belts with CO gas, we constrained the gas distribution and kinematics. To interpret these observations, we used a wide range of dynamical models. Results. The first results of ARKS are presented as a series of ten papers. We discovered that up to 33% of our sample exhibits substructures in the form of multiple dusty rings that may have been inherited from their protoplanetary discs. For highly inclined belts, we found that non-Gaussian vertical distributions are common and could be indicative of multiple dynamical populations. Half of the derived scale heights are small enough to be consistent with self-stirring in low-mass belts (M_belt ≤ M_Neptune). We also found that 10 of the 24 belts present asymmetries in the form of density enhancements, eccentricities, or warps. We find that the CO gas is radially broader than the dust, but this could be an effect of optical depth. At least one system shows non-Keplerian kinematics due to strong pressure gradients, which may have triggered a vortex that trapped dust in an arc. Finally, we find evidence that the micron-sized grains may be affected by gas drag in gas-rich systems, pushing the small grains to wider orbits than the large grains. Conclusions. ARKS has revealed a great diversity of radial and vertical structures in exoKuiper belts that may arise when they are formed in protoplanetary discs or subsequently via interactions with planets and/or gas. We encourage the community to explore the reduced data and data products that we have made public through a dedicated website.

Stellar-mass black holes on the millimetre Fundamental Plane of black hole accretion

First Author: Elford, Jacob S.
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2016.1.00496.S, 2016.1.00773.S, 2017.1.00051.S, 2019.1.01324.T, 2023.1.00887.S
BibCode: 2026MNRAS.546ag037E

Recent work revealed the existence of a galaxy 'millimetre Fundamental Plane of black hole accretion', a tight correlation between nuclear 1 mm luminosity, intrinsic 2─10 keV X-ray luminosity and supermassive black hole mass, originally discovered for nearby low- and high-luminosity active galactic nuclei. Here we use mm and X-ray data of five X-ray binaries (XRBs) to demonstrate that these stellar-mass black holes also lie on the mm Fundamental Plane, as they do at radio wavelengths. One source for which we have multi-epoch observations shows evidence of deviations from the plane after a state change, suggesting that the plane only applies to XRBs in the hard state, as is true again at radio wavelengths. We show that both advection-dominated accretion flows and compact jet models predict the existence of the plane across the entire range of black hole masses, although these models vary in their ability to accurately predict the XRB black hole masses.

On the multiplicity of red-Herschel sources and its implications for extreme star formation

First Author: Quirós-Rojas, Marianela
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2016.1.00087.S, 2016.1.00139.S, 2017.1.00510.S, 2018.1.00489.S, 2018.1.00526.S, 2021.1.01628.S, 2022.1.00432.S
BibCode: 2026MNRAS.545f2133Q

We study the multiplicity of galaxies in the largest sample of red-Herschel sources (

$S_{250 \, \mu \mathrm{m}} < S_{350 \, \mu \mathrm{m}} < S_{500 \, \mu \mathrm{m}}$

) using archival Atacama Large Millimeter/submillimeter Array (ALMA) observations. Out of 2416 fields with ALMA detections (from a total of 3089 analysed maps), we identify 474 multiple systems within a radius of 16 arcsec (equivalent to the 500

$\mu$

m Herschel beam size): 420 doubles, 51 triples, and 3 quadruples. In each case, the brightest source contributes, on average, 64, 48, and 42 per cent of the total flux in double, triple, and quadruple systems. The average combined ALMA flux density of the sources in double systems is comparable to that of the two brightest components within triple and quadruple systems. Non-parametric tests suggest that only a small fraction of the double systems (

${\lesssim} 13$

per cent) are composed of sources with compatible redshifts, while 47─67 per cent of triple and quadruple fields contain at least one potentially associated pair. Simulations using a mock catalogue of dusty star-forming galaxies suggest that 32 per cent of the double systems are likely physically associated (

$\Delta z < 0.01$

, i.e.

$\lesssim$

10 cMpc at

$z = 3$

) and, while only 8 per cent of the triple and none of the quadruple systems meet this criterion,

${\sim}$

70 per cent of them include at least one likely associated pair. Our results suggest that enhanced star formation rates in submillimetre galaxies are primarily driven by internal processes rather than large-scale interactions. This study also provides a catalogue of potential overdensities for follow-up observations, offering insights into protocluster formation and evolution.

Ring Asymmetry and Spin in M87*

First Author: Bernshteyn, Vadim
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00841.V, 2019.1.01797.V
BibCode: 2026ApJ..1000..231B

Event Horizon Telescope (EHT) images of the supermassive black hole M87* depict an asymmetric ring of emission. General relativistic magnetohydrodynamic (GRMHD) models of M87* and its accretion disk predict that the amplitude and location of the ring's peak brightness asymmetry should fluctuate due to turbulence in the source plasma. We compare the observed distribution of brightness asymmetry amplitudes to the simulated distribution in GRMHD models, across varying black hole spin a_*. We show that, for strongly magnetized (MAD) models, three epochs of EHT data marginally disfavor ∣a_*∣ ≲ 0.2. This is consistent with the Blandford─Znajek model for M87's jet, which predicts that M87* should have nonzero spin. We show quantitatively how future observations could improve spin constraints and discuss how improved spin constraints could distinguish between differing jet-launching mechanisms and black hole growth scenarios.

Unveiling the collision between molecular outflows: observational evidence and hydrodynamic simulations

First Author: Cohen-Arazi, E.
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.00914.S
BibCode: 2026MNRAS.547ag071C

We present an unexplored scenario for interpreting the outflows in the EGO G338.92+0.55 (b) region (hereafter, EGO G338). Within this framework, we investigate the hypothesis that the interaction between two outflows is responsible for the observed morphology and kinematics of this astrophysical object. To explore this possibility, we reanalyse the region using observational molecular line data. We base our analysis on maps of moments 0, 1, and 2 of the CO emission associated with the molecular outflows. Additionally, we conduct three-dimensional hydrodynamic simulations to examine the presence or absence of a collision between two jets. From our numerical results, we produce synthetic CO images to facilitate a direct comparison with observations. The findings of this study provide compelling evidence that the observed morphology and kinematics in the EGO G338 region are the result of a likely collision between two molecular outflows.

ALMA Band 9 CO(6─5) Reveals a Warm Ring Structure Associated with the Embedded Protostar in the Cold Dense Core MC 27/L1521F

First Author: Tokuda, Kazuki
Instruments: ALMA_Band_6, ALMA_Band_7, ALMA_Band_9
ProgramIDs: 2011.0.00611.S, 2015.1.00340.S, 2024.1.00023.S
BibCode: 2026ApJ..1001L...1T

Infall and outflows, coupled with magnetic fields, rapidly structure the gas around newborn protostars. Shocks from interacting components encode the temperature and density distribution, offering a direct probe of the earliest evolution history. However, interferometric observations characterizing warm envelopes using high-excitation lines remain scarce. We present Atacama Large Millimeter/submillimeter Array Band 9 observations of the Taurus dense core MC 27/L1521F, which hosts a Class 0 protostar, targeting the CO(J = 6─5) line at an angular resolution of ∼2″ (≍300 au). We detect an off-centered ringlike structure with a diameter of ∼1000 au that was not identifiable in previous low-J CO data, where emission close to the systemic velocity is strongly affected by optical depth. The ring shows a typical peak brightness temperature of ∼3 K at our resolution. Excitation considerations indicate that the detected CO(J = 6─5) emission likely arises from relatively warm (T ≳ 20 K) and dense (n(H₂) ≳ 10⁵ cm⁻³) gas embedded within the surrounding cold, dense core. The morphology and kinematics suggest an energetic and localized shock-heating event, potentially linked to dynamical gas─magnetic-field interactions in the earliest protostellar phase. Our results demonstrate that high-J CO observations provide a powerful new window on warm and dense gas components, enabling a more direct view of the physical processes operating at the onset of star formation.

Disk Wind Feedback from High-mass Protostars. V. Application of Multimodal Machine Learning to Characterize Outflow Properties

First Author: Xu, Duo
Instruments: ALMA_Band_6
ProgramIDs: 2015.1.01454.S
BibCode: 2026ApJ..1001..120X

Characterizing protostellar outflows is fundamental to understanding star formation feedback, yet traditional methods are often hindered by projection effects and complex morphologies. We present a multimodal deep learning framework that jointly leverages spatial and spectral information from CO observations to infer protostellar mass, inclination, and position angle (PA). Our model, trained on synthetic Atacama Large Millimeter/submillimeter Array (ALMA) observations generated from 3D magnetohydrodynamic simulations, utilizes a cross-attention fusion mechanism to integrate morphological and kinematic features with probabilistic uncertainty estimation. Our results demonstrate that Vision Transformer architectures significantly outperform convolutional networks, showing remarkable robustness to reduced spatial resolution. Interpretability analysis reveals a physically consistent hierarchy: spatial features dominate across all parameters, whereas spectral profiles provide secondary constraints for mass and inclination. Applied to observational ALMA data, the framework delivers stable mass and PA estimates with exceptionally tightly constrained inclination angles. This study establishes multimodal deep learning as a powerful, interpretable tool for overcoming projection biases in high-mass star formation studies.

Full-polarization millimeter wavelength variability of Sagittarius A^* during the 2018 EHT campaign

First Author: Albentosa-Ruiz, Ezequiel
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00797.V
BibCode: 2026A&A...708A.179A

Context. Sagittarius A* (Sgr A^*), the supermassive black hole at the center of the Milky Way, provides a unique laboratory to study accretion dynamics and plasma processes near the event horizon. Aims. We investigated the variability and polarization properties of Sgr A^* using ALMA observations during the 2018 Event Horizon Telescope campaign. Methods. We analyzed high-cadence full-polarization light curves from ALMA at millimeter wavelengths, performed time-series analysis, and investigated the temporal behavior during an X-ray flare observed by Chandra on 2018 April 24. The variability characteristics are compared with expectations from standard accretion flow models. Results. We find low variability in total intensity (σ/μ < 10%), but significantly higher variability in linear and circular polarization (∼30% and ∼50%, respectively). A time-series analysis reveals red-noise variability, with power spectral densities between −2 and −3 across all Stokes parameters. Polarized intensity shows stable intra-day timescales, while total intensity exhibits more variable timescales, suggesting distinct emission regions, with polarization likely arising from a coherent structure. On April 24, a statistically significant inter-band delay in polarized intensity coincides with a near-simultaneous X-ray and millimeter peak that deviates from the typical delayed flare scenario. This event also features enhanced millimeter variability and coherent polarization loop evolution. The observed simultaneity challenges standard models of transient synchrotron emission with cooling delays, favoring instead a scenario of continuous energy injection in an optically thin region. Conclusions. Our results offer new constraints on the physical mechanisms driving variability in Sgr A^*, and provide key observational input for refining theoretical models of accretion and plasma behavior in the vicinity of supermassive black holes.

Warps survive beyond fly-by encounters in protoplanetary disks: RW Aur A as a case study

First Author: Kimmig, C. N.
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00973.S
BibCode: 2026A&A...708A.194K

Aims. Stellar fly-bys can have multiple dynamical effects on protoplanetary disks, including warping and the excitation of spiral arms. Since observations indicate that warps are common, we aim to investigate these effects for different fly-by trajectories. We further link our models to observations by applying them to the RW Aur system, which is a fly-by candidate with a well-constrained trajectory. Methods. We investigated the disk dynamics in grid-based hydrodynamical simulations, which allow for a lower disk viscosity than in commonly used smoothed particle hydrodynamics models. We post-processed our simulations of the RW Aur system with radiative transfer models to create synthetic images of the dust continuum and gas kinematics. Results. Fly-bys inclined with respect to the original disk plane can excite warps of a few degrees, but the exact outcome depends on the specific geometry of the encounter. Specifically, we find that the position of the periastron with respect to the initial disk plane plays a role in the resulting warp strength. Within our parameter set, the strongest warp is excited for a retrograde fly-by with a periastron that is not in the same plane as the disk. Our models show that the warp can persist even after the perturber can no longer be clearly linked to the system, implying that past fly-bys are a possible origin of observed warps. Excited spirals arms, on the other hand, are much more short-lived than a warp. We performed a simulation of the recent close encounter in the observed disk around RW Aur A, one of the few systems with a well-constrained trajectory. We find that a warp of about 5° can be excited and that the strong spiral arms have already disappeared at the current time of observation (300 yr after periastron). This compares well with existing continuum observations, and our synthetic kinematic evaluations hint at remnant structures in the gas density that may be detectable.

Multiwavelength ALMA Imaging of HD 34282: Dust-trapping Signatures of a Vortex Candidate

First Author: Ma, Xiaoyi
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2022.1.00315.S, 2015.1.00192.S, 2017.1.01578.S, 2023.1.00108.S
BibCode: 2026ApJ..1001..124M

Azimuthal arcs in millimeter continuum emission from protoplanetary disks are often attributed to dust-trapping vortices, but definitive observational confirmation of vortices remains lacking. We present sub- 0.″1 resolution Atacama Large Millimeter/submillimeter Array continuum observations of the HD 34282 disk at 0.9, 1.3, 2.1, and 3.1 mm. These observations resolve a bright azimuthal arc superposed on a compact double-gap, triple-ring morphology, most clearly at shorter wavelengths, and enable us to probe the physical origin of the arc. It exhibits a lower spectral index than the surrounding rings, consistent with enhanced grain growth and/or higher dust surface density of a dust-trapping vortex. Its azimuthal width decreases with increasing wavelength, consistent with tighter confinement of larger grains or lower optical depths at longer wavelengths. These observations probe dust with Stokes numbers St ≲ 0.03. Vortex models predict negligible peak shifts in this regime, consistent with the 1.3─3.1 mm data. At 0.9 mm; however, the arc peak is offset by ∼15^∘ ± 4^∘ in the direction of disk rotation relative to longer wavelengths, and the nearside ring emission is locally dimmer compared to the farside, likely reflecting optical-depth or temperature effects. These observations are consistent with azimuthal dust trapping, potentially associated with a vortex-induced pressure maximum.

astromorph: self-supervised machine learning pipeline for astronomical morphology analysis

First Author: Bjerkeli, P.
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00532.S
BibCode: 2026A&A...708A.156B

Context. Modern telescopes generate increasingly large and diverse datasets, often consisting of complex and morphologically rich structures. To efficiently explore such data requires automated methods that can extract and organize physically meaningful information, ideally without the need for extensive manual interaction. Aims. Our aim is to provide a user-friendly implementation of a self-supervised machine learning framework to explore morphological properties of large datasets, based on the Bootstrap Your Own Latents (BYOL) method. By enabling the generation of meaningful image embeddings without manually labelled data, the framework will enable key tasks such as clustering, anomaly detection, and similarity-based exploration. Methods. We present astromorph, a Python package that implements the BYOL method in a way tailored for astronomical imaging. In contrast to existing BYOL implementations, astromorph accommodates data of varying dimensions and resolutions, including both single-channel FITS images and multi-channel spectral cubes. The package is built with usability in mind, and offers streamlined pipeline scripts for ease of use as well as deeper customization options via PyTorch-based classes. Results. To demonstrate the utility of astromorph, we apply it in two contrasting science cases representing different astronomical domains: images of protoplanetary disks observed with the Atacama Large Millimeter/submillimeter Array (ALMA), and infrared dark clouds observed with Spitzer and Herschel. In both cases we demonstrate how astromorph produces scientifically meaningful embeddings that capture morphological differences and similarities across large samples. Conclusions. astromorph enables users to apply a robust, label-free approach for uncovering morphological patterns in astronomical datasets. The successful application to two markedly different datasets suggests that the pipeline is broadly applicable across a wide range of imaging-rich astronomical contexts, providing a user-friendly tool for advancing discovery in observational astronomy.

JOYS: JWST MIRI/MRS spectra of the inner 500 au region of the L1527 IRS bipolar outflow

First Author: Devaraj, R.
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00261.L, 2019.A.00034.S
BibCode: 2026A&A...708A..29D

Context. Outflows and jets are defining characteristics in protostellar evolution, intimately linked to accretion. Understanding their properties and origins is essential for probing the earliest phases of star formation. Aims. This study characterizes the physical and kinematic properties within the innermost 500 au region of the L1527 bipolar outflow, a class 0/I low-mass protostar, as part of the JWST Observations of Young protoStars (JOYS) program. Methods. We obtained spectroscopic observations using the JWST MIRI/MRS instrument across 5-28 μm at 0.2-1.0″ spatial resolution. We identified emission lines from molecular and ionized species and analyzed their spatial morphology using line-integrated intensity maps. We derived gas temperatures and column densities from excitation diagram analysis of H₂ rotational lines and compared results with shock models. Results. The observations reveal extended molecular hydrogen emission tracing the bipolar outflow, with the H₂ gas temperatures distributed into warm (~550 K) and hot (~2500 K) components, likely originating from moderate-velocity J -type shocks and some UV irradiation. We detect forbidden atomic and ionized emission lines of [Ni II], [Ar II], [Ne II], [Ne III], [S I], and [Fe II] showing spatially extended morphology. Double-peaked emission profiles were seen in [Ar II], [Ne III], and [Fe II] in the eastern region, suggesting that the high-velocity component traces a fast, highly ionized jet. A radial velocity map derived from [Ne II] emission shows the eastern region to be redshifted and the western region blueshifted, contrary to earlier interpretations. Conclusions. The analysis of the MIRI/MRS observations reveals molecular, atomic, and ionized emission lines in this low-mass protostar connected with active outflow signatures. The most striking feature discovered is a poorly collimated high-velocity ionized jet, embedded within a broader, wide-angle molecular outflow likely driven by a disk wind. The coexistence of these components supports a stratified outflow structure and suggests that L1527 exhibits jet-launching characteristics atypical of its early evolutionary stage.

Diverse stages of star formation in the IRAS 18162-2048 region: Emergence of UV feedback

First Author: Fedriani, R.
Instruments: ALMA_Band_3, SINFONI
ProgramIDs: 0101.C-0317, 2012.1.00441.S
BibCode: 2026A&A...708A..11F

Context. High-mass star formation remains a major open problem in astrophysics, particularly regarding the transition between deeply embedded protostars and the onset of ionising radiation capable of producing photodissociation regions (PDRs) and compact H II regions. Aims. We aim to characterise the excitation and ionisation conditions of the high-mass star-forming region IRAS 18162−2048, which is where the parsec-scale jet HH80−81 lies. Methods. We obtained adaptive optics─assisted integral field spectroscopy in the near-IR K band (1.93─2.47 µm) with VLT/SINFONI, complemented by VLA X and C bands (3−6 cm) and ALMA band 3 (∼3.3 mm) observations. We analysed the continuum and line emission to derive visual extinction and excitation conditions and the kinematics of the gas of the region. Results. The near-IR continuum reveals two IR sources, IRS 2 and IRS 7, while the main protostellar core, IRAS 18162-2048, remains undetected up to 2.47 µm. IRS 7 shows a peculiar hydrogen recombination line (HRL) Brγ profile with a narrow emission component superimposed on a broad absorption feature, consistent with a B2/B3 zero-age main-sequence (ZAMS) star. Extended H₂ emission exhibits a 'sawtooth' pattern in the excitation diagram, characteristic of UV radiation in a PDR rather than shock excitation. The radiative transfer model Cloudy reproduces the H₂ ro-vibrational populations for T_gas = 600 K and n_H = 7.9 × 10³ cm⁻³. The VLA X and C bands observations reveal a compact radio source previously reported as a 'stationary condensation' (SC) and coincident with IRS 7. For the first time, we detect IRS 7/SC in millimetre wavelengths. The spectral index in the 3−6 cm and 3.3 mm regime is consistent with optically thin free─free emission. Conclusions. Our near-IR and radio observations reveal that IRS 7/SC is a B2/B3 ZAMS star that has begun to photo-ionise its environment, giving rise to an extended PDR and a compact H II region. The coexistence of this source with the deeply embedded protostar IRAS 18162-2048 and other bubble-like structures in the field suggests a multi-generational star-forming environment. Future James Webb Space Telescope observations targeting the H₂ pure rotational lines (3─28 µm) and other HRLs less affected by extinction will be essential to characterising the cooler molecular and ionised gas to fully disclose the formation history of the region.

MUSE-ALMA Haloes: XIV. The ALMA Large Programme Data Release

First Author: Péroux, Céline
Instruments: ALMA_Band_4, ALMA_Band_6, UVES
ProgramIDs: 113.2693, 2023.1.00127.L
BibCode: 2026A&A...708A.146P

The interactions between gas and galaxies are of paramount importance to our understanding of structure formation. A fundamental element of such baryon cycle studies is a complete census of the condensed matter (stars and cold gas) in both galaxies and their immediate surroundings, the so-called circumgalactic medium. Of particular importance are the processes of converting molecular gas into stars and deciphering whether this < 100 K gas is tracing gas flows. The MUSE-ALMA Haloes survey assembled probes of the neutral atomic gas H I, ionised gas, and stellar component for a sample of 79 z ∼ 0.5 galaxies. This was achieved by combining absorption-line spectroscopy of background quasars with a projected impact parameter as low as 5 kpc and as high as 250 kpc to probe the low-density circumgalactic gas with emission-line tracers of both ionised gas and stars. This paper presents the Large Programme observational setup and releases the data characterising the molecular phase of some of the MUSE-ALMA Haloes targets so as to reach a complete census of their condensed baryons. ALMA's unique millimetre coverage and high sensitivity are ideal for characterising the CO emission of these z ∼ 0.5 H I-selected galaxies. By measuring the molecular mass, kinematics, gas flows, and gas fractions, this project (i) quantifies the role of molecular gas in H I-rich galaxies, (ii) characterises the molecular phase of gas flows from morpho-kinematics analyses, and (iii) establishes a census of the condensed baryons in the interstellar and circumgalactic media. Ultimately, these results will provide unique insights into the baryon cycle ─ a crucial component of galaxy formation.

The ALPINE-CRISTAL-JWST Survey: Chemical Abundance Comparison between the ISM and CGM of Main-sequence Galaxies at z = 4─6

First Author: Wang, Wuji
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.00428.L, 2019.1.00226.S, 2022.1.01118.S, 2021.1.00280.L
BibCode: 2026ApJ..1000..308W

Gaseous halos around galaxies play an important role in galaxy evolution. The exchange of metals from the interstellar medium (ISM) to the circumgalactic medium (CGM) is caused by the formation, feedback, and/or merging history of galaxies. We study the variation in chemical composition between the ISM (≲3 kpc) and CGM (∼5─10 kpc) for a sample of M_⋆ > 10^9.5 M_⊙ main-sequence galaxies at 4 < z < 6 with both JWST and Atacama Large Millimeter/submillimeter Array observations. Using JWST/NIRSpec integral field spectroscopy, we derive the optical line ratios from the ISM and the CGM for our sample, focusing on the typical optical lines used for metallicity studies. Our comparison shows that the ISM and the CGM have similar chemical abundances. This indicates that the CGM of these typical 4 < z < 6 galaxies is enriched to the level of their ISM in the early Universe. Using statistical tests, we find that some of the line ratios show marginal differences between the ISM and CGM. Combined with Cloudy modeling, our results suggest that a difference in ionization level (higher for the ISM) is the dominant reason for the observed ratio difference of oxygen line ratios. There is also indication of a deficit in the nitrogen abundance with respect to oxygen in the CGM, which suggests a delay in redistribution of secondary nitrogen. Finally, an enhanced F_{[C II]158μm}/F_Hα ratio is observed in the CGM, suggesting that feedback and/or mergers play a key role in metal mixing.

A Potential Link between Nuclear Winds and Cold Gas Outflows on Kiloparsec Scales in Reionization-era Quasars

First Author: Zhu, Yongda
Instruments: ALMA_Band_7
ProgramIDs: 2022.1.00662.S
BibCode: 2026ApJ..1000..312Z

Feedback from accreting supermassive black holes may regulate galaxy evolution, but statistical evidence linking nuclear winds to kiloparsec-scale cold gas outflows remains limited in the early Universe. Here, we report statistical evidence for such a connection in a sample of luminous quasars at z ∼ 5.5. We compare stacked [C II] 158 μm emission profiles from Atacama Large Millimeter/submillimeter Array observations, which trace galactic-scale neutral gas, for quasars with and without broad absorption lines (BALs) that indicate powerful nuclear winds on subkiloparsec scales. A total of 5 BAL and 11 non-BAL quasar spectra are included in the stacking analysis. The BAL quasar stack exhibits a potential blueshifted broad component in the [C II] line profile, with a velocity offset of ∆v_b = −2.1 × 10² km s⁻¹ and a full width at half-maximum of 1.18 × 10³ km s⁻¹, whereas the non-BAL stack shows no obvious broad component. Using a conservative "clean-stack" selection that excludes quasars with partial [C II] spectral coverage, the BAL broad residual is reduced to a hint-level feature. We estimate that up to a few percent to one quarter of the nuclear wind energy may be transferred to cold neutral gas on kiloparsec scales. Although the sample size is limited, these results suggest a potential link between BAL winds and cold gas feedback in quasar host galaxies. These results provide empirical motivation for future tests of how multiphase outflows relate to the diversity of quasar host properties, including M_BH/M_*.

Substellar initial mass function of Trumpler 14

First Author: Rom, T.
Instruments: VIRCAM
ProgramIDs: 088.C-0117
BibCode: 2026A&A...706A..58R

Context. Young, massive stellar clusters offer a prime setting to explore brown dwarf (BD) formation under high densities and intense UV radiation. Trumpler 14 (Tr 14), a ∼1 Myr old cluster located at a distance of 2.4 kpc that is particularly rich in O-type stars, is an ideal target for such a study. Aims. Our goal is to measure the initial mass function (IMF) in the young massive, high-UV-flux cluster. Methods. We present the deepest study to date of the IMF in Tr 14, based on Gemini Multi-Conjugate Adaptive Optics System/Gemini-South Adaptive Optics Imager imaging. We constructed the IMF using both the Besançon Galactic model and an observational control field from VISTA for background correction. Completeness was assessed using artificial star tests and applied to the IMF derivation. Results. We estimated the IMF down to the 20% completeness limit found at ∼0.01 M_⊙. Using the control-field-based IMF as our primary result, we find a slope of α = 0.14 ± 0.19 for masses between 0.01 and 0.2 M_⊙, and α = 1.72 ± 0.04 for 0.2─4.5 M_⊙, where dN/dM ∝ M^−α. The low-mass slope is largely influenced by the incompleteness-affected lowest bin; excluding it brings our results into agreement with those for other young clusters. The resulting median for the star-to-BD ratio in the 0.03─1 M_⊙ mass range is 4.0, with a 95% confidence interval of 2.8─5.8. Conclusions. Our analysis reveals that Tr 14 hosts a relatively flat substellar IMF, but this is strongly influenced by the lowest-mass bin, which may be affected by incompleteness. When that bin is excluded, the IMF becomes consistent with those of other regions. The star-to-BD ratio falls within the usually observed ∼3─6 range, indicating that BDs with masses above ∼0.03 M_⊙ form with similar efficiencies across environments. However, the relative lack of objects below this threshold suggests that the presence of an environment with both high stellar density and far-UV flux plays a role in shaping the IMF by suppressing the formation of BDs at masses <0.03 M_⊙.

Multicolor Characterization of Optically Invisible FU Orionis-type Outbursts: Demonstration and Prospects for the WINTER Survey

First Author: Frostig, Danielle
Instruments: VIRCAM
ProgramIDs: 179.B-2002
BibCode: 2026ApJ...997..263F

Episodic mass accretion is the dominant mechanism for mass assembly in the protostellar phase. Although prior optical time-domain searches have allowed detailed studies of individual outbursts, these searches remain insensitive to the earliest stages of star formation. In this paper, we present the characterization of two FU Orionis (FUor) outbursts identified using the combination of the ground-based, near-infrared Wide-field Infrared Transient Explorer (WINTER) and the space-based, mid-infrared NEOWISE survey. Supplemented with near-infrared spectroscopic follow-up, we show that both objects are bona fide FUor type outbursts based on (i) their proximity to star-forming regions, (ii) large amplitude (2─4 magnitudes) infrared brightening over the last decade, (iii) progenitor colors consistent with embedded (Class I) protostars, and (iv) "mixed-temperature" infrared spectra exhibiting characteristic signatures of cool outer envelopes and a hot inner disk with a wind. While one source, WNTR24-cua, is a known FUor that we independently recover; the second source, WNTR24-egv, is a newly confirmed object. Neither source is detected in contemporaneous ground-based optical imaging, despite flux limits ≳100× fainter than their infrared brightness, demonstrating the capabilities of WINTER to identify heavily obscured young stellar object outbursts. We highlight the capabilities of the Galactic Plane Survey of the recently commissioned WINTER observatory in addressing the poorly understood FUor population with its unique combination of real-time detection capabilities, multicolor sensitivity, weekly cadence, and wide area coverage.

The Milky Way Project: Bridging Intermediate- and High-mass Star Formation with the MIRION Catalog of Yellowballs

First Author: Devine, Kathryn
Instruments: SHFI
ProgramIDs: 193.C-0584, 092.F-9315, Chilean data, Max-Planck data
BibCode: 2026ApJ...998..132D

We describe the construction and use of the Mid-InfraRed Interstellar Objects and Nebulae (MIRION) catalog, which was compiled from 6176 objects identified as "yellowballs" (YBs) by participants in the Milky Way Project. The majority of YBs are compact photodissociation regions generated by intermediate- and high-mass young stellar objects that are embedded in star-forming clumps ranging in mass from 10 to 10⁶ M_⊙ and luminosity from 10 to 10⁴ L_⊙. The MIRION catalog increases the number of candidate intermediate-mass star-forming regions (SFRs) by nearly 2 orders of magnitude, providing an extensive database with which to explore the transition from isolated low-mass to clustered high-mass star formation. The catalog comprises five tables that include mid- and far-infrared photometry, velocities of source-associated molecular clouds, distances to these molecular clouds, physical properties of source-associated star-forming clumps, and source crossmatches with other catalogs. The structure of the catalog enables users to easily sort objects for further study based on distance or environmental properties. Our preliminary analysis extends our earlier findings that indicate a relationship between infrared (IR) colors and the physical properties and evolutionary stages of SFRs. Photometry will be periodically updated online to incorporate measurements from volunteers participating in a classroom activity known as the People Enabling Research: a Yellowball Survey of the Colors Of Protostellar Environments (or PERYSCOPE) project. These updates will continue to refine the IR flux measurements and reduce photometric errors. A follow-up paper will present a detailed analysis of how IR colors can be used to predict the properties of star-forming environments.

Dense Molecular Clumps with Large Blue Asymmetries: Evidence for Collapse

First Author: Jackson, James M.
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: 2026ApJ...998..167J

An analysis of the Millimetre Astronomy Legacy Team 90 GHz survey has produced a sample of 27 candidate dense molecular clumps with large collapse motions, as revealed by large "blue" asymmetrical line profiles of the optically thick HCO⁺ (1─0) line. New, more sensitive molecular line observations of this sample, conducted with the Mopra 22 m telescope, confirm the blue asymmetries in the HCO⁺ (1─0) line profiles, with large, positive values of the asymmetry parameter A ( ĀHCO+=0.69±0.01 ), and positive, but smaller asymmetries in the HCN (1─0) and HNC (1─0) lines ( ĀHCN=0.35±0.01 and ĀHNC=0.28±0.01 ), as expected for a less optically thick tracer in collapsing clumps. The small, positive mean asymmetry parameters for C₂H (N = 1─0; J = 3/2─1/2; F = 2─1) and H¹³CO⁺ (1─0), ĀC2H=0.15±0.02 and ĀH13CO+=0.18±0.03 , likely indicate slightly optically thick emission for at least some clumps. The hyperfine ratios for N₂H⁺ (1─0) are in their optically thin, LTE, values, but for HCN (1─0) they are not; the F = 1 → 1 hyperfine line shows abnormally weak intensities. A simple two-component model shows that self-absorption of the background F = 1 → 1 hyperfine line by the main F = 2 → 1 hyperfine line of a cold, foreground, redshifted cloud can reproduce the observed HCN (1─0) hyperfine intensities and match the HCN (1─0) and HCO⁺ (1─0) line profiles. All of these results are consistent with self-absorption of the optically thick lines on the red side of the profile, as expected for collapsing clumps. The simple two-cloud model suggests that this sample represents dense clumps with extreme collapse velocities, V_inf ∼ 2.4 km s⁻¹.

Distinguishing ram pressure from gravitational interactions: Applying the size-shape difference method to real galaxies

First Author: Lassen, Augusto E.
Instruments: MUSE
ProgramIDs: 196.B-0578
BibCode: 2026A&A...706A..85L

Context. In dense environments, mechanisms such as ram pressure stripping (RPS) and gravitational interactions can induce the formation of similar morphological features in galaxies that are only distinguishable through a detailed study of the stellar properties. While RPS affects recently formed stars through the displacement of the gas disk from which they are formed, gravitational interactions perturb stars in a similar way. Aims. We present the first observational test of the size-shape difference (SSD) measure. This novel approach, which was originally designed and validated for simulated galaxies, quantifies morphological differences between young and intermediate-age stellar populations to distinguish RPS from gravitationally interacting galaxies. Methods. We analyzed 67 galaxies from the GASP survey using spatially resolved star formation history derived from the SINOPSIS spectral fitting code. In our fiducial model, we compared stellar populations in two age bins (t < 20 Myr and 20 Myr ≤ t < 570 Myr) to calculate SSD values. The sample includes confirmed cases of RPS with different stripping intensities, as well as undisturbed and gravitationally interacting galaxies. Results. We find that the extreme cases of RPS show SSD values ∼3.5× higher than undisturbed and gravitationally interacting galaxies ( 56 − 15 + 24 as compared to 16 − 2 + 6 and 16 − 3 + 6 , respectively), which confirms simulation predictions. This enhancement reflects RPS-induced asymmetries: the youngest stars are either compressed along the leading edge or displaced into extended tails of cold gas from which they are formed (or both), while older populations remain undisturbed. In contrast, gravitational interactions perturb all stars uniformly, producing lower SSD values. Conclusions. Size-shape difference robustly distinguishes strong RPS cases, even when different age bins are used. This holds even without correcting for disk inclination, or when single-band imaging are used to trace stellar distributions. This makes SSD a promising tool to select RPS candidates for spectroscopic follow-up in upcoming large-scale surveys.

Galaxy Protoclusters as Drivers of Cosmic Reionization: I. Bubble Overlap at Redshift z ∼ 7 in LAGER-z7OD1

First Author: Martin, Crystal L.
Instruments: VIRCAM
ProgramIDs: 179.A-2005, 198.A-2003, 110.25A2, 1104.A-0643, 284.A-5026
BibCode: 2026ApJ...997..102M

Since the launch of JWST, the sample size of reionization-era Lyα emitters (LAEs) has been steadily growing; yet inferences about the neutral hydrogen fraction in the intergalactic medium exhibit increasing variance at redshift z ≍ 7, possibly indicating significant field-to-field fluctuations in the progression of cosmic reionization. In this paper, we present new JWST/NIRSpec and Keck/LRIS spectra of nine LAEs in the redshift z ∼ 7 protocluster LAGER-z7OD1. Measurements of Lyα transmission and Lyα velocity offset along multiple sight lines map the Lyα damping wing optical depth across the galaxy overdensity. In the standard context of inside-out ionization, we estimate the radii of ionized bubbles, Rimin=0.07− 0.69 Mpc (physical), based on the distance from each LAE to the first neutral patch along the sight line. The resulting 3D topology reveals three distinct subclusters where the ionized bubbles are approaching overlap. Five of the nine LAEs plausibly ionized their bubbles, where a few bursts of star formation and a modest escape fraction are sufficient. We demonstrate, however, that the actual ionized volumes are likely larger, at least Riism = 0.42─1.29 Mpc (physical), based on an empirical model for interstellar attenuation of Lyα. Modeling galactic attenuation of Lyα significantly increases the inferred intergalactic transmission (thus enlarging the ionized path length). The error bars on the reddening correction allow fully overlapping bubbles, and our results are consistent with accelerated reionization in the protocluster.

EROS light-curve database

First Author: Afonso, C.
Instruments: Decomm.Inst.
ProgramIDs: unknownID
BibCode: 2026A&A...706A.189A

Context. The project called Expérience de Recherche d'Objets Sombres (EROS) carried out photometric surveys of dense stellar fields toward the Magellanic Clouds (LMC and SMC), the Galactic bulge and Galactic spiral arms in the period 1990-2003. The main goal of the experiment was to search for the Galactic dark matter in the form of massive compact objects (machos) through the gravitational microlensing effect. Aims. The historical record of the flux variations in the monitored stars by EROS-2 will be a unique asset for time-domain astronomy and to complement current and future searches of transient sources. Methods. We describe the set of light curves that was obtained with the EROS-2 program from 1996 to 2003, when more than 86 million stars were monitored. The set is publicly released through the Centre de Données de Strasbourg (CDS). This dataset includes 28.7 and 4.0 million light curves in the LMC and SMC, 42.9 million light curves in the Galactic bulge, and 10.4 million light curves toward the Galactic spiral arms and has several hundred measurements for each object. The data from EROS-1 are also being released. Results. The object catalog, light curves, and images are accessible through the CDS portal. This is useful for determining the past behavior of newly discovered variable objects.

Calcium in a supernova remnant as a fingerprint of a sub-Chandrasekhar-mass explosion

First Author: Das, Priyam
Instruments: MUSE
ProgramIDs: 0104.D-0104
BibCode: 2025NatAs...9.1356D

Type Ia supernovae play a fundamental role as cosmological probes of dark energy and produce more than half of the iron in our Galaxy. Despite their central importance, a comprehensive understanding of their progenitor systems and triggering mechanism is still a long-standing fundamental problem. Here we present high-resolution integral field spectroscopic observations of the young supernova remnant SNR 0509-67.5 in the Large Magellanic Cloud. We uncover a double-shell morphology of highly ionized calcium [Ca XV] and a single shell of sulphur [S XII], observed in the reverse shocked ejecta. Our analysis reveals that the outer calcium shell originates from the helium detonation at the base of the outer envelope, while the inner shell is associated with the carbon-oxygen core detonation. This morphological distribution of intermediate-mass elements agrees qualitatively with the predicted signature of the double detonation of a sub-Chandrasekhar-mass white dwarf from a hydrodynamical explosion simulation. Our observations reveal two distinct, spatially separated peaks in surface brightness of [Ca XV] from the supernova remnant phase, providing substantial evidence that sub-Chandrasekhar-mass explosions through the double-detonation mechanism could occur in nature. They also highlight the importance of remnant tomography in understanding explosion mechanisms from the remnant phase.

EPISODE. III. The Nested Jet/Outflow Morphology of EC 53 Revealed by JWST and ALMA

First Author: Lee, Seonjae
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2016.1.01304.T, 2019.1.01792.S, 2022.1.00800.S
BibCode: 2026ApJ..1000...83L

We present an extensive study of the structure and kinematics of the jet and outflow of EC 53, a Class I protostar with a quasiperiodic variability, using combined James Webb Space Telescope (JWST) and Atacama Large Millimeter/submillimeter Array (ALMA) observations. ALMA continuum observations resolve a compact disk with a radius of ∼0 .″ 14 (60 au). Scattered light from the outflow cavity is prominent in the short-wavelength NIRCam and NIRSpec observations, revealing only the southeast nearside lobe. We detect 27 H₂ emission lines tracing a narrow cone-shaped structure within the outflow cavity. A high-velocity ionized jet is detected in several forbidden atomic lines, characterized by a position angle of 142^∘, an opening angle of 1 .° 4, and an estimated geometric launching radius of at most ∼40 au. Mid-IR CO rovibrational emission lines, stronger in the P-branch, show a similar distribution to the H₂ emission and are likely to originate from hot gas within the outflow cavity. CO and C₂H emission lines detected by ALMA trace slower, colder outflow components and cavity walls. The spatial and kinematic stratification between the hot atomic and molecular components and the colder molecular gas is consistent with predictions from MHD disk wind models, although envelope material entrained by a wide-angle wind or jet may also contribute. Our analysis highlights the powerful synergy between JWST and ALMA in advancing the understanding of protostellar jets and outflows across multiple spatial and physical scales.

exoALMA. XXI. The Morphology and Dynamics of Vertical Flows

First Author: Benisty, Myriam
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.01123.L
BibCode: 2026ApJ..1000L..14B

Vertical gas flows—such as winds and meridional circulations—are natural outcomes of protoplanetary disk processes and play a critical role in the earliest stages of planet formation. We analyze the vertical gas motions in 14 disks, as part of the exoALMA Large Program, focusing on the ¹²CO J = 3─2 and ¹³CO J = 3─2 emission lines. Using DISCMINER to model the Keplerian velocity field, we extract line-of-sight velocity residuals and measure the radial and vertical components of the gas motion. Vertical motions are detected in most disks. Two types of patterns emerge: (1) oscillatory up/down flows, likely linked to instabilities; and (2) transitions from downward to upward motions that we interpret as the bases of disk winds. In most cases, the velocity amplitudes are of a few tens of m s⁻¹. However, two disks, MWC758 and CQ Tau, show two spiral velocity features in their residual maps, red- and blueshifted, which we interpret as vertical velocities reaching up to ∼350 m s⁻¹ (∼0.7c_s), consistent with the gas motion in eccentric disks. Fast upward motions (up to 500 m s⁻¹; ∼1.8c_s) are also detected in the outer disk of MWC758. Synthetic observations from (magneto)hydrodynamic simulations validate the reliability of our method. Although strong molecular winds appear to be relatively rare in ¹²CO and ¹³CO, our study shows that, when traced by deep high-spectral-resolution line data, protoplanetary disks exhibit ubiquitous vertical flows. However, their overall velocity structure is highly complex, preventing the identification of a coherent dominant physical mechanism driving the vertical motions across all disks, thus requiring further theoretical investigation.

High-z [OI] emission lines: COLDSIM simulations and ALMA observations

First Author: Parente, M.
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.00265.S, 2023.1.01450.S
BibCode: 2026A&A...705A..39P

Neutral-oxygen [OI] far-infrared emission lines at 63 μm and 145 μm are powerful probes of the physical conditions in the interstellar medium, although they have not been fully exploited in high-redshift studies.

ACES: The Magnetic Field in Large Filaments in the Galactic Center

First Author: Paré, Dylan M.
Instruments: ALMA_Band_3
ProgramIDs: 2021.1.00172.L
BibCode: 2026ApJ..1000...37P

The Galactic center (GC) is an extreme region of the Milky Way that is host to a complex set of thermal and nonthermal structures. In particular, the GC contains high-density gas and dust that is collectively referred to as the Central Molecular Zone (CMZ). In this work, we study a subset of HNCO filaments identified in Band 3 Atacama Large Millimeter/submillimeter Array (ALMA) observations of the GC obtained by the ALMA CMZ Exploration Survey that are comparable to high-density filaments identified in the Galactic disk. We compare the orientation of the magnetic field derived from 214 μm Stratospheric Observatory for Infrared Astronomy and 850 μm James Clerk Maxwell Telescope observations with the filament orientation to determine which mechanisms dominate the formation of these filaments. We observe a large range of magnetic orientations in our observed filaments indicating the complex environments the filaments are located in. We also compare the observational results to synthetic datasets created using an MHD model of the GC. Our analysis reveals that the dominant mechanisms local to the HNCO filaments vary throughout the GC with some filaments being dominated by supersonic turbulence and others by subsonic turbulence. The comparison to synthetic observations indicates that the observed filaments are in magnetically dominated environments that could be supporting these filaments against collapse. Our results on the CMZ filaments are also compared to results obtained on similar filaments located in the Galactic disk, and we find that the filaments studied here are possible CMZ analogs to the dense filamentary "bones" observed previously in the Galactic disk.

Featureless stars: flux calibration for extremely large telescopes

First Author: Cooke, Ryan J.
Instruments: XSHOOTER
ProgramIDs: 111.24LB
BibCode: 2026MNRAS.546f2246C

The spectrophotometric flux calibration of recent spectroscopic surveys has reached a limiting systematic precision of approximately

$1-3$

per cent, and is often biased near the wavelengths associated with H I Balmer absorption. As we prepare for the next generation of imaging and spectroscopic surveys, and high-precision cosmology experiments, we must find a way to address this systematic. Towards this goal, we have identified a global network of 29 bright (

$G< 17.5$

) featureless white dwarf stars that have a spectral energy distribution consistent with an almost pure blackbody form over the entire optical and near-infrared wavelength range. Based on this sample, we have computed the systematic uncertainty and AB magnitude offsets associated with Gaia, SDSS, SMSS, Pan-STARRS, DES, and 2MASS, and we have also checked the consistency of our objects with both GALEX and WISE. The magnitude range of the featureless stars reported here are ideally suited to observations taken with the forthcoming generation of extremely large telescopes, as well as calibrating the survey data acquired by the Rubin, Euclid, and Roman observatories. Finally, all of the high-precision spectrophotometric standard stars reported here have been included in the latest release of the PYPEIT data reduction pipeline.

E-XQR-30: evidence for an increase in the ionization state of metal absorbers from z ∼ 6 to z ∼ 2

First Author: Rowlands, Stephanie
Instruments: XSHOOTER
ProgramIDs: 0102.A-0154, 0102.A-0478, 084.A-0360, 087.A-0607, 088.A-0897, 098.B-0537, 1103.A-0817, 294.A-5031, 60.A-9024, 096.A-0095, 096.A-0418, 097.B-1070, 086.A-0574, 086.A-0162, 085.A-0299, 084.A-0390, 084.A-0550, 0101.B-0272, 0100.A-0625
BibCode: 2026MNRAS.546f2254R

We investigate the evolution of the ionization state of metal-enriched gas in and around galaxies near the epoch of reionization using a sample of 488 metal absorption systems at 4.3

$\lesssim z \lesssim$

6.3 from the E-XQR-30 survey. We classify the absorption systems based on whether they display only low-ionization absorption (C II, Si II, Mg II), only high-ionization absorption (C IV, Si IV), or both. The percentage of low-ionization-only systems decreases from 24 per cent at

$z\sim$

6 to 2 per cent at

$z\sim$

4.3, whilst the fraction of high-ionization-only systems increases from 52 per cent to 82 per cent. For mixed absorbers (with both low and high ionization absorption), we use the column density ratios log(N_{C II}/N_{C IV}) and log(N_{Si II}/N_{Si IV}) to quantify the average ionization as a function of redshift. The log(N_{Si II}/N_{Si IV}) ratio does not change significantly over 5

$\lesssim z \lesssim$

6.3. We combine the E-XQR-30 log(N_{C II}/N_{C IV}) measurements with literature measurements at

$z\sim$

2─4 and find that the log(N_{C II}/N_{C IV}) ratio declines by a factor of

$\sim$

20 between

$z\sim$

6 and

$z\sim$

2. To explore possible drivers of this evolution, we run photoionization models of gas slabs illuminated by a uniform ultraviolet (UV) background at fixed density, metallicity, and H I column density. We find that the increase in the ionization state of metal absorbers towards lower redshifts can likely be explained by some combination of (1) an increase in the metallicity of C IV-absorbing gas and (2) a decrease in the typical H I column densities of the absorbing gas, driven by the declining cosmic mean density and a rapid rise in the strength of the UV background during the final stages of reionization.

JWST Exoplanetary Worlds and Elemental Survey (JEWELS). I. High-precision Chemical Abundances of 20 FGK Planet-hosting Stars from JWST Cycle 2

First Author: Sun, Qinghui
Instruments: ESPRESSO, HARPS, UVES
ProgramIDs: 106.21QM, 192.C-0224, 099.C-0491, 0102.D-0789, 198.C-0169, 084.C-1039, 099.C-0303, 1102.C-0923, 0103.C-0874, 082.C-0040, 0103.C-0422, 0102.C-0493, 097.C-0863, 095.D-0383, 0102.D-0185, 089.D-0202, 112.25T7, 111.24HZ, 112.25T4, 105.20KD, 106.21BV
BibCode: 2026ApJS..282...37S

We present high-precision chemical abundances for 20 FGK stars hosting planets observed in JWST Cycle 2 GO programs. Using high-resolution, high-signal-to-noise ratio spectra from the ESO and Keck archives, we perform a strict line-by-line differential analysis relative to the Sun to derive stellar parameters and abundances of 19 elements from C to Zn. The stars span effective temperatures of 4500─6500 K and metallicities from −0.57 to +0.50 dex. The sample includes hosts of both gas giants and terrestrial planets, allowing direct comparison between stellar composition and planetary properties. Several of the giant planets orbit metal-rich stars. The detailed abundance patterns show clear chemical diversity, including carbon-enhanced but mildly metal-poor stars (TOI-824, TOI-561, TOI-1130, GJ 9827) and α-enhanced metal-poor stars (TOI-561, GJ 9827, TOI-824). These variations trace differences in protoplanetary disk composition and may influence planetary interiors and atmospheric chemistry. The planet hosts show a range of [C/O] ratios, and the diverse [Mg/Si] ratios may suggest varied interior compositions for their rocky planets. This homogeneous stellar abundance, together with future uniform JWST planetary atmosphere measurements, provides a foundation for exploring the planet mass─metallicity relation and the connection between stellar chemistry and planetary formation pathways. These results constitute the first step in a larger survey spanning multiple JWST cycles to systematically examine how host star composition shapes exoplanetary systems.

Abundance of Heavy r-process Elements in CEMP-rs Stars: The Role of the i-process

First Author: Riyas, A. M.
Instruments: UVES
ProgramIDs: 105.20LJ, 076.D-0451, 078.D-0217
BibCode: 2026ApJ...997...44R

Carbon-enhanced metal-poor (CEMP) stars are ancient stars enriched in carbon and heavy elements. Some of these stars exhibit enhanced s-process and/or r-process elements, and hence are classified as CEMP-s, CEMP-rs, or CEMP-r. This classification is challenging due to the limited availability of heavy element abundances, particularly among r-process elements. Heavy r-process elements such as terbium, holmium, thulium, ytterbium, lutetium, tantalum, and iridium have rarely been measured because their sensitive lines are located in the ultraviolet. However, they provide sensitive diagnostics of the s-, r-, and i- nucleosynthetic processes. In this work, we aim to obtain a secure classification of CEMP-s and -rs stars and investigate whether the i-process can account for the measured abundance patterns in CEMP-rs stars. We derive the abundance profiles, notably for 12 heavy r-elements, including, in some cases, tantalum, using high-resolution UVES spectra of 17 CEMP-s and -rs stars. Based on indicators such as the [s/r] abundance ratio or the model-independent "abundance distance", nine stars are confirmed as CEMP-rs and six as CEMP-s. The classification of two objects remains uncertain. The i-process satisfactorily reproduces the abundance patterns of CEMP-rs stars. However, larger samples are needed to confirm trends with metallicity and clarify how CEMP-rs stars differ from CEMP-s stars.

Secondary Standards in the UKIRT Faint Standard Fields

First Author: Górski, Marek
Instruments: SOFI
ProgramIDs: 190.D-0237, 095.D-0424, 092.D-0295, 090.D-0409, 084.D-0591, 094.D-0056, 099.D-0307, 0102.D-0590, 084.D-0640, 097.D-0151, 088.D-0447, 088.D-0401, 0102.D-0469, 096.D-0170, 092.D-0349, 082.D-0513
BibCode: 2026ApJS..282...44G

We present precise J- and K-band photometric measurements for 128 near-infrared (NIR) secondary standard stars, located in the 19 United Kingdom Infrared Telescope/Maunakea Observatories (UKIRT/MKO) primary faint standard fields. The data were collected over more than 50 nights, covering a decade of observations between 2008 and 2018 at the ESO La Silla Observatory, using the New Technology Telescope equipped with the SOFI NIR camera. Presented magnitudes are calibrated onto the MKO photometric system. The J- and K-band magnitudes range from 10 to 15.8 mag, with median values of J∼ = 13.5 mag and K∼ = 13 mag. The selection process ensured high photometric quality, with a precision better than 0.01 mag for all stars. The catalog excludes stars with close neighbors, high proper motion, or variable stars. Using these fields for standardization can improve the precision and accuracy of photometric calibrations without increasing the observational time cost.

ExoJAX Retrievals of VLT/CRIRES Spectra of Luhman 16AB: C/O Ratios and Systematic Uncertainties

First Author: Yama, Hibiki
Instruments: CRIRES
ProgramIDs: 291.C-5006
BibCode: 2026ApJ...997..118Y

We present atmospheric retrievals of the benchmark brown dwarf binary Luhman 16AB using high-resolution VLT/CRIRES spectra and the differentiable framework ExoJAX. We derive elemental abundances and temperature─pressure (T─P) profiles while explicitly testing the robustness of the results against major sources of systematic uncertainty. We first perform retrievals with a power-law T─P profile and assess the sensitivity of inferred molecular abundances and C/O ratios to different CO line lists (ExoMol, HITEMP with air- and H2-broadening). We then introduce a flexible Gaussian process-based T─P profile, allowing a nonparametric characterization of the thermal structure and a more conservative treatment of uncertainties. For both components, we infer C/O ratios of about 0.67, slightly above solar, with line list systematics at the 7% level emerging as the dominant source of uncertainty, whereas assumptions about T─P parameterization or photometric variability play a lesser role. The retrieved T─P profiles and molecular abundances are broadly consistent with atmospheric models and equilibrium chemistry. Our results establish Luhman 16AB as a key anchor for substellar C/O measurements, demonstrate the utility of flexible T─P modeling in high-resolution retrievals, and highlight the importance of systematic tests—particularly line list uncertainties—for robust comparisons between brown dwarfs and giant exoplanets.

Interferometric view into RT Pav's long secondary period: Binary versus oscillatory convective modes

First Author: Courtney-Barrer, B.
Instruments: GRAVITY, MATISSE, PIONIER
ProgramIDs: 109.23K5
BibCode: 2026A&A...705A.187C

Context. Long secondary periods (LSPs) occur in roughly one third of evolved stars, yet their origin remains uncertain. Two leading hypotheses are oscillatory convective modes and a binary companion enshrouded in dust. Aims. We investigate the LSP in the red giant RT Pav using multiwavelength interferometry to test these competing hypotheses. Methods. Observations of RT Pav were obtained with the VLTI instruments PIONIER, GRAVITY, and MATISSE spanning 1.5─5.0 μm, near the expected phase of maximum projected separation under a binary hypothesis. These data were complemented by photometric data and Gaia DR3 astrometry to constrain companion mass, orbital geometry, and photometric amplitude. Monte Carlo simulations evaluated expected interferometric signatures under both scenarios. Parametric models, including uniform-disk, limb-darkened, uniform-ellipse, binary, and oscillatory convective dipole representations, were fitted to squared-visibility and closure-phase data, informing image reconstructions. Results. Gaia constrains any potential companion to a mass whose Roche-lobe volume is smaller than the minimum extent required by the observed photometric modulation, implying that any obscuring or scattering region capable of producing the observed variability would lie beyond the gravitationally bound zone of such a companion. Binary models often return the lowest χ_ν², yet fitted positions are not consistent across wavelength, closure phases do not increase with wavelength as a dusty companion would predict, and we only find significant (> 3σ) detections occurring in two of the four tested instrumental wavebands, which is inconsistent with a coherent companion signal. Furthermore simulations and theoretical estimates indicate that a companion with a ∼1% flux ratio, at LSP-consistent separations should be consistently detectable (near or above our 3σ limits) for standard O-rich asymptotic giant branch (AGB) dust via scattering and/or thermal emission, which is not found. Conversely, an oscillatory convective dipole with a ∼200 K temperature contrast reproduces the H band morphology and the visible light-curve amplitude without violating Gaia or photometric constraints. Finally, significant short wavelength companion signals are completely removed when fitting the residuals of the best fit dipole model. Conclusions. Our interferometric snapshot of RT Pav, acquired near the phase of maximum projected separation under the binary hypothesis, supports oscillatory convective modes as the most physically consistent explanation for its LSP. A logical next step will be time-resolved spectro-interferometric monitoring across the LSP cycle.

ALMAGAL: VI. The spatial distribution of dense cores during the evolution of cluster-forming massive clumps

First Author: Schisano, E.
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00195.L
BibCode: 2026A&A...707A.221S

Context. High-mass stars and star clusters form from the fragmentation of massive dense clumps driven by gravity, turbulence, and magnetic fields. The extent to which each of these agents impacts the fragmentation depending on the clump mass, density, and evolutionary stage is still largely unknown. Aims. The ALMA evolutionary study of high-mass protocluster formation in the GALaxy (ALMAGAL) project, with ∼1000 clumps observed at ∼1000 au resolution, allows a statistically significant characterization of the fragmentation process over a large range of clump physical parameters and evolutionary stages. Our goal is to characterize where and how the dense cores revealed by ALMA are distributed in massive potentially cluster-forming clumps to trace how fragmentation is initially set and how it proceeds before gas dispersal due to stellar feedback. Methods. We characterized the spatial distribution of dense cores in the 514 ALMAGAL clumps that host at least four cores, using a set of quantitative descriptors that we evaluated against the clump bolometric luminosity-to-mass ratio, which we adopted as an indicator of the evolution of the system. We measured the separations between cores with the minimum spanning tree (MST) method, which we compared with the predictions of gravitational fragmentation from Jeans theory. We investigated whether cores have specific arrangements using the Q parameter or variations due to their masses with the mass segregation ratio, Λ_MSR. Results. ALMAGAL cores are distributed throughout the entire area of the clump, usually arranged in elliptical groups with an axis ratio e ∼2.2, although high values with e ≥ 5 are also observed. We found a single characteristic core separation per clump in ∼76% of cases, suggesting that multiple fragmentation lengths may be frequently present. Typical core separations are compatible with the clump-averaged thermal Jeans length, λ_J^th. However, we found an additional population of cores, typical of low-fragmented and young clumps, which are on average more widely separated with l ≍ 3 × λ_J^th. By stacking the distributions of the core separations in clumps of similar evolutionary stage, we also found that the separation decreases on average from l ∼22 000 au in younger systems to l ∼7000 au in more evolved ones. The ALMAGAL cores are typically distributed in fractal-type subclusters, while centrally concentrated patterns appear only at later stages, but we do not observe a progressive transition between these configurations with evolution. Finally, we also found 110 ALMAGAL systems with a signature of mass segregation, with an occurrence that increases with evolution.

Investigating the Nested Structure of the Outflow from the Low Luminosity Protostar IRAS 16253-2429 Using JWST and ALMA

First Author: Narang, Mayank
Instruments: ALMA_Band_6
ProgramIDs: 2019.A.00034.S, 2019.1.00261.L
BibCode: 2026ApJ..1000..184N

Understanding the earliest stage of star and planet formation requires detailed observations to address the connection and interplay between the accretion, outflow, and disk evolution. We present results from the observations of the low luminosity (L_bol ∼ 0.2 L_⊙) and mass (M_* ∼ 0.15 M_⊙) Class 0 protostar IRAS 16253−2429, conducted as part of the eDisk Atacama Large Millimeter/submillimeter Array (ALMA) large program and the JWST cycle-1 GO Investigating Protostellar Accretion program. Observations reveal a wide hourglass-shaped continuum cavity traced in scattered light (at ≤5 μm), with a brighter, extended northern side. We detect 15 pure rotational H₂ transitions (E_up: 1015─21411 K), revealing a wide-angle molecular outflow. The outflow width (as traced in H₂ 0─0 S(11)) at the protostellar location measures ≤35 au, slightly larger than the dust and Keplerian disk diameters (∼30 au) but wider than the 20─23 au jet width in [Fe II]. The opening angle narrows from 40° to 35° for the low-J H₂ lines (up to S(5)) and the cold gas component (ALMA ¹²CO) to ∼28°─19° for the high-J H₂ lines (S(7)─S(11)). Position─velocity diagrams of H₂ reveal higher velocities for higher E_up, ranging from 12.5 km s⁻¹ for H₂ 0─0 S(1) and S(2) to 28.5 km s⁻¹ for H₂ 0─0 S(5) and S(7) with respect to the mean flow velocity. The nested excitation and velocity structure of the collimated jet and wide-angle wind suggest a magnetohydrodynamic wind as a likely launching mechanism, similar to the findings in other protostars and Class II sources. The lower velocity millimeter CO may be gas from the infalling envelope accelerated outwards by the wide-angle wind along the cavity walls.

Benchmarking pre-main sequence stellar evolutionary tracks using disk-based dynamical stellar masses

First Author: Zallio, Luigi
Instruments: ALMA_Band_6, ALMA_Band_7, XSHOOTER
ProgramIDs: 115.27XL, 113.26NN, 097.C-0378, 105.2082, 0101.C-0866, 2013.1.00395.S, 2018.1.00564.S, 2012.1.00688.S, 2011.0.00526.S
BibCode: 2026A&A...708L...1Z

Stellar masses are a fundamental property to understand models of pre-main sequence evolution, but their values derived from Hertzsprung─Russell (HR) diagrams are strongly model dependent. We benchmark pre-main sequence stellar evolutionary tracks using stellar masses dynamically estimated by fitting a parametric model to ALMA observations of the ¹²CO (J = 3 − 2) line transition emitted by the disks orbiting 20 sources in the old (4 − 14 Myr) Upper Scorpius star forming region. We derive stellar masses from HR diagram fitting for ten different stellar evolutionary models, which we then compare with their stellar dynamical masses for comparison in the stellar mass range 0.1 − 1.3 M_⊙. Models with a moderate-to-low fraction of cold stellar spots (f = 17%) most accurately reproduce the dynamical stellar masses (100% of the targets agree within ±1σ). While a higher spot coverage (f = 34%) provides similar stellar mass predictions similar to magnetic equipartition models, larger fractions (f ≥ 51%) significantly disagree with dynamical masses. Magnetic equipartition models overestimate stellar masses up to a factor ∼20%, whereas non-magnetic models underestimate them up to ∼12%. For some models, there is evidence that the stellar mass discrepancies are anticorrelated with dynamical stellar masses. When stellar dynamical mass priors are considered in HR diagram fitting, the median age of a single source can change up to ∼25%, while the median ages inferred across different tracks become consistent, with the age scatter decreasing by ≳77%. These results provide strong empirical constraints for testing and developing evolutionary models of pre-main sequence stars.

WISDOM Project ─ XXVII. Giant molecular clouds of the lenticular galaxy NGC 1387: similarities with spiral galaxy clouds

First Author: Liang, Fu-Heng
Instruments: ALMA_Band_6, MUSE
ProgramIDs: 296.B-5054, 2016.1.00437.S, 2016.2.00053.S
BibCode: 2026MNRAS.547ag221L

Molecular gas is crucial to understanding star formation and galaxy evolution, but the giant molecular clouds (GMCs) of early-type galaxies (ETGs) have rarely been studied. Here, we present analyses of the spatially resolved GMCs of the lenticular galaxy NGC 1387, exploiting high spatial resolution (

$0.15\ \mathrm{ arcsec}$

or 14 pc)

$^{12}$

CO(2-1) line observations from the Atacama Large Millimeter/submillimeter Array. We identify 1285 individual GMCs and measure the fundamental properties (radius, velocity dispersion, and molecular gas mass) of each with a modified version of the CPROPStoo package. Unusually for an ETG, the GMCs of NGC 1387 follow scaling relations very similar to those of the Milky Way disc and Local Group galaxy clouds, and most are virialized. GMCs with large masses and radii and/or small galactocentric distances have their angular momenta aligned with the large-scale galactic rotation, while other GMCs do not. These results show that ETGs have more diversified GMC properties than previously thought. We discuss potential reasons for such diversity, and viewing-angle dependency is a plausible candidate.

MIRACLE: II. Unveiling the multiphase gas interplay in the circumnuclear region of NGC 1365 via multicloud modeling

First Author: Ceci, M.
Instruments: ALMA_Band_7, MUSE
ProgramIDs: 094.B-0321, 2016.1.00296.S
BibCode: 2026A&A...707A.376C

We present a multiphase analysis of the gas in the circumnuclear region (∼0.9 × 0.9 kpc²) of the nearby barred Seyfert 1.8 galaxy NGC 1365, observed as part of the Mid-IR Activity of Circumnuclear Line Emission (MIRACLE) program. Specifically, we combined spatially resolved spectroscopic data from JWST/MIRI, VLT/MUSE, and ALMA to provide a multiphase characterization of the ionized atomic and the warm and cold molecular gas phases. MIRI data enabled the detection of more than 40 mid-IR emission lines from ionized or warm molecular gas. Moment maps show that both cold and warm molecular gas trace the circumnuclear ring, following the rotation of the stellar disk. The ionized gas exhibits flux distributions and kinematics that vary depending on the ionization potential (IP). Low-IP species (≤25 eV) mainly trace the rotating disk, while higher-IP species (up to ∼120 eV) trace the outflowing gas. Both [O III] λ5007 Å and [Ne V] λ14 μm trace the nuclear outflow cone toward the southeast. In addition, the [Ne V] λ14 μm line traces the counter-cone of the outflow to the northwest, which is obscured in the optical at these circumnuclear scales, and is thus undetected in [O III] λ5007 Å. Unlike optical diagnostics, spatially resolved mid-IR diagnostics reveal the key role of the active galactic nucleus (AGN) as the source of gas ionization in the central region. We derived the electron density from the [Ne V] λ24 μm/[Ne V] λ14 μm line ratio, finding a median value of (750 ± 440) cm⁻³, consistent with previous estimates obtained from the optical [S II] doublet. Lastly, we applied, for the first time, a fully self-consistent combination of state-of-the-art photoionization and kinematic models (HOMERUN + MOKA^3D) to estimate the intrinsic physical outflow properties, kinematics, and energetics ─ overcoming the limitations of classical methods based on oversimplified assumptions. Exploiting the unprecedented synergy between JWST/MIRI and VLT/MUSE, HOMERUN allows us to simultaneously reproduce the fluxes of over 60 emission lines spanning from the optical to the mid-IR. This unique approach enables us to disentangle the physical conditions of AGN- and star formation-dominated components and robustly estimate the mass of the outflowing gas and other physical properties.

Young system development in a cometary globule: An investigation into the eccentric disk around AT Pyx^* in terms of planet formation and interaction with its surrounding environment

First Author: McLachlan, D.
Instruments: ALMA_Band_6, ESPRESSO, SPHERE, XSHOOTER
ProgramIDs: 111.24UB, 112.25B7, 099.C-0147, 112.25BZ, 2021.1.01705.S
BibCode: 2026A&A...707A.379M

Context. To understand the formation of planetary systems, it is necessary to observe and study systems at different evolutionary stages and in different environments. This paper presents new data and analyses of the AT Pyx system, a disk-hosting young star located in a cometary globule in the Gum Nebula. This radiation-driven structure is an unusual environment for observations of planet formation, and differs greatly from the low-mass star-forming regions disks are most commonly observed in. Aims. Aided by a collection of visual and spectroscopic data available for this system, our aim is to infer the possibility of embedded planets existing within the disk and how the system's environment may affect its disk morphology. Methods. Using data from the VLT's instruments XSHOOTER, ESPRESSO, and most prominently SPHERE, along with data from ALMA, we made a variety of measurements (geometric, photometric, and otherwise) to characterise the observed disk features and attributes such as spiral arms and eccentricity. Mapping of the velocity components was also undertaken using the ALMA gas line data to characterise disk orientation and determine the likelihood that the system is experiencing a late-stage infall event. Results. The disk is measured to have a position angle of 28.06 ± 0.02^° and an inclination of 42.5 ± 0.5^°. The disk is found to be eccentric with measured e ≍ 0.626 when deprojected. Under the assumption that the formation of a planet is wholly responsible for the primary and secondary spiral arms, we find the mass of such a planet can range between 0.004 and 3 Jupiter masses. Measurements of the velocities associated with nearby globule cloud material return reasonable velocities for a late-stage infall event. We estimate the far-ultraviolet (FUV) field strength at AT Pyx's location to be low in comparison to other surveyed disks. We also find that AT Pyx is possibly a binary system. Conclusions. AT Pyx is the first disk within a cometary globule to be spatially resolved, and is now the first such disk to be investigated to this extent. The work of this paper could potentially be a first step into the further study of disks in the moderate FUV environment of the Gum Nebula and its globules.

ALMA Band 1 observations of the ρ Oph W filament: I. Enhanced power from excess microwave emission at high spatial frequencies

First Author: Casassus, S.
Instruments: ALMA_Band_1
ProgramIDs: 2023.1.00265.S
BibCode: 2026A&A...707A.255C

Context. The ρ Oph W photo-dissociation region (PDR) is an example source of bright excess microwave emission (EME), over synchrotron, free-free, and the Rayleigh-Jeans tail of the sub-millimetre (sub-mm) dust continuum. Its filamentary morphology follows roughly that of the IR poly-cyclic aromatic hydrocarbon (PAHs) bands. The EME signal in ρ Oph W drops abruptly above ~30GHz and its spectrum can be interpreted in terms of electric-dipole radiation from spinning dust grains (or 'spinning dust'). Aims. Deep and high-fidelity imaging and spectroscopy of ρ Oph W may reveal the detailed morphology of the EME signal, free from imaging priors, while also enabling a search for fine structure in its spectrum. The same observations may constrain the spectral index of the high-frequency drop. Methods. An ALMA Band 1 mosaic yields a deep deconvolved image of the filament at 36-44 GHz, which we used as template for the extraction of a spectrum via cross-correlation in the uv plane. Simulations and cross-correlations on near-infrared ancillary data yield estimates of flux loss and biases. Results. The spectrum is a power law, with no detectable fine structure. It follows a spectral index α = −0.78 ± 0.05, in frequency, with some variations along the filament. Interestingly, the Band 1 power at high spatial frequencies increases relative to that of the IR signal, with a factor of two more power in Band 1 at ~20" than at ~100 " (relative to IRAC 3.6 μm). An extreme example of such radio-only structures is a compact EME source, without an IR counterpart. It is embedded in strong and filamentary Band 1 signal, while the IRAC maps are smooth in the same region. We provide multi-frequency intensity estimates for spectral modelling.

Observations of the temporal evolution of Saturn's stratosphere following the Great Storm of 2010─2011: II. Latitudinal distribution of CO and stratospheric winds

First Author: Cavalié, T.
Instruments: ALMA_Band_6
ProgramIDs: 2011.0.00808.S
BibCode: 2026A&A...707A.240C

Context. Saturn's Great Storm of 2010─2011 has produced two stratospheric hot spots, the "beacons," that eventually merged to produce a gigantic one in April and May 2011. This beacon perturbed stratospheric temperatures, hydrocarbon, and water abundances for several years. Aims. We aim to assess whether the beacon induced any perturbation in another oxygen species, namely CO. A second goal is to measure how the vortex perturbed the stratospheric wind regime. Methods. We conducted interferometric observations of Saturn in the submillimeter range with SMA and ALMA to spatially resolve the CO (J=3─2) and (J=2─1) emissions, respectively. We used a previously determined CO vertical profile as a template, to search for (i) the meridional distribution of CO and (ii) variations of the CO abundance associated with the storm. The high spatial and spectral resolutions of the ALMA observations enabled us to retrieve the winds from the Doppler shifts induced by the winds on the lines. Results. Despite limitations resulting from the removal of baseline ripples, we find a relatively constant meridional distribution of CO. The average CO mole fraction implied by the adopted and rescaled 220-year-old-comet-impact vertical profile is (1.7±0.7)×10⁻⁷ at 0.3 mbar, i.e., where the contribution functions peak. We also find that the CO abundance has not been noticeably altered in the beacon. The winds measured at 1 mbar show striking differences with those measured in 2018, after the demise of the beacon. We find the signature of the vortex as an anticyclonic feature. The equatorial prograde jet is 100─200 m s⁻¹ slower, and broader in latitude, than in quiescent conditions. We also detect several prograde jets in the southern hemisphere. Finally, we detect a retrograde jet at 74°N which could be a polar jet caused by the interaction of the Saturn magnetosphere with its atmosphere. Conclusions. With Saturn's equinox season approaching, new wind measurements would enable the findings presented in this paper to be confirmed by probing the two hemispheres equally and searching for a southern retrograde polar jet.

The Polarization and Magnetic Field of the Radio Arc as Observed by ALMA at 100 GHz

First Author: Salem, Nora
Instruments: ALMA_Band_3
ProgramIDs: 2024.1.00515.S
BibCode: 2026ApJ..1000..129S

The unique Galactic center nonthermal filaments (NTFs) have been a focus of investigations for over 40 yr. The most prominent manifestation of the NTFs is a bundle of parallel filaments known as the Radio Arc. Radio polarimetric observations made with the Very Large Array (VLA) at 10 GHz have revealed an alternating magnetic field pattern in the Radio Arc that could either be a result of multiple field systems being encountered along the line of sight or an intrinsic feature of the Radio Arc. These VLA observations were not able to distinguish between these possibilities due to the large rotation measures encountered toward the source. We present Atacama Large Millimeter/submillimeter Array (ALMA) 100 GHz observations of the Radio Arc that are not impacted by significant Faraday effects. The observations reported here represent both the first time that ALMA has been used to study the NTFs and the first time 100 GHz polarimetric observations have been conducted on the Radio Arc. We find a uniformly rotated magnetic field with respect to the NTF filament orientation, with the angle of rotation being constant along the length of each filament. However, we find a systematically different magnetic field orientation in different Radio Arc filaments. We use this field pattern to update our understanding of the line-of-sight structures local to the Radio Arc. We find that the magnetic field inferred from our ALMA observations is likely a result either of confusion from multiple magnetic field systems or because the polarization is centrally concentrated within the NTF filaments.

First Determination of the Cosmic Microwave Background Radiation Temperature at z = 0.68 Using Molecular Absorption Lines

First Author: Kotani, Tatsuya
Instruments: ALMA_Band_3, ALMA_Band_4
ProgramIDs: 2016.1.00031.S
BibCode: 2026ApJ..1000..141K

We analyzed millimeter-wave data toward the quasar B0218+357 observed with the Atacama Large Millimeter/submillimeter Array and obtained absorption spectra of the J = 2─1 and J = 3─2 rotational transitions of HCN, HCO⁺, HNC, H¹³CN, and H¹³CO⁺ at the cosmological redshift of z = 0.68. For HCN, HCO⁺, and HNC, we identified two distinct absorption components that are common to both transitions, whereas a single component was detected in the isotopologue spectra. In this paper, we accurately evaluate the excitation temperatures and their uncertainties from the absorption strengths of these components and use them to determine the cosmic microwave background radiation (CMB) temperature. Uncertainties in the continuum covering factor were propagated into the excitation temperature via Monte Carlo sampling. We further corrected the observed optical depths for biases due to column-density nonuniformity by assuming a lognormal column-density distribution. Under the assumption that the rotational levels are in radiative equilibrium with the CMB, we derived excitation temperature profiles in the optically thin regime. Because the excitation of HCO⁺ is biased by an additional velocity component and partial collisional excitation, this species was excluded from the final determination of the CMB temperature. From a weighted mean of the excitation temperatures obtained from HCN and HNC, we determined the CMB temperature at z = 0.68 to be 4.50 ± 0.17 K. This constitutes the first measurement of the CMB temperature at z = 0.68 based on a quasar absorption line system and represents the most precise determination at this redshift, highly consistent with the standard Big Bang cosmological model.

The GUAPOS project: VII. Physical structure and molecular environment of the G31.41+0.31 HII region

First Author: Cesaroni, R.
Instruments: ALMA_Band_3
ProgramIDs: 2017.1.00501.S
BibCode: 2026A&A...707A.327C

Context. Ionised regions around OB-type stars, formed at an early stage of their evolution, are important in the investigation of the formation processes of these objects. Thus far, however, only a few observations of their physical structure and interaction with the parental molecular cloud have been carried out. The high resolution and high sensitivity of new instruments such as ALMA and the upgraded VLA allow us to fill in this knowledge gap. Aims. We investigate the well-known core-halo ultracompact HII region G31.41+0.31 and the surrounding molecular clump to determine the density and temperature of both the ionised and neutral gas, and to possibly obtain a 3D picture of their spacial distribution. Methods. We took advantage of the full-band frequency coverage at 3 mm obtained with ALMA for the GUAPOS project to image the emission of a plethora of hydrogen recombination lines towards the G31.41+0.31 HII region, as well as several molecular transitions that serve as tracers of medium-density (~10⁴−10⁶ cm⁻³) gas. The line data are complemented by continuum measurements obtained with the VLA at 1 cm and 7 mm. By fitting these lines with a model that takes into account non-local thermal equilibrium (NLTE) effects, we were able to investigate the density and temperature structure and the velocity field of the region. Results. Our findings, based on a model fit accounting for NLTE effects, indicate that the electron temperature of the HII region mostly spans a range between 5000 and 6000 K, while the density varies between 2500 and 7500 cm⁻³. All in all, the distribution of these parameters, along with the corresponding velocity field hint at a cometary shaped HII region expanding away from the observer to the NW. The molecular gas appears to be still infalling towards the peak of the UC HII region, while its density and temperature are consistent with pressure confinement of the ionised gas to the SE.

Low Dust Mass and High Star Formation Efficiency at z > 12 from Deep ALMA Observations

First Author: Mitsuhashi, Ikki
Instruments: ALMA_Band_6, ALMA_Band_8
ProgramIDs: 2021.A.00020.S, 2023.A.00017.S, 2023.A.00037.S
BibCode: 2026ApJ..1000..159M

We investigate the dust mass buildup and star formation efficiency of two galaxies at z > 12—GHZ2 and GS-z14-0—by combining Atacama Large Millimeter/submillimeter Array and JWST observations with an analytical model that assumes dust at thermal equilibrium. We obtained 3σ constraints on the dust mass of logMdust/M⊙<5.0 and <5.3, respectively. These constraints are in tension with a high dust condensation efficiency in stellar ejecta but are consistent with models with a short metal accretion timescale at z > 12. Given the young stellar ages of these galaxies (t_age ∼ 10 Myr), dust grain growth via accretion may still be ineffective at this stage, though it likely works efficiently to produce significant dust in galaxies at z ∼ 7. The star formation efficiencies, defined as the star formation rate divided by the molecular gas mass, reach ∼10 Gyr⁻¹ over a 10 Myr timescale, aligning with the expected redshift evolution of "starburst" galaxies with efficiencies that are ∼0.5─1 dex higher than those in main-sequence galaxies. This starburst phase seems to be common in UV-bright galaxies at z > 12 and is likely associated with the unique conditions of the early phases of galaxy formation, such as bursty star formation. Direct observations of molecular gas tracers like [C II] will be crucial to further understanding the nature of bright galaxies at z > 12.

Active Galactic Nucleus Feedback and the Development of Dusty Multiphase Gas in X-Ray Emitting Elliptical Galaxies

First Author: Temi, Pasquale
Instruments: ALMA_Band_6
ProgramIDs: 2011.0.00735.S, 2015.1.00860.S
BibCode: 2026ApJ..1000..144T

This paper investigates the physical and kinematic properties of dust-rich regions in a small sample of group-centered elliptical galaxies, emphasizing their connection with the hot X-ray emitting gas and detailed dust grain characteristics. Comprehensive multiwavelength data—including Hα and CO emission detected by Multi Unit Spectroscopic Explorer and Atacama Large Millimeter/submillimeter Array—demonstrate the presence of dust clouds embedded within complex, hot X-ray atmospheres shaped by active galactic nucleus (AGN) feedback. X-ray images show bubbles and cavities surrounded by bright rims. We find that dust regions containing molecular gas traced by CO are preferentially located at the rims of these X-ray cavities, suggesting that AGN-driven outflows enhance the condensation of cold, dusty gas at these compressive interfaces. Kinematic measurements indicate that molecular and ionized gas phases are dynamically and spatially linked, supporting the framework of a multiphase medium arising from the top-down condensation rain in the hot plasma and related chaotic cold accretion. Crucially, spatial variations in the total-to-selective extinction ratio R_V show that regions where dust, CO, and Hα emission coincide exhibit notably smaller R_V values, implying steeper extinction curves and the predominance of smaller or less evolved dust grains within these mixed-phase environments. This contrasts with larger R_V values found elsewhere in the dust clouds, suggesting grain growth or survival mechanisms within shielded cold gas.

The ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). XIII. Core Mass Function, Lifetime, and Growth of Prestellar Cores

First Author: Morii, Kaho
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00192.S, 2017.1.00716.S, 2015.1.01539.S
BibCode: 2026ApJ...997..155M

The core mass function (CMF) of prestellar cores is essential for understanding the initial conditions of star and cluster formation. However, the universality of the CMF and its relationship to the initial mass function (IMF) remain unclear. We study the CMF in the earliest stage of high-mass star formation using 461 prestellar core candidates and 254 protostellar cores as a part of the ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). We find that prestellar core candidates tend to have lower masses than protostellar cores. We also find that the lifetime of prestellar cores is several times longer than the freefall time, although it approaches the freefall time as the core mass increases. The CMF, including both protostellar and prestellar cores, has a power-law slope of −2.05 ± 0.04, shallower than Salpeter's IMF slope of −2.35. Conversely, the CMF of gravitationally bound, prestellar cores has a steeper slope (−2.32 ± 0.30), indistinguishable from Salpeter's slope. This finding is consistent with observations in both low-mass star-forming regions and high-mass protoclusters, implying a universal core formation mechanism. The protostellar CMF with a larger maximum core mass can be reproduced by the prestellar CMF when an external gas infall is considered. The inferred mass infall rate is higher than the Bondi─Hoyle─Lyttleton accretion rate and follows a shallower mass dependence (smaller power-law index), more consistent with the tidal-lobe accretion. This may contribute to the evolution of CMFs seen in later stages.

CH₃OH and HCN in Interstellar Comet 3I/ATLAS Mapped with the ALMA Atacama Compact Array: Distinct Outgassing Behaviors and a Remarkably High CH₃OH/HCN Production Rate Ratio

First Author: Roth, Nathan X.
Instruments: ALMA_Band_7
ProgramIDs: 2024.1.00137.T, 2024.1.00477.T, 2024.A.00049.S
BibCode: 2026ApJ...999L..32R

We report the detection of methanol (CH₃OH) toward interstellar comet 3I/ATLAS using the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array (ALMA) on UT 2025 August 28, September 18 and 22, and October 1 and of hydrogen cyanide (HCN) on September 12 and 15. These observations spanned pre-perihelion heliocentric distances (r_H) of 2.6─1.7 au. The molecules showed outgassing patterns distinct from one another, with HCN production being depleted in the sunward hemisphere of the coma, whereas CH₃OH was enhanced in that direction. Statistical analysis of molecular scale lengths in 3I/ATLAS indicated that CH₃OH included production from coma sources at L_p > 258 km at 99% confidence. However, low signal-to-noise ratio (S/N) on long baselines, which sample emission on small spatial scales closest to the nucleus, prevented definitively ruling out CH₃OH as purely a parent species. In contrast, HCN production was indistinguishable from direct nucleus sublimation. The CH₃OH production rate increased sharply from August through October, including an uptick near the inner edge of the H₂O sublimation zone at r_H = 2 au. Compared to comets measured to date at radio wavelengths, the derived CH₃OH/HCN ratios in 3I/ATLAS of 124−34+30 and 79−14+11 on September 12 and 15, respectively, are among the most enriched values measured in any comet, surpassed only by anomalous solar system comet C/2016 R2 (Pan-STARRS).

exoALMA. XX. Tomographic Detection of Embedded Planets in Protoplanetary Disks

First Author: Izquierdo, Andrés F.
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.01123.L
BibCode: 2026ApJ..1000L..13I

The exoALMA Large Program has revealed a wealth of substructures in the dust and molecular line emission of several protoplanetary discs, suggesting that planet formation may unfold within highly dynamic environments. Using synthetic observations of planet─disk interactions and disk instabilities, we demonstrate how the origin of these substructures can be investigated through a tomographic study of molecular lines, extending the scope of the analysis beyond line-centroid kinematics alone. Our results indicate that with only a few hours of ALMA integration at moderate angular resolution ( 0.″15−0.″30 ), it is possible to identify the key signatures driven by planets more massive than 0.1% of the stellar mass. These signatures manifest not only as deviations from Keplerian motion but also as localized line broadening, enabling accurate constraints on the orbital radius and azimuthal location of the planets. We further show that a diagnostic based on line skewness in spectrally resolved observations can help distinguish between planetary and instability-driven signatures, owing to the distinct degrees of velocity coherence associated with each mechanism. Finally, we apply this tomographic analysis to exoALMA CO line data for the disks of HD 135344B and MWC 758. In HD 135344B, we identify strongly localized velocity and line-width perturbations, suggesting the possibility of three massive planets embedded in the disk: one at R = 95 au, exterior to the continuum substructures, and two within dust gaps at R = 41 au and R = 73 au. For MWC 758, the dominance of vertical-velocity spirals over localized signatures is consistent with predictions from models of moderate disk eccentricities or warps, potentially induced by a substellar companion in the inner regions of the system.

exoALMA. XXIII. Estimating Disk and Planet Properties from Dust Morphologies with DBNets 2.0

First Author: Ruzza, Alessandro
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.01123.L
BibCode: 2026ApJ..1000L..16R

The exoALMA large program provided an unprecedented view of the morphologies and kinematics of 15 circumstellar disks, offering a biased but homogenous and well-characterized sample for population-level analysis. Continuum observations revealed numerous dust substructures, known to be potential signatures of embedded planets. We analyze the observed dust morphologies with the simulation-based inference tool DBNets2.0, assuming these are due to embedded planets at fixed locations, to infer the system's properties. We estimate the putative planet mass, the disk α viscosity, scale height, and dust Stokes number that would reproduce 19 substructures in 13 of the 15 exoALMA disks. We compare our results with literature estimates derived with different methods, and find good agreement in most cases. We further explore the implications of the inferred disk properties for accretion, showing that for the Herbig stars in our sample, the implied viscous accretion timescales are too long to account for their observed stellar accretion rates. Regarding planet migration, our results favor inward migration, with only three putative planets expected to migrate outward. Finally, we check for correlations of the inferred disk and planet properties with the disks' gas-to-dust mass ratio, nonaxisymmetry index, and masses of the gas, dust, and host stars, finding no remarkable trends.

exoALMA XXII: A Two-dimensional Atlas of Deviations from Keplerian Disks

First Author: Fukagawa, Misato
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.01123.L
BibCode: 2026ApJ..1000L..15F

Protoplanetary disks are the birthplaces of planetary systems, and deviations from Keplerian rotation imprinted in disk gas kinematics serve as key tracers of physical processes and the presence of protoplanets within disks. Using the CO (J = 3─2) data from the exoALMA Large Program, encompassing 15 disks, we constructed two-dimensional (2D) maps of centroid velocity, line width, and peak intensity, and extracted non-Keplerian deviations by subtracting smooth Keplerian models. This Letter provides the first systematic and uniform overview of 2D gas substructures across the entire exoALMA sample. We find that all targets exhibit large-scale deviations from smooth Keplerian disks, displaying a variety of morphologies, including spiral-like structures, arc- or ring-like features, and patterns indicative of variations in the emitting surface height. Nonaxisymmetric spiral-arm features are detected or suggested in five disks (CQ Tau, MWC 758, HD 135344B, HD 34282, and SY Cha), and are preferentially found in Herbig Ae/Fe systems. In contrast, some other sources (J1852, PDS 66, and V4046 Sgr), despite exhibiting noticeable deviations, appear to be dynamically quieter. This 2D atlas suggests that kinematic substructures are ubiquitous in large (≳100 au) protoplanetary disks with ages of a few million years, based on the observations obtained with sufficient sensitivity at a moderate-to-high spatial resolution of ∼20 au and high-velocity resolution of ∼0.1 km s⁻¹.

ALMA Observations of Cold Methanol Gas in the Large Magellanic Cloud: N79 South Giant Molecular Cloud

First Author: Mondal, Suman Kumar
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2017.1.01323.S, 2018.1.01366.S, 2019.1.01770.S
BibCode: 2026ApJ...998..277M

We report Atacama Large Millimeter/submillimeter Array continuum and molecular line observations at 0.1 pc resolution toward the super star cluster (SSC) candidate H72.97−69.39 in the N79 region of the LMC. The continuum emission has a sharp peak around the SSC candidate but is also widely distributed. We identify two continuum sources at the northern (N79S-1) and northwestern (N79S-2) positions of the SSC continuum peak, associated with CH₃OH emission. In addition to CH₃OH, we also detect H₂CO, H₂CS, CS, SO, CO, CN, and CCH at the positions of N79S-1 and N79S-2. The rotation diagram analysis of CH₃OH and SO lines yields an average gas temperature of 13 ± 0.4 K for N79S-1 and 15 ± 0.9 K for N79S-2. Most emission lines exhibit line widths of less than 2.8 km s⁻¹, consistent with emissions from cold, dense molecular cloud cores. The abundance of cold CH₃OH gas is estimated to be (2.1 ± 1.1) × 10⁻⁹ at N79S-1 and (4.5 ± 2.5) × 10⁻¹⁰ at N79S-2. Despite the lower metallicity in the LMC, the CH₃OH abundance at N79S-1 is comparable to that of similar cold sources in our Galaxy. However, the formation of organic molecules is inhibited throughout the N79 regions, as can be seen in the nondetection of CH₃OH in most of the regions. The two positions N79S-1 and N79S-2 would be exceptional positions, where CH₃OH production is efficient. The possible origins of cold CH₃OH gas in these dense cores are discussed, along with a possible explanation for the nondetection of CH₃OH in the SSC candidate.

An observational study of rotation and binarity of Galactic O-type runaway stars

First Author: Carretero-Castrillo, M.
Instruments: FEROS
ProgramIDs: unknownID
BibCode: 2026A&A...705A.215C

Context.Gaia Data Release 3 (DR3) has revealed new massive runaway stars and large spectroscopic surveys have now enable detailed characterization studies. However, the relative contributions of binary supernova (BSS) and dynamical ejection (DES) scenarios to explain their runaway origin remain poorly constrained, particularly in the Milky Way. Aims. We aim to characterize the largest sample of Galactic O-type runaway stars ever investigated through their kinematics, rotation, and binarity with the ultimate objective of shedding light on their potential runaway origins. Methods. We used the GOSC-Gaia DR3 catalog of normal and runaway stars, along with IACOB spectroscopic information to build a sample with 214 O-type stars with information on the projected rotational velocities (v sin i). We also built a subsample of 168 O-type stars with additional information about their likely single (LS) or single-lined (SB1) spectroscopic binary nature. We also considered an additional sample of 65 double-lined (SB2) spectroscopic binaries. Results. We find that among our sample of Galactic O-type runaways, most (74%) have v sin i < 200 km s⁻¹, whereas for normal stars this fraction is slightly higher (82%). There are no fast-moving ( V PEC 2 D > 85 km s⁻¹) runaways that have been shown to be fast rotators (v sin i ≥ 200 km s⁻¹), except for HD 124 979. Runaways exhibit lower SB1 fractions than normal stars, with no runaway SB1 fast-rotating systems; on average, runaways rotate faster than normal stars; and their runaway fraction is higher among fast rotators (44%) versus the slow rotators (34%). This is consistent with BSS dominance for fast rotators. We also found that SB2 systems hardly reach runaway velocities with a low runaway fraction (10%). Runaways with V PEC 2 D > 60 km s⁻¹ are mostly single and interpreted as DES products, while runaways with V PEC 2 D > 85 km s⁻¹ are also interpreted as two-step products, with the binary V479 Sct/LS 5039 a likely example. Finally, we found that three of 12 runaway SB1 systems are high-mass X-ray binaries. Conclusions. Our observational study reveals that Galactic O-type runaways are dominated by slow rotators. The study points to a dominance of BSS among fast-rotating runaways and of DES and the two-step scenario among the high-velocity ones. The observed trends provide valuable constraints on models on the origins of runaway stars.

Observational evidence for a possible link between PAH emission and dust trap locations in protoplanetary disks

First Author: van der Marel, Nienke
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2012.1.00303.S, 2012.1.00631.S, 2013.1.00100.S, 2013.1.00157.S, 2013.1.00498.S, 2015.1.00773.S, 2015.1.00979.S, 2015.1.01600.S, 2016.1.00336.S, 2016.1.00340.S, 2016.1.00344.S, 2016.1.00484.L, 2016.1.00826.S, 2017.1.01424.S, 2018.1.00689.S, 2018.1.01458.S, 2021.1.00709.S, 2021.1.00854.S, 2021.1.01137.S, 2022.1.01302.S
BibCode: 2026A&A...706A.214V

Context. Polycyclic aromatic hydrocarbons (PAHs) are commonly detected in protoplanetary disks, but it is unclear what causes the wide range of intensities across the samples. Aims. For this work, the measured PAH intensities of a range of disks were compared with ALMA dust continuum images in order to test whether there is evidence that PAHs are frozen out on pebbles in dust traps and only sublimate under certain conditions. Methods. A sample was constructed from 26 T Tauri and Herbig disks located within 300 pc, with constraints on the 3.3 μm PAH intensity and with high-resolution ALMA continuum data. The midplane temperature was derived using a power law or via radiative transfer modeling. The warm dust mass was computed by integrating the flux within the 30 K radius and converted to a dust mass. Results. A strong correlation with a Pearson coefficient of 0.88±0.07 between the 3.3 μm PAH intensity and the warm dust mass was found. The correlation is driven by the combination of deep upper limits and strong detections corresponding to a range of warm dust masses. Possible correlations with other disk properties, for example a far-UV radiation field or total dust mass, are much weaker. Correlations with PAH features at 6.2, 8.6, and 11.3 μm are potentially weaker, but this could be explained by the smaller sample for which these data were available. Conclusions. The correlation is consistent with the hypothesis that PAHs are generally frozen out on pebbles in disks, and are only revealed in the gas phase if those pebbles have drifted toward warm dust traps inside the 30 K radius and vertically transported upward to the disk atmosphere with sufficiently high temperature to sublimate PAHs into the gas phase. This is similar to previous findings on complex organic molecules in protoplanetary disks, and provides further evidence that the chemical composition of the disk is governed by pebble transport.

Tracing Pebble Drift History in Two Protoplanetary Disks with CO Enhancement

First Author: Armitage, Tayt
Instruments: ALMA_Band_3, ALMA_Band_5, ALMA_Band_6
ProgramIDs: 2018.1.01055.L, 2021.1.00899.S
BibCode: 2026ApJ...998..308A

Pebble drift is an important mechanism for supplying the materials needed to build planets in the inner region of protoplanetary disks. Thus, constraining pebble drift's timescales and mass flux is essential to understanding planet formation history. Current pebble drift models suggest pebble fluxes can be constrained from the enhancement of gaseous volatile abundances when icy pebbles sublimate after drifting across key snowlines. In this work, we present Atacama Large Millimeter/submillimeter Array observations of spatially resolved ¹³C¹⁸O J = 2─1 line emission inside the midplane CO snowline of the HD 163296 and MWC 480 protoplanetary disks. We use radiative transfer and thermochemical models to constrain the spatial distribution of CO gas column density. We find that both disks display centrally peaked CO abundance enhancement of up to 10 times of the Interstellar Medium (ISM) abundance levels. For HD 163296 and MWC 480, the inferred enhancements require 250─350 and 480─660 M_⊕ of pebbles to have drifted across their CO snowlines, respectively. These ranges fall within cumulative pebble mass flux ranges to grow gas giants in the interior to the CO snowline. The centrally peaked CO enhancement is unexpected in current pebble drift models, which predict CO enhancement peaks at the CO snowline, or is uniform inside the snowline. We propose two hypotheses to explain the centrally peaked CO enhancement, including a large CO desorption distance and CO trapped in water ice. By testing both hypotheses with the 1D gas and dust evolution code chemcomp, we find that volatile trapping (about 30%) best reproduces the centrally peaked CO enhancement observed.

Testing the Physical Parameter Constraining Power of HCN and HNC with Neural Networks

First Author: Behrens, Erica
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_5, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2017.1.00161.L, 2018.1.00162.S
BibCode: 2026ApJ...998..274B

We quantify the utility of HCN and HNC to characterize gas conditions in the nearby starburst galaxy NGC 253. We use measurements from the Atacama Large Millimeter/Submillimeter Array (ALMA) Large Program ALCHEMI: the ALMA Comprehensive High-resolution Molecular Inventory. Using different subsets of the eight total HCN and HNC transitions measured by ALCHEMI, we test the number and combinations of transitions necessary for constraining the temperature, H₂ volume and column densities, cosmic-ray ionization rate, and beam-filling factor in three representative regions within NGC 253. We use these combinations of HCN and HNC transitions to constrain chemical and radiative transfer models, and infer the gas conditions using a Bayesian nested sampling algorithm combined with neural network models for increased efficiency. By comparing the shapes of the resulting posterior distributions, as well as the medians and uncertainties for each gas parameter, from each test case to what we obtain with the full set of eight transitions (the control), we quantify how well each test reproduces the control. We find that multiple transitions each of both molecules are required to obtain a median parameter value within a factor of 2 of the control with an uncertainty less than 2─3 times that of the control. We also find that transition combinations which feature a range of upper-state energies are most effective. We show that single transitions, such as HCN J = 1─0 or 3─2, are among the worst-performing combinations and result in parameter values up to an order of magnitude different than the control.

Unveiling the Chemical Complexity and C/O Ratio of the HD 163296 Protoplanetary Disk: Constraints from Multiline ALMA Observations of Organics, Nitriles, and Sulfur-bearing and Deuterated Molecules

First Author: Kashyap, Parashmoni
Instruments: ALMA_Band_4, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2018.1.00181.S, 2018.1.01055.L, 2021.1.00138.S
BibCode: 2026ApJS..282...47K

The physical and chemical conditions within a protoplanetary disk play a crucial role in determining its chemical composition, which is subsequently inherited by any forming planets. To probe these conditions, high-resolution molecular line observations, coupled with modeling, are essential. In this study, we investigate the chemistry of the nearby, massive, and relatively line-rich protoplanetary disk around HD 163296 using high-resolution observations from the Atacama Large Millimeter/submillimeter Array (ALMA) across Bands 3, 4, 6, and 7. We constrain the disk-averaged and radial distributions of column density and excitation temperature for the detected molecules using the new retrieval code DRive. The disk chemistry is modelled using the astrochemical code PEGASIS, with variations in the initial elemental C/O ratio. Our modelling, informed by molecular observations of HCO⁺, DCO⁺, HCN, DCN, CS, HC₃N, H₂CO, CH₃OH, HNCO, and NH₂CHO, allows us to place strong constraints on the C/O ratio, with a best-fit value of 1.1 that is broadly consistent with previous estimates. We present the highest-resolution DCO⁺ emission map of this disk to date, revealing triple-ringed chemical substructures that closely align with the dust continuum rings. Additionally, our results provide the first and most stringent upper limits on the column densities of NH₂CHO and HNCO in this protoplanetary disk, measured at <7 × 10¹¹ cm⁻² and <1 × 10¹¹ cm⁻², respectively. Our chemical models suggest that NH₂CHO and HNCO predominantly form on grain surfaces within the disk. However, physicochemical desorption mechanisms are inefficient at releasing these species into detectable gas-phase abundances, yet they remain promising targets for future ALMA observations.

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.

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