Martin A. Zwaan

Context . Spatially resolved galaxy kinematics have been most extensively studied at z ∼ 0 and z > 1. The emerging consensus is that disks are common out to z ∼ 3 − 6, albeit with larger disk velocity dispersions. In this picture, z ∼ 0.5 appears as a key transition in several fundamental aspects, such as the main driver of disk gas turbulence and baryonic-dark matter (DM) mass budget. While at z ∼ 0 multi-tracer spatially resolved characterisation is most readily accessible to study galaxy dynamics, studies with more than one tracer are still sparse for most galaxies outside the local Universe. Aims . We exploited a unique dataset covering spatially resolved cold molecular gas observations with ALMA and spatially resolved ionised gas line emission and stellar continuum with MUSE to study the resolved kinematics of six galaxies at 0.43 < z < 0.83. Obtained as part of the MUSE-ALMA Haloes program and selected by their association with neutral atomic hydrogen (H I ) absorption systems, the galaxies span stellar masses from log( M _⋆ /M _⊙ ) = 10.1 − 11.8. Methods . Using the new ALMA/CO observations and combining them with the existing MUSE ionised gas data and Hubble Space Telescope stellar morphologies, we determined the kinematic nature of the sources by applying morpho-kinematic criteria. For those identified as rotating disks, we employed the forward-modelling parametric kinematic fitting code D YSMAL P Y to jointly model the H β and CO(2-1) observations of the galaxies, and we compared the results to theoretical predictions for pressure support in galaxies. For the stellar kinematics, we used pPXF to fit rest-frame optical stellar absorption features. Results . We find that four of the six galaxies can be classified as disks, and two of these galaxies have previously identified galaxy group members. The four disk galaxies exhibit elevated gas velocity dispersions compared to z ∼ 0 disks, in agreement with the interpolation of observed trends between z ∼ 0 and z > 1. The results are consistent with marginally stable gaseous disks, where gravity-driving still plays a role in addition to stellar feedback, although we find tentative evidence of a differentiation between a dynamically hotter warm phase and the cold gas ( σ _0,Hβ ∼ 1.7× σ _0,CO ). We derived the average DM fraction ⟨ f _DM ⟩ = 0.42 ± 0.14, which is consistent with observations at comparable epochs and stellar masses and surface densities. This study highlights the use and completeness of analysing a sample of galaxies in a self-consistent manner and using multi-wavelength observations to explore the physics of disk settling in a relatively less explored redshift range.

The success of an astronomical facility is measured by its scientific impact. A principal metric for this impact is the ensemble of peer-reviewed publications based on the observational data obtained by the facility. We present a comprehensive study of the statistics of the 4190 refereed publications of the Atacama Large Millimeter/Submillimeter Array (ALMA) in the period from 2012 to 2024. The publications have received 169,985 citations and are based on 2670 ALMA projects totalling 19,265 hr of 12 m-array-equivalent observing time. Our study analyses publication statistics related to various aspects, e.g., science categories, geographical distribution, archival research, time to publication, publication fraction, and citations. We also look into the community and compare ALMA with other facilities. We find that ALMA is a high-impact observatory with ∼70% of observed projects published, ∼40% of publications making use of archival data in 2024, more than 9400 unique authors, and a publication evolution following that of HST and VLT. Currently, the impact factor for ALMA publications is larger than that of all other major astronomical facilities. ALMA also plays a pivotal role in very long baseline interferometry, substantially contributing to landmark achievements such as capturing the first image of a black hole shadow.

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.

We present further results from the MUSE-ALMA Haloes survey, which includes 79 galaxies associated with strong H I absorption at z ∼ 0.5. As part of this effort, our ALMA Cycle 10 Large Program contributed new observations of 39 systems. This expands on the initial set of 21 systems in the MUSE-ALMA Haloes survey, bringing the total to 60 galaxies. Among the newly observed systems, we detect CO line emission in nine galaxies, corresponding to a 23% detection rate in a sample not selected by metallicity. When combined with prior MUSE-ALMA Haloes data, our total CO detection count rises to 12 out of 60 galaxies (20%), which effectively doubles the number of detected CO-emitting H I –selected galaxies at z ∼ 0.5 and probes a factor of ∼1.2 dex deeper in M H ₂ than earlier absorber studies. These sources, which were selected based on known circumgalactic H I gas, span a wide range of stellar masses and metallicities, providing a unique view of gas-rich environments. By comparing the molecular gas properties, traced through CO(2−1) and CO(3−2) transitions with existing information of their physical properties, such as star formation rates (SFRs) and gas-phase metallicities from VLT/MUSE and HST spectroscopy, we investigate how these systems relate to the population of normal star-forming galaxies at similar redshift. Our deep, unbiased CO observations of H I -selected galaxies reveal a dual behaviour in star formation efficiency. Low- M H ₂ systems form stars efficiently and follow the scaling relations of main-sequence galaxies, while high- M H ₂ systems exhibit suppressed star formation and lower-than-expected stellar masses, likely reflecting ongoing gas accretion or environmental regulation. This diversity indicates that H I absorbers trace both evolved, actively star-forming galaxies and younger or dynamically influenced systems that are still building their gas reservoirs. By reaching molecular gas masses more than 1 dex below previous studies, our survey provides a key step towards completing the baryon census at z ∼ 0.5 and characterising the molecular phase of the broader H I -selected population.

The success of an astronomical facility is measured by its scientific impact. A principal metric for this impact is the ensemble of peer-reviewed publications based on the observational data obtained by the facility. We present a comprehensive study of the statistics of the 4,190 refereed publications of the Atacama Large Millimeter/Submillimeter Array (ALMA) in the period from 2012 to 2024. The publications have received 169,985 citations and are based on 2,670 ALMA projects totalling 19,265 hours of 12-m-array-equivalent observing time. Our study analyses publication statistics related to various aspects, e.g. science categories, geographical distribution, archival research, time to publication, publication fraction, and citations. We also look into the community and compare ALMA with other facilities. We find that ALMA is a high-impact observatory with an average of 41 citations per publication, ~70% of observed projects published, ~40% of publications making use of archival data in 2024, more than 9,400 unique authors, and a publication evolution following that of HST and VLT. Currently, the impact factor for ALMA publications is larger than that of all other major astronomical facilities. ALMA also plays a pivotal role in very long baseline interferometry (VLBI), substantially contributing to landmark achievements such as capturing the first image of a black hole shadow.

Cold molecular gas, largely traced by CO emission, is the primary fuel for star formation, making it essential for understanding galaxy evolution. ALMA has made significant progress in the study of the cosmic evolution of cold molecular gas. Here, we exploit the ALMACAL survey to address issues relating to small sample sizes and cosmic variance, utilising calibration data from ALMA to compile a statistically significant and essentially unbiased sample of CO-selected galaxies. By employing a novel statistical approach to emission-line classification using semi-analytical models, we place strong constraints on the CO luminosity function and the cosmic evolution of molecular gas mass density (ρH₂) back to z ∼ 6. The cosmic molecular gas mass density increases with redshift, peaking around z ∼ 1.5, then slowly declines towards higher redshifts by ∼1 dex. Our findings confirm the key role of molecular gas in fuelling star formation. The new ρH₂ estimates allow us to revisit the cosmic baryon cycle, showing that the ratio of molecular gas-to-stellar mass density is consistent with the so-called bathtub model of baryons, which implies a continuous replenishment of gas. The cosmic gas depletion timescale, estimated on a global scale, is shown to be fairly constant at all redshifts. We emphasise the importance of surveys using multiple small fields rather than a single contiguous area to mitigate the effects of cosmic variance.

We present measurements of the neutral atomic hydrogen (H i) mass function (HiMF) and cosmic H i density (Ω_{H I}) at 0 ≤ z ≤ 0.088 from the Looking at the Distant Universe with MeerKAT Array (LADUMA) survey. Using LADUMA Data Release 1 (DR1), we analyze the HiMF via a new “recovery matrix” method that we benchmark against a more traditional modified maximum likelihood (MML) method. Our analysis, which implements a forward modeling approach, corrects for survey incompleteness and uses extensive synthetic source injections to ensure robust estimates of the HiMF parameters and their associated uncertainties. This new method tracks the recovery of sources in mass bins different from those in which they were injected and incorporates a Poisson likelihood in the forward modeling process, allowing it to correctly handle uncertainties in bins with few or no detections. The application of our analysis to a high-purity subsample of the LADUMA DR1 spectral line catalog in turn mitigates any possible biases that could result from the inconsistent treatment of synthetic and real sources. For the surveyed redshift range, the recovered Schechter function normalization, low-mass slope, and “knee” mass are ϕ * = 3.5 6 − 1.92 + 0.97 × 1 0 − 3 Mpc⁻³ dex⁻¹, α = − 1.1 8 − 0.19 + 0.08 , and log ( M * / M ⊙ ) = 10.0 1 − 0.12 + 0.31 , respectively, which together imply a comoving cosmic H i density of Ω H I = 3.0 9 − 0.47 + 0.65 × 1 0 − 4 . Our results show consistency between recovery matrix and MML methods and with previous low-redshift studies, giving confidence that the cosmic volume probed by LADUMA, even at low redshifts, is not an outlier in terms of its H i content.

We identify a chain of galaxies along an almost straight line in the nearby Universe with a projected length of ~5 Mpc. The galaxies are distributed within projected distances of only 7–105 kpc from the axis of the identified filament. They have redshifts in a very small range of z = 0.0361−0.0370 so that their radial velocities are consistent with galaxy proper motions. The filament galaxies are mainly star forming and have stellar masses in a range of 10^9.1−10^10.7 M _⊙. We search for systems with similar geometrical properties in the full-sky mock galaxy catalog of the MillenniumTNG simulations and find that, although such straight filaments are unusual and rare, they are predicted by ΛCDM simulations (4% incidence). We study the cold H i gas in a 1.3 Mpc section of the filament through H i 21 cm emission line observations and detect 11 H i sources, many more than expected from the H i mass function in a similar volume. They have H i masses 10^8.5−10^9.5 M _⊙ and are mostly within ~120 kpc projected distance from the filament axis. None of these H i sources has a confirmed optical counterpart. Their darkness together with their large H i 21 cm line widths indicates that they contain gas that might not yet be virialized. These clouds must be marking the peaks of the dark matter and H i distributions over large scales within the filament. The presence of such gas clouds around the filament spines is predicted by simulations, but this is the first time that the existence of such clouds in a filament is observationally confirmed.

The ALMACAL survey is based on a database of reprocessed ALMA calibration scans suitable for scientific analysis, observed as part of regular PI observations. We present all the data accumulated from the start of ALMA operations until May 2022 for 1047 calibrator fields across the southern sky spanning ALMA Bands 3 to 10 ($ 84 - 950$ GHz), so-called ALMACAL$-22$. Encompassing over 1000 square arcmin and accumulating over 2000 hours of integration time, ALMACAL is not only one of the largest ALMA surveys to date, but it continues to grow with each new scientific observation. We outline the methods for processing and imaging a subset of the highest-quality data ('pruned sample'). Using deconvolution techniques within the visibility data (uv plane), we created data cubes as the final product for further scientific analysis. We describe the properties and shortcomings of ALMACAL and compare its area and sensitivity with other sub-millimetre surveys. Notably, ALMACAL overcomes limitations of previous sub-millimetre surveys, such as small sky coverage and the effects of cosmic variance. Moreover, we discuss the improvements introduced by the latest version of this dataset that will enhance our understanding of dusty star-forming galaxies, extragalactic absorption lines, active galactic nucleus physics, and ultimately the evolution of molecular gas.

We performed differential number counts down to 4.25 sigma using ALMA Band 3 calibrator images, which are known for their high dynamic range and susceptibility to various types of contamination. Estimating the fraction of contaminants is an intricate process due to correlated non-Gaussian noise, and it is often compounded by the presence of false positives generated during the cleaning phase. In addition, calibrator extensions further complicate the counting of background sources. In order to address these challenges, our strategy employs a machine learning-based approach utilizing the UMLAUT algorithm. UMLAUT assigns a value to each detection, and it considers how likely it is for there to be a genuine background source or a contaminant. With respect to this goal, we provide UMLAUT with eight observational input parameters, each automatically weighted using a gradient descent method. Our methodology significantly improves the precision of differential number counts, thus surpassing conventional techniques, including visual inspection. This study contributes to a better understanding of radio sources, particularly in the challenging sub-5 sigma regime, within the complex context of a high dynamic range of ALMA calibrator images.