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We study the stellar mass function (SMF) and the co-evolution with dark matter halos via abundance matching in the largest redshift range to date $0.25$, we find increased abundances of massive (log$\, M_{\star}/M_{\odot}>10.5$) implying integrated star formation efficiencies (SFE) $\epsilon_{\star}\equiv M_{\star}\, f_{\rm b}^{-1} M_{\rm halo}^{-1} \gtrsim 0.5$. We find a flattening of the SMF at the high-mass end that is better described by a double power law at $z>5.5$. At $z \lesssim 5.5$ it transitions to a Schechter law which coincides with the emergence of the first massive quiescent galaxies in the Universe. We trace the cosmic stellar mass density (SMD) and infer the star formation rate density (SFRD), which at $z>7.5$ agrees remarkably with recent \JWST{} UV luminosity function-derived estimates. However, at $z \lesssim 3.5$, we find significant tension ($\sim 0.3$ dex) with the cosmic star formation (SF) history from instantaneous SF measures, the causes of which remain poorly understood. We infer the stellar-to-halo mass relation (SHMR) and the SFE from abundance matching out to $z=12$, finding a non-monotonic evolution. The SFE has the characteristic strong dependence with mass in the range of $0.02 - 0.2$, and mildly decreases at the low mass end out to $z\sim3.5$. At $z\sim3.5$ the SFE increases sharply from $\sim 0.1$ to approach high SFE of $0.8-1$ by $z\sim 10$ for log$(M_{\rm h}/M_{\odot})\approx11.5$, albeit with large uncertainties. Finally, we use the SHMR to track the SFE and stellar mass growth throughout the halo history and find that they do not grow at the same rate -- from the earliest times up until $z\sim3.5$ the halo growth rate outpaces galaxy assembly, but at $z>3.5$ halo growth stagnates and accumulated gas reservoirs keep the SF going and galaxies outpace halos.

The stellar mass-star formation rate (M$_\star$ - SFR) plane is essential for distinguishing galaxy populations, but how galaxies move within this plane over cosmic time remains unclear. This study aims to describe galaxy migrations in the M$_\star$ - SFR plane by reconstructing star formation histories (SFHs) for a sample of galaxies out to redshift $z < 4$. This provides insights into the physical processes driving star formation. We use data from the COSMOS field, selecting 299131 galaxies at $z < 4$ with COSMOS-Web NIRCam data (m$_\mathrm{F444W} < 27$) over 0.54 deg$^2$. Using the SED modeling code CIGALE with non-parametric SFHs, we derive physical properties and migration vectors for these galaxies. These vectors describe the direction and velocity of evolutionary paths across the M$_\star$ - SFR plane. To assess the accuracy of these vectors, we compare them to results from the Horizon-AGN simulation. Galaxies within the main sequence show low migration amplitudes and dispersed movement directions, indicating oscillation within the main sequence. Most progenitors were already on the main sequence a billion years earlier. Starburst galaxies assembled half their mass in the last 350 Myr and originated from the main sequence. Passive galaxies show uniformly declining SFHs and include massive galaxies already in the passive region at $z = 3.5-4$, with increasing density over time. Using reconstructed SFHs up to $z < 4$, we propose a coherent picture of how galaxies migrate over cosmic time in the M$_\star$ - SFR plane, highlighting the connection between major phases in the star-formation history.

The gas in the interstellar medium (ISM) of galaxies is supersonically turbulent. Measurements of turbulence typically rely on cold gas emission lines for low-z galaxies and warm ionized gas observations for z>0 galaxies. Studies of warm gas kinematics at z>0 conclude that the turbulence strongly evolves as a function of redshift, due to the increasing impact of gas accretion and mergers in the early Universe. However, recent findings suggest potential biases in turbulence measurements derived from ionized gas at high-z, impacting our understanding of turbulence origin, ISM physics and disk formation. We investigate the evolution of turbulence using velocity dispersion ($\sigma$) measurements from cold gas tracers (i.e., CO, [CI], [CII]) derived from a sample of 57 galaxy disks spanning the redshift range z=0-5. This sample consists of main-sequence and starburst galaxies with stellar masses $\gtrsim 10^{10} M_{\odot}$. The comparison with current H$\alpha$ kinematic observations and existing models demonstrates that the velocity dispersion inferred from cold gas tracers differ by a factor of $\approx 3$ from those obtained using emission lines tracing warm gas. We show that stellar feedback is the main driver of turbulence measured from cold gas tracers. This is fundamentally different from the conclusions of studies based on warm gas, which had to consider additional turbulence drivers to explain the high values of $\sigma$. We present a model predicting the redshift evolution of turbulence in galaxy disks, attributing the increase of $\sigma$ with redshift to the higher energy injected by supernovae due to the elevated star-formation rate in high-z galaxies. This supernova-driven model suggests that turbulence is lower in galaxies with lower stellar mass compared to those with higher stellar mass. Additionally, it forecasts the evolution of $\sigma$ in Milky-Way like progenitors., Comment: Accepted for publication in A&A. The abstract has been modified to comply with arXiv's character limit

Galaxy mergers play a critical role in galaxy evolution - altering the size, morphology, dynamics and composition of galaxies. So far, galaxy mergers have mostly been identified through visual inspection of their rest-frame optical and NIR emission. But, dust can obscure this emission, resulting in the misclassification of mergers as single galaxies, and the incorrect interpretation of their baryonic properties. Having serendipitously discovered a dust-obscured galaxy merger at z = 1.17, we aim to determine the baryonic properties of the two merging galaxies, including the star formation rate, and stellar, molecular gas, and dust masses. Using Band 3 and 6 observations from the Atacama Large Millimeter and submillimeter Array (ALMA), and ancillary data, we study the morphology of this previously misclassified merger. We deblend the emission, derive the gas masses from CO observations, and model the spectral energy distributions, to determine the properties of each galaxy. Using the rare combination of ALMA CO(2-1), CO(5-4) and dust-continuum (rest-frame 520um) observations, we provide insights into the gas and dust content and ISM properties of each merger component. We find that only one of the two galaxies is highly dust-obscured, whereas both are massive (> 10^10.5 Msun), highly star-forming (SFR = 60-900Msun/yr), have a moderate-to-low depletion time (tdepl < 0.7Gyr) and high gas fraction ( fgas >= 1). These properties can be interpreted as the positive impact of the merger. With this serendipitous discovery, we highlight the power of (sub)millimeter observations to identify and characterise the individual components of obscured galaxy mergers., Comment: 10 pages, 8 figures, accepted for publication to A&A

One of the surprising early findings with JWST has been the discovery of a strong "roll-over" or a softening of the absorption edge of Ly$\alpha$ in a large number of galaxies at ($z\gtrsim 6$), in addition to systematic offsets from photometric redshift estimates and fundamental galaxy scaling relations. This has been interpreted as damped Ly$\alpha$ absorption (DLA) wings from high column densities of neutral atomic hydrogen (HI), signifying major gas accretion events in the formation of these galaxies. To explore this new phenomenon systematically, we assemble the JWST/NIRSpec PRImordial gas Mass AssembLy (PRIMAL) legacy survey of 494 galaxies at $z=5.5-13.4$. We characterize this benchmark sample in full and spectroscopically derive the galaxy redshifts, metallicities, star-formation rates, and ultraviolet slopes. We define a new diagnostic, the Ly$\alpha$ damping parameter $D_{\rm Ly\alpha}$ to measure and quantify the Ly$\alpha$ emission strength, HI fraction in the IGM, or local HI column density for each source. The JWST-PRIMAL survey is based on the spectroscopic DAWN JWST Archive (DJA-Spec). All the software, reduced spectra, and spectroscopically derived quantities and catalogs are made publicly available in dedicated repositories. The fraction of strong galaxy DLAs are found to be in the range $65-95\%$ at $z>5.5$. The fraction of strong Ly$\alpha$ emitters (LAEs) is found to increase with decreasing redshift, in qualitative agreement with previous observational results, and are predominantly associated with low-metallicity and UV faint galaxies. By contrast, strong DLAs are observed in galaxies with a variety of intrinsic physical properties. Our results indicate that strong DLAs likely reflect a particular early assembly phase of reionization-era galaxies, at which point they are largely dominated by pristine HI gas accretion. [abridged], Comment: 20 pages, 18 figures, 3 tables. Submitted to A&A. Comments welcome! All data and catalogs are available through the DAWN JWST Archive (DJA): https://dawn-cph.github.io/dja/ and https://github.com/keheintz/jwst-primal

Early galaxy formation, initiated by the dark matter and gas assembly, evolves through frequent mergers and feedback processes into dynamically hot, chaotic structures. In contrast, dynamically cold, smooth rotating disks have been observed in massive evolved galaxies merely 1.4 billion years after the Big Bang, suggesting rapid morphological and dynamical evolution in the early Universe. Probing this evolution mechanism necessitates studies of young galaxies, yet efforts have been hindered by observational limitations in both sensitivity and spatial resolution. Here we report high-resolution observations of a strongly lensed and quintuply imaged, low-luminosity, young galaxy at $z=6.072$ (dubbed the Cosmic Grapes), 930 million years after the Big Bang. Magnified by gravitational lensing, the galaxy is resolved into at least 15 individual star-forming clumps with effective radii of $r_{\rm e}\simeq$ 10--60 parsec (pc), which dominate $\simeq$ 70\% of the galaxy's total flux. The cool gas emission unveils a smooth, underlying rotating disk characterized by a high rotational-to-random motion ratio and a gravitationally unstable state (Toomre $Q \simeq$ 0.2--0.3), with high surface gas densities comparable to local dusty starbursts with $\simeq10^{3-5}$ $M_{\odot}$/pc$^{2}$. These gas properties suggest that the numerous star-forming clumps are formed through disk instabilities with weak feedback effects. The clumpiness of the Cosmic Grapes significantly exceeds that of galaxies at later epochs and the predictions from current simulations for early galaxies. Our findings shed new light on internal galaxy substructures and their relation to the underlying dynamics and feedback mechanisms at play during their early formation phases, potentially explaining the high abundance of bright galaxies observed in the early Universe and the dark matter core-cusp problem., Comment: Submitted. 44 pages, 14 figures, 5 tables. Comments are welcome! See also the companion papers on arXiv. Valentino+2024: arXiv:2402.17845 Gim\'enez-Arteaga+2024: arXiv:2402.17875

We present JWST/NIRCam observations of a strongly-lensed, multiply-imaged galaxy at $z=6.072$, with magnification factors >~20 across the galaxy. We perform a spatially-resolved analysis of the physical properties at scales of ~200 pc, inferred from SED modelling of 5 NIRCam imaging bands on a pixel-by-pixel basis. We find young stars surrounded by extended older stellar populations. By comparing H$\alpha$+[NII] and [OIII]+H$\beta$ maps inferred from the image analysis with our additional NIRSpec IFU data, we find that the spatial distribution and strength of the line maps are in agreement with the IFU measurements. We explore different parametric SFH forms with Bagpipes on the spatially-integrated photometry, finding that a double power-law star formation history retrieves the closest value to the spatially-resolved stellar mass estimate, and other SFH forms suffer from the dominant outshining emission from the youngest stars, thus underestimating the stellar mass - up to ~0.5 dex-. On the other hand, the DPL cannot match the IFU measured emission lines. Additionally, the ionizing photon production efficiency may be overestimated in a spatially-integrated approach by ~0.15 dex, when compared to a spatially-resolved analysis. The agreement with the IFU measurements points towards the pixel-by-pixel approach as a way to mitigate the general degeneracy between the flux excess from emission lines and underlying continuum, especially when lacking photometric medium-band coverage and/or IFU observations. This study stresses the importance of studying galaxies as the complex systems that they are, resolving their stellar populations when possible, or using more flexible SFH parameterisations. This can aid our understanding of the early stages of galaxy evolution by addressing the challenge of inferring robust stellar masses and ionizing photon production efficiencies of high redshift galaxies., Comment: Submitted to A&A; 13 pages. See also the companion papers on arXiv today: Fujimoto+2024 and Valentino+2024

We present the results of a ~60-hr observational campaign with ALMA targeting a spectroscopically confirmed and lensed sub-$L^\star$ galaxy at z=6.07, identified during the ALMA Lensing Cluster Survey (ALCS). We sample the dust continuum emission from rest frame 90 to 370 $\mu$m at six different frequencies and set constraining upper limits on the molecular gas line emission and content via CO(7-6) and [CI](2-1) for two lensed images with $\mu\gtrsim20$. Complementing these sub-mm observations with deep optical and near-IR photometry and spectroscopy with JWST, we find this galaxy to form stars at a rate of SFR~7 Msun/yr, ~50-70% of which is obscured by dust. This is consistent with what is expected for a $M_\star$~7.5$\times10^{8}$ Msun object by extrapolating the $M_\star$-obscured SFR fraction relation at z<2.5 and with observations at 5

With the advent of JWST, we can probe the rest-frame optical emission of galaxies at $z>3$ with high sensitivity and spatial resolution, making it possible to accurately characterise red, optically-faint galaxies and thus move towards a more complete census of the galaxy population at high redshifts. To this end, we present a sample of 148 massive, dusty galaxies from the JWST/CEERS survey, colour-selected using solely JWST bands. With deep JWST/NIRCam data from 1.15$\mu$m to 4.44$\mu$m and ancillary HST/ACS and WFC3 data, we determine the physical properties of our sample using spectral energy distribution fitting with BAGPIPES. We demonstrate that our selection method efficiently identifies massive ($\mathrm{\langle \log M_\star/M_\odot \rangle \sim 10}$) and dusty ($\mathrm{\langle A_V\rangle \sim 2.7\ mag}$) sources, with a majority at $z>3$ and predominantly lying on the galaxy main-sequence. The main results of this work are the stellar mass functions (SMF) of red, optically-faint galaxies from redshifts between $3

We present a study of the mid-IR (MIR) emission of quiescent galaxies (QGs) beyond the local universe. Using deep $JWST$ imaging in the SMACS-0723 cluster field we identify a mass limited ($M_{*} >10^{9}$M$_{\odot}$) sample of intermediate redshift QGs ($0.2 5 \mu$m, can be attributed to different dust continuum levels and/or the presence of Polycyclic Aromatic Hydrocarbons (PAHs) features. The latter would indicate enhanced 11.3- and 12.7 $\mu$m PAHs strengths with respect to those at 6.2- and 7.7$ \mu$m, consistent with the observed spectra of local ellipticals and indicative of soft radiation fields. Finally, we augment the average UV-to-MIR spectrum of the population with cold dust and gas emission in the far-IR/mm and construct a panchromatic UV-to-radio SED that can serve as a template for the future exploration of the interstellar medium of $z>0$ QGs with ALMA and $JWST$., Comment: The panchromatic QG SED has been made publicly available at http://www.georgiosmagdis.com/software

The chemical enrichment of dust and metals are vital processes in constraining the star formation history of the universe. Previously, the dust masses of high-redshift star-forming galaxies have been determined through their far-infrared continuum, however, equivalent, and potentially simpler, approaches to determining the metal masses have yet to be explored at $z\gtrsim 2$. Here, we present a new method of inferring the metal mass in the interstellar medium (ISM) of galaxies out to $z\approx 8$, using the far-infrared [CII]$-158\mu$m emission line as a proxy. We calibrated the [CII]-to-$M_{\rm Z,ISM}$ conversion factor based on a benchmark observational sample at $z\approx 0$, in addition to gamma-ray burst sightlines at $z>2$ and cosmological hydrodynamical simulations of galaxies at $z\approx 0$ and $z\approx 6$. We found a universal scaling across redshifts of $\log (M_{\rm Z,ISM}/M_\odot) = \log (L_{\rm [CII]}/L_\odot) - 0.45,$ with a 0.4 dex scatter, which is constant over more than two orders of magnitude in metallicity. We applied this scaling to recent surveys for [CII] in galaxies at $z\gtrsim 2$ and determined the fraction of metals retained in the gas-phase ISM, $M_{\rm Z,ISM} / M_\star$, as a function of redshift showing that an increasing fraction of metals reside in the ISM of galaxies at higher redshifts. We place further constraints on the cosmic metal mass density in the ISM ($\Omega_{\rm Z,ISM}$) at $z\approx 5$ and $\approx 7$, yielding $\Omega_{\rm Z,ISM} = 6.6^{+13}_{-4.3}\times 10^{-7}\,M_\odot\, {\rm Mpc}^{-3}$ ($z\approx 5$) and $\Omega_{\rm Z,ISM} = 2.0^{+3.5}_{-1.3}\times 10^{-7}\,M_\odot\, {\rm Mpc}^{-3}$ ($z\approx 7$). These results are consistent with the expected metal yields from the integrated star formation history at the respective redshifts. This suggests that the majority of metals produced at $z\gtrsim 5$ are confined to the ISM of galaxies., Comment: Accepted in A&A, abstract abridged

Post-starburst galaxies are sources that had the last major episode of star formation about 1 Gyr before the epoch of the observations and are on their way to quiescence. It is important to study such galaxies at redshift z > 1, during their main quenching phase, and estimate their molecular gas content to constrain the processes responsible for the cessation of star formation. We present CO(3-2) ALMA observations of two massive (Mstar ~ 5 x 10^10 Msun) post-starburst galaxies at z > 1. We measure their molecular gas fraction to be f_H2 = M_H2/Mstar ~ 8% - 16%, consistent with z < 1 post-starburst galaxies from the literature. The star formation efficiency of our targets is ~ 10x lower than that of star-forming galaxies at similar redshift, and they are outliers of the f_H2 - specific star formation rate (sSFR) relation of star-forming galaxies, as they have larger f_H2 than expected given their sSFR. The gas fraction of post-starbursts from our sample and the literature correlates with the Dn4000 spectral index, a proxy of the stellar population age. This suggests that their gas content decreases after the last major burst of star formation. Finally, one of our targets is undergoing a major merger phase with two highly star-forming companions. This hints at a picture where a perturber event (e.g., major merger) quenches star formation without completely removing the molecular gas., Comment: Accepted for publication in MNRAS

The ALMA lensing cluster survey (ALCS) is a 96-hr large program dedicated to uncovering and characterizing intrinsically faint continuum sources and line emitters with the assistance of gravitational lensing. All 33 cluster fields were selected from HST/Spitzer treasury programs including CLASH, Hubble Frontier Fields, and RELICS, which also have Herschel and Chandra coverages. The total sky area surveyed reaches $\sim$133 arcmin$^2$ down to a depth of $\sim$60 $\mu$Jy beam$^{-1}$ (1$\sigma$) at 1.2 mm, yielding 141 secure blind detections of continuum sources and additional 39 sources aided by priors. We present scientific motivation, survey design, the status of spectroscopy follow-up observations, and number counts down to $\sim$7 $\mu$Jy. Synergies with JWST are also discussed., Comment: 6 pages, 4 figures, Proceedings of the 7th Chile-Cologne-Bonn-Symposium: Physics and Chemistry of Star Formation, V. Ossenkopf-Okada, R. Schaaf, I. Breloy (eds.)

We utilise the unprecedented depth and resolution of recent early-release science (ERS) JWST observations to define the near-infrared counterparts of sub-millimetre selected galaxies (SMGs). We identify 45 SCUBA-2 SMG positions within The Cosmic Evolution Early Release Science Survey (CEERS) JWST/NIRCam fields. Through an analysis of multi-wavelength $p$-values, NIRCam colours and predicted SCUBA-2 fluxes, we define 43 JWST/NIRCam counterparts to the SCUBA-2 SMGs, finding a 63 per cent agreement with those identified in prior $HST$ studies. Using EaZy-py we fit the available HST and JWST observations to quantify the photometric redshifts of the NIRCam-SMGs, establishing a broad range of redshift from $z$$\approx$0.2$-$5.4 with a median of $z$$\approx$2.29, in agreement with other studies of SMGs. We analyse their rest-frame optical and near-infrared morphological properties (e.g. effective radius (R$_{\rm e}$), S\'ersic index ($n$), CAS, Gini and M$_{20}$), finding, on average, late-type disc-like morphologies with large scatter into the intermediate and merger regions of the non-parametric parameter space. For the non-merging galaxies, we find a median rest-frame optical size and S\'ersic index (and $1\sigma$ scatter) of R$_{\rm e}$=3.10$\pm$1.67kpc and $n$=0.96$\pm$0.66. Whilst in the rest-frame near-infrared we establish more compact, higher S\'ersic index morphologies (R$_{\rm e}$=1.64$\pm$0.97, $n$=1.85$\pm$0.63). We further establish that both the rest-frame optical and near-infrared effective radii correlate negatively (at a 2$\sigma$ level) with redshift whilst the S\'ersic index remains constant with cosmic time. Our results are consistent with the picture of inside-out galaxy evolution, with more centrally concentrated older stellar populations, and more extended, younger star-forming regions whose stellar emission is heavily attenuated in the central regions., Comment: Submitted for publication in A&A. Comments welcome. 18 pages

Spatially-resolved studies of the kinematics of galaxies provide crucial insights into their assembly and evolution, enabling to infer the properties of the dark matter halos, derive the impact of feedback on the ISM, characterize the outflow motions. To date, most of the kinematic studies at z=0.5-3.5 were obtained using emission lines tracing the warm, ionized gas. However, whether these provide an exhaustive or only a partial view of the dynamics of galaxies and of the properties of the ISM is still debated. Complementary insights on the cold gas kinematics are therefore needed. We present ALPAKA, a project aimed at gathering high-resolution observations of CO and [CI] emission lines of star-forming galaxies at z=0.5-3.5 from the ALMA public archive. With 147 hours of total integration time, ALPAKA assembles ~0.25'' observations for 28 star-forming galaxies, the largest sample with spatially-resolved cold gas kinematics as traced by either CO or [CI] at z>0.5. By combining multi-wavelength ancillary data, we derive the stellar masses ($M_{\star}$) and star-formation rates (SFR) for our targets, finding values of $M_{\star}\gtrsim 10^{10}$ M$_{\odot}$ and SFR of 10-3000 M$_{\odot}$/yr. A large fraction of ALPAKA galaxies (19/28) lie in overdense regions (clusters, groups, and protoclusters). We exploit the ALMA data to infer their dynamical state and we find that 19/28 ALPAKA galaxies are rotating disks, 2 are interacting systems, while for the remaining 7 sources the classification is uncertain. The disks have velocity dispersion values that are typically larger in the innermost regions than in the outskirts, with a median value for the entire disk sample of 35$^{+11}_{-9}$ km/s. Despite the bias of our sample towards galaxies hosting very energetic mechanisms, the ALPAKA disks have high ratios of ordered-to-random motion ($V/\sigma$) with a median value of 9$^{+7}_{-2}$., Comment: 36 pages, 23 figures, 5 tables; accepted for publication in A&A. The data and the outputs of the kinematic analysis will be made available at https://alpaka-survey.github.io/index.html

We present a 1.1mm stacking analysis of moderately massive (log($M_{*}$/$M_{\odot}$) = 10.7 $\pm$ 0.2) quiescent galaxies (QGs) at $\langle z\rangle \sim1.5$, searching for cold dust continuum emission, an excellent tracer of dust and gas mass. Using both the recent GOODS-ALMA survey as well as the full suite of ALMA Band-6 ancillary data in the GOODS-S field, we report the tentative detection of dust continuum equivalent of dust mass log($M_{dust}$/$M_{\odot}$) = 7.47 $\pm$ 0.13 and gas mass log($M_{gas}$/$M_{\odot}$) = 9.42 $\pm$ 0.14. The emerging gas fraction is $f_{gas}$ = 5.3 $\pm$ 1.8%, consistent with the results of previous stacking analyses based on lower resolution sub(mm) observations. Our results support the scenario where high-z QGs have an order of magnitude larger $f_{gas}$ compared to their local counterparts and have experienced quenching with a non negligible gas reservoir in their interstellar medium - i.e. with gas retention. Subsequent analysis yields an anti-correlation between the $f_{gas}$ and the stellar mass of QGs, especially in the high mass end where galaxies reside in the most massive haloes. The $f_{gas}$ - $M_{*}$ anti-correlation promotes the selection bias as a possible solution to the tension between the stacking results pointing towards gas retention in high-z QGs of moderate $M_{*}$ and the studies of individual targets that favour a fully depleted ISM in massive (log($M_{*}$/$M_{\odot}$) high-z QGs., Comment: Accepted to A&A on the 16/03/2023

We present a joint analysis of the galaxy S04590 at $z=8.496$ based on NIRSpec, NIRCam, and NIRISS observations obtained through as part of Early Release Observations programme of the James Webb Space Telescope (JWST) and the far-infrared [CII]-$158\mu$m emission line detected by dedicated Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the physical properties of S04590 from modelling of the spectral energy distribution (SED) and through the redshifted optical nebular emission lines detected with JWST/NIRSpec. The best-fit SED model reveals a low-mass ($M_\star = 10^{7.2}-10^{8}\,M_{\odot}$) galaxy with a low oxygen abundance of $12+\log{\rm (O/H)} = 7.16^{+0.10}_{-0.12}$ derived from the strong nebular and auroral emission lines. Assuming that [CII] effectively traces the interstellar medium (ISM), we estimate the total gas mass of the galaxy to be $M_{\rm gas} = (8.0\pm 4.0)\times 10^{8}\,M_\odot$ based on the luminosity and spatial extent of [CII]. This yields an exceptionally high gas fraction, $f_{\rm gas} = M_{\rm gas}/(M_{\rm gas} + M_\star) \gtrsim 90\%$, though still consistent within the range expected for its low metallicity. We further derive the metal mass of the galaxy based on the gas mass and gas-phase metallicity, which we find to be consistent with the expected metal production from Type II supernovae. Finally, we make the first constraints on the dust-to-gas (DTG) and dust-to-metals (DTM) ratios of galaxies in the epoch of reionization at $z\gtrsim 6$, showing overall low mass ratios of logDGT $<-3.8$ and logDTM $<-0.5$, though consistent with local scaling relations and in particular the local metal-poor galaxy I Zwicky 18. Our analysis highlights the synergy between ALMA and JWST in characterizing the gas, metal, and stellar content of the first generation of galaxies., Comment: Accepted for publication in ApJL

How galaxies form, assemble, and cease their star-formation is a central question within the modern landscape of galaxy evolution studies. These processes are indelibly imprinted on the galaxy stellar mass function (SMF). We present constraints on the shape and evolution of the SMF, the quiescent galaxy fraction, and the cosmic stellar mass density across 90% of the history of the Universe from $z=7.5\rightarrow0.2$ via the COSMOS survey. Now with deeper and more homogeneous near-infrared coverage exploited by the COSMOS2020 catalog, we leverage the large 1.27 deg$^{2}$ effective area to improve sample statistics and understand cosmic variance particularly for rare, massive galaxies and push to higher redshifts with greater confidence and mass completeness than previous studies. We divide the total stellar mass function into star-forming and quiescent sub-samples through $NUVrJ$ color-color selection. Measurements are then fitted with Schechter functions to infer the intrinsic SMF, the evolution of its key parameters, and the cosmic stellar mass density out to $z=7.5$. We find a smooth, monotonic evolution in the galaxy SMF since $z=7.5$, in agreement with previous studies. The number density of star-forming systems seems to have undergone remarkably consistent growth spanning four decades in stellar mass from $z=7.5\rightarrow2$ whereupon high-mass systems become predominantly quiescent (i.e. downsizing). An excess of massive systems at $z\sim2.5-5.5$ with strikingly red colors, some newly identified, increase the observed number densities to the point where the SMF cannot be reconciled with a Schechter function. Systematics including cosmic variance and/or AGN contamination are unlikely to fully explain this excess, and so we speculate that there may be contributions from dust-obscured objects similar to those found in FIR surveys. (abridged), Comment: 39 pages, 24 figures, accepted for publication in A&A. Data files containing key measurements are available for download: https://doi.org/10.5281/zenodo.7808832

While emission-selected galaxy surveys are biased towards the most luminous part of the galaxy population, absorption selection is a potentially unbiased galaxy selection technique with respect to luminosity. However, the physical properties of absorption-selected galaxies are not well characterised. Here we study the excitation conditions in the interstellar medium (ISM) in damped Ly$\alpha$ (DLA) absorption-selected galaxies. We present a study of the CO spectral line energy distribution (SLED) in four high-metallicity absorption-selected galaxies with previously reported CO detections at intermediate ($z \sim 0.7$) and high ($z \sim 2$) redshifts. We find further evidence for a wide variety of ISM conditions in these galaxies. Two out of the four galaxies show CO SLEDs consistent with that of the Milky Way inner disk. Interestingly, one of these galaxies is at $z \sim 2$ and has a CO SLED below that of main-sequence galaxies at similar redshifts. The other two galaxies at $z>2$ show more excited ISM conditions, with one of them showing thermal excitation of the mid-$J$ (J$=3, 4$) levels, similar to that seen in two massive main-sequence galaxies at these redshifts. Overall, we find that absorption selection traces a diverse population of galaxies., Comment: 10 pages, 5 figures, 6 tables, resubmitted to MNRAS after moderate revision

Understanding how super-massive black holes form and grow in the early Universe has become a major challenge since the discovery of luminous quasars only 700 million years after the Big Bang. Simulations indicate an evolutionary sequence of dust-reddened quasars emerging from heavily dust-obscured starbursts that then transition to unobscured luminous quasars by expelling gas and dust. Although the last phase has been identified out to a redshift of 7.6, a transitioning quasar has not been found at similar redshifts owing to their faintness at optical and near-infrared wavelengths. Here we report observations of an ultraviolet compact object, GNz7q, associated with a dust-enshrouded starburst at a redshift of z=7.1899+/-0.0005. The host galaxy is more luminous in dust emission than any other known object at this epoch, forming 1,600 solar masses of stars per year within a central radius of 480 parsec. A red point source in the far-ultraviolet is identified in deep, high-resolution imaging and slitless spectroscopy. GNz7q is extremely faint in X-rays, which indicates the emergence of a uniquely ultraviolet compact star-forming region or a Compton-thick super-Eddington black-hole accretion disk at the dusty starburst core. In the latter case, the observed properties are consistent with predictions from cosmological simulations and suggest that GNz7q is an antecedent to unobscured luminous quasars at later epochs., Comment: 49 pages, 15 figures, 2 tables. Authors' version. Published in the 14 April issue of Nature

We present new CO(2-1) observations of a representative sample of 24 local (z$<$0.02) luminous infrared galaxies (LIRGs) obtained at high spatial resolution ($<$100 pc) from ALMA. We derive the effective radii of the CO(2-1) and the 1.3 mm continuum emissions using the curve-of-growth method. LIRGs show an extremely compact cold molecular gas distribution (median R$_{CO}$ $\sim$0.7 kpc), which is a factor 2 smaller than the ionized gas, and 3.5 times smaller than the stellar size. The molecular size of LIRGs is similar to that of early-type galaxies (R$_{CO}\sim$1 kpc) and about a factor of 6 more compact than local Spirals of similar stellar mass. Only the CO emission in low-z ULIRGs is more compact than these local LIRGs by a factor of 2. Compared to high-z (1$<$z$<$6) systems, the stellar sizes and masses of local LIRGs are similar to those of high-z MS star-forming galaxies (SFG) and about a factor of 2-3 lower than sub-mm galaxies (SMG). The molecular sizes of high-z MS SFGs and SMGs are larger than those derived for LIRGs by a factor of $\sim$3 and $\sim$8, respectively. These results indicate that while low-z LIRGs and high-z MS-SFGs have similar stellar masses and sizes, the regions of current star formation (traced by the ionized gas) and of potential star-formation (traced by the molecular gas) are substantially smaller in LIRGs, and constrained to the central kpc region. High-z galaxies represent a wider population but their star-forming regions are more extended, even covering the overall size of the host galaxy. High-z galaxies have larger fractions of gas than low-z LIRGs, and therefore the formation of stars could be induced by interactions and mergers in extended disks or filaments with large enough molecular gas surface density involving physical mechanisms similar to those identified in the central kpc of LIRGs., Comment: 36 pages, 20 figures, 8 tables. Accepted for publication in A&A

We present Keck Cosmic Web Imager (KCWI) observations of giant Lya halos surrounding 9 galaxy groups and clusters at 2

Compact star formation appears to be generally common in dusty star-forming galaxies (SFGs). However, its role in the framework set by the scaling relations in galaxy evolution remains to be understood. In this work we follow up on the galaxy sample from the GOODS-ALMA 2.0 survey, an ALMA blind survey at 1.1mm covering a continuous area of 72.42arcmin$^2$ using two array configurations. We derived physical properties, such as star formation rates, gas fractions, depletion timescales, and dust temperatures for the galaxy sample built from the survey. There exists a subset of galaxies that exhibit starburst-like short depletion timescales, but they are located within the scatter of the so-called main sequence of SFGs. These are dubbed starbursts in the main sequence and display the most compact star formation and they are characterized by the shortest depletion timescales, lowest gas fractions, and highest dust temperatures of the galaxy sample, compared to typical SFGs at the same stellar mass and redshift. They are also very massive, accounting for $\sim 60\%$ of the most massive galaxies in the sample ($\log (M_{\rm{*}}/M_{\odot}) > 11.0$). We find trends between the areas of the ongoing star formation regions and the derived physical properties for the sample, unveiling the role of compact star formation as a physical driver of these properties. Starbursts in the main sequence appear to be the extreme cases of these trends. We discuss possible scenarios of galaxy evolution to explain the results drawn from our galaxy sample. Our findings suggest that the star formation rate is sustained in SFGs by gas and star formation compression, keeping them within the main sequence even when their gas fractions are low and they are presumably on the way to quiescence., Comment: Accepted by A&A. 26 pages, 13 figures

The Brownian loop soup is a conformally invariant statistical ensemble of random loops in two dimensions characterized by an intensity $\lambda>0$, with central charge $c=2 \lambda$. Recent progress resulted in an analytic form for the four-point function of a class of scalar conformal primary "layering vertex operators" $\mathcal{O}_{\beta}$ with dimensions $(\Delta, \Delta)$, with $\Delta = \frac{\lambda}{10}(1-\cos\beta)$, that compute certain statistical properties of the model. The Virasoro conformal block expansion of the four-point function revealed the existence of a new set of operators with dimensions $(\Delta+ k/3, \Delta + k'/3)$, for all non-negative integers $k, k'$ satisfying $|k-k'| = 0$ mod 3. In this paper we introduce the edge counting field $\mathcal E(z)$ that counts the number of loop boundaries that pass close to the point $z$. We rigorously prove that the $n$-point functions of $\mathcal E$ are well defined and behave as expected for a conformal primary field with dimensions $(1/3, 1/3)$. We analytically compute the four-point function $\langle \mathcal{O}_{\beta}(z_1) \mathcal{O}_{-\beta}(z_2) \mathcal{E}(z_3) \mathcal{E}(z_4) \rangle$ and analyze its conformal block expansion. The operator product expansions of $\mathcal{E} \times \mathcal{E}$ and $\mathcal{E} \times \mathcal{O}_{\beta}$ produce higher-order edge operators with "charge" $\beta$ and dimensions $(\Delta + k/3, \Delta + k/3)$. Hence, we have explicitly identified all scalar primary operators among the new set mentioned above. We also re-compute the central charge by an independent method based on the operator product expansion and find agreement with previous methods., Comment: 40 pages, 2 figures, clarified the relation to the scaling limit of critical percolation, corrected definition (2.3) and equations depending on it, corrected proof of Lemma 2.2, added Lemma A.2

Giant star-forming regions (clumps) are widespread features of galaxies at $z \approx 1-4$. Theory predicts that they can play a crucial role in galaxy evolution if they survive to stellar feedback for > 50 Myr. Numerical simulations show that clumps' survival depends on the stellar feedback recipes that are adopted. Up to date, observational constraints on both clumps' outflows strength and gas removal timescale are still uncertain. In this context, we study a line-emitting galaxy at redshift $z \simeq 3.4$ lensed by the foreground galaxy cluster Abell 2895. Four compact clumps with sizes $\lesssim$ 280 pc and representative of the low-mass end of clumps' mass distribution (stellar masses $\lesssim 2\times10^8\ {\rm M}_\odot$) dominate the galaxy morphology. The clumps are likely forming stars in a starbursting mode and have a young stellar population ($\sim$ 10 Myr). The properties of the Lyman-$\alpha$ (Ly$\alpha$) emission and nebular far-ultraviolet absorption lines indicate the presence of ejected material with global outflowing velocities of $\sim$ 200-300 km/s. Assuming that the detected outflows are the consequence of star formation feedback, we infer an average mass loading factor ($\eta$) for the clumps of $\sim$ 1.8 - 2.4 consistent with results obtained from hydro-dynamical simulations of clumpy galaxies that assume relatively strong stellar feedback. Assuming no gas inflows (semi-closed box model), the estimates of $\eta$ suggest that the timescale over which the outflows expel the molecular gas reservoir ($\simeq 7\times 10^8\ \text{M}_\odot$) of the four detected low-mass clumps is $\lesssim$ 50 Myr., Comment: 19 pages, 11 figures + Appendix. Published in MNRAS

We present a pilot search of CO emission in three H$_2$-absorbing, long-duration gamma-ray burst (GRB) host galaxies at z~2-3. We used the Atacama Large Millimeter/sub-millimeter Array (ALMA) to target the CO(3-2) emission line and report non-detections for all three hosts. These are used to place limits on the host molecular gas masses, assuming a metallicity-dependent CO-to-H$_2$ conversion factor ($\alpha_{\rm CO}$). We find, $M_{\rm mol} < 3.5\times 10^{10}\,M_{\odot}$ (GRB\,080607), $M_{\rm mol} < 4.7\times 10^{11}\,M_{\odot}$ (GRB\,120815A), and $M_{\rm mol} < 8.9\times 10^{11}\,M_{\odot}$ (GRB\,181020A). The high limits on the molecular gas mass for the latter two cases are a consequence of their low stellar masses $M_\star$ ($M_\star \lesssim 10^{8}\,M_{\odot}$) and low gas-phase metallicities ($Z\sim 0.03\,Z_{\odot}$). The limit on the $M_{\rm mol}/M_\star$ ratio derived for GRB\,080607, however, is consistent with the average population of star-forming galaxies at similar redshifts and stellar masses. We discuss the broader implications for a metallicity-dependent CO-to-H$_2$ conversion factor, and demonstrate that the canonical Galactic $\alpha_{\rm CO}$, will severely underestimate the actual molecular gas mass for all galaxies at $z>1$ with $M_\star < 10^{10}\,M_\odot$. To better quantify this we develop a simple approach to estimate the relevant $\alpha_{\rm CO}$ factor based only on the redshift and stellar mass of individual galaxies. The elevated conversion factors will make these galaxies appear CO-"dark" and difficult to detect in emission, as is the case for the majority of GRB hosts. GRB spectroscopy thus offers a complementary approach to identify low-metallicity, star-forming galaxies with abundant molecular gas reservoirs at high redshifts that are otherwise missed by current ALMA surveys., Comment: 7 pages, 5 Figs, accepted for publication in MNRAS

We characterise the basic far-IR (FIR) properties and the gas mass fraction of massive ( ~ 11.0) quiescent galaxies (QGs) and explore how these evolve from z = 2.0 to the present day. We use robust, multi-wavelength (mid- to far-IR and sub-millimetre to radio) stacking ensembles of homogeneously selected and mass complete samples of log(M*/Msun) > 10.8 QGs. We find that the dust to stellar mass ratio (Md/M*) rises steeply as a function of redshift up to z~1.0 and then remains flat at least out to z = 2.0. Using Md as a proxy of gas mass (Mgas), we find a similar trend for the evolution of the gas mass fraction (fgas) with z > 1.0 QGs having fgas ~ 7.0% (for solar metallicity). This fgas is 3 - 10 times lower than that of normal star forming galaxies (SFGs) at their corresponding redshift but ~3 and ~10 times larger compared to that of z = 0.5 and local QGs. Furthermore, the inferred gas depletion time scales are comparable to that of local SFGs and systematically longer than that of main sequence galaxies at their corresponding redshifts. Our analysis also reveals that the average dust temperature (Td) of massive QGs remains roughly constant (< Td > = 21.0 \pm 2.0K) at least out to z ~ 2.0 and is substantially colder (~ 10K) compared to that of z > 0 SFGs. This motivated us to construct and release a redshift-invariant template IR SED, that we use to make predictions for ALMA observations and to explore systematic effects in the Mgas estimates of massive, high-z QGs. Finally, we discuss how a simple model that considers progenitor-bias can effectively reproduce the observed evolution of Md/M* and fgas. Our results indicate universal initial interstellar medium conditions for quenched galaxies and a large degree of uniformity in their internal processes across cosmic time., Comment: Accepted for publication in A&A

We report the discovery of an intrinsically faint, quintuply-imaged, dusty galaxy MACS0600-z6 at a redshift $z=$6.07 viewed through the cluster MACSJ0600.1-2008 ($z$=0.46). A $\simeq4\sigma$ dust detection is seen at 1.2mm as part of the ALMA Lensing Cluster Survey (ALCS), an on-going ALMA Large program, and the redshift is secured via [C II] 158 $\mu$m emission described in a companion paper. In addition, spectroscopic follow-up with GMOS/Gemini-North shows a break in the galaxy's spectrum, consistent with the Lyman break at that redshift. We use a detailed mass model of the cluster and infer a magnification $\mu\gtrsim$30 for the most magnified image of this galaxy, which provides an unprecedented opportunity to probe the physical properties of a sub-luminous galaxy at the end of cosmic reionisation. Based on the spectral energy distribution, we infer lensing-corrected stellar and dust masses of $\rm{2.9^{+11.5}_{-2.3}\times10^9}$ and $\rm{4.8^{+4.5}_{-3.4}\times10^6}$ $\rm{M_{\odot}}$ respectively, a star formation rate of $\rm{9.7^{+22.0}_{-6.6} M_{\odot} yr^{-1}}$, an intrinsic size of $\rm{0.54^{+0.26}_{-0.14}}$ kpc, and a luminosity-weighted age of 200$\pm$100 Myr. Strikingly, the dust production rate in this relatively young galaxy appears to be larger than that observed for equivalent, lower redshift sources. We discuss if this implies that early supernovae are more efficient dust producers and the consequences for using dust mass as a probe of earlier star formation., Comment: submitted to MNRAS, revised version after including referee's comments

We report on the stellar content, half-light radii and star formation rates of a sample of 10 known high-redshift ($z\gtrsim 2$) galaxies selected on strong neutral hydrogen (HI) absorption (log(N(HI)/cm$^{-2})>19$) toward background quasars. We use observations from the {\it Hubble Space Telescope} (HST) Wide Field Camera 3 in three broad-band filters to study the spectral energy distribution(SED) of the galaxies. Using careful quasar point spread function subtraction, we study their galactic environments, and perform the first systematic morphological characterisation of such absorption-selected galaxies at high redshifts. Our analysis reveals complex, irregular hosts with multiple star-forming clumps. At a spatial sampling of 0.067 arcsec per pixel (corresponding to 0.55 kpc at the median redshift of our sample), 40% of our sample requires multiple S\'ersic components for an accurate modelling of the observed light distributions. Placed on the mass-size relation and the `main sequence' of star-forming galaxies, we find that absorption-selected galaxies at high redshift extend known relations determined from deep luminosity-selected surveys to an order of magnitude lower stellar mass, with objects primarily composed of star-forming, late-type galaxies. We measure half-light radii in the range $r_{1/2} \sim$ 0.4 to 2.6 kpc based on the reddest band (F160W) to trace the oldest stellar populations, and stellar masses in the range $\log (\mathrm{M}_{\star}/\mathrm{M}_{\odot}) \sim$ 8 to 10 derived from fits to the broad-band SED. Spectroscopic and SED-based star formation rates are broadly consistent, and lie in the range log(SFR/M$_{\odot} $yr$^{-1}$) $\sim$0.0 to 1.7., Comment: 17 pages, Accepted for publication in MNRAS. This revision has minor text changes

We report the discovery of a Multi Unit Spectroscopic Explorer (MUSE) galaxy group at z=4.32 lensed by the massive galaxy cluster ACT-CL J0102-4915 (aka El Gordo) at z=0.87, associated with a 1.2 mm source which is at a 2.07+/-0.88 kpc projected distance from one of the group galaxies. Three images of the whole system appear in the image plane. The 1.2 mm source has been detected within the Atacama Large Millimetre/submillimetre Array (ALMA) Lensing Cluster Survey (ALCS). As this ALMA source is undetected at wavelengths lambda < 2 microns, its redshift cannot be independently determined, however, the three lensing components indicate that it belongs to the same galaxy group at z=4.32. The four members of the MUSE galaxy group have low to intermediate stellar masses (~ 10^7-10^{10} Msun) and star formation rates (SFRs) of 0.4-24 Msun/yr, resulting in high specific SFRs (sSFRs) for two of them, which suggest that these galaxies are growing fast (with stellar-mass doubling times of only ~ 2x10^7 years). This high incidence of starburst galaxies is likely a consequence of interactions within the galaxy group, which is compact and has high velocity dispersion. Based on the magnification-corrected sub-/millimetre continuum flux density and estimated stellar mass, we infer that the ALMA source is classified as an ordinary ultra-luminous infrared galaxy (with associated dust-obscured SFR~200-300 Msun/yr) and lies on the star-formation main sequence. This reported case of an ALMA/MUSE group association suggests that some presumably isolated ALMA sources are in fact signposts of richer star-forming environments at high redshifts., Comment: 13 pages including 7 figures and 1 table. Accepted for publication at the ApJ. Minor changes with respect to version 1. Figure 6 has been expanded to broaden comparison with the literature

We define a large new class of conformal primary operators in the ensemble of Brownian loops in two dimensions known as the ``Brownian loop soup,'' and compute their correlation functions analytically and in closed form. The loop soup is a conformally invariant statistical ensemble with central charge $c = 2 \lambda$, where $\lambda > 0$ is the intensity of the soup. Previous work identified exponentials of the layering operator $e^{i \beta N(z)}$ as primary operators. Each Brownian loop was assigned $\pm 1$ randomly, and $N(z)$ was defined to be the sum of these numbers over all loops that encircle the point $z$. These exponential operators then have conformal dimension ${\frac{\lambda}{10}}(1 - \cos \beta)$. Here we generalize this procedure by assigning a more general random value to each loop. The operator $e^{i \beta N(z)}$ remains primary with conformal dimension $\frac {\lambda}{10}(1 - \phi(\beta))$, where $\phi(\beta)$ is the characteristic function of the probability distribution used to assign random values to each loop. Using recent results we compute in closed form the exact two-point functions in the upper half-plane and four-point functions in the full plane of this very general class of operators. These correlation functions depend analytically on the parameters $\lambda, \beta_i, z_i$, and on the characteristic function $\phi(\beta)$. They satisfy the conformal Ward identities and are crossing symmetric. As in previous work, the conformal block expansion of the four-point function reveals the existence of additional and as-yet uncharacterized conformal primary operators., Comment: 23 pages, 3 figures

We have discovered a 300kpc-wide giant Lya nebula centered on the massive galaxy group RO-1001 at z=2.91 in the COSMOS field. Keck Cosmic Web Imager observations reveal three cold gas filaments converging into the center of the potential well of its ~4x10^13Msun dark matter halo, hosting 1200Msun/yr of star formation as probed by ALMA and NOEMA observations. The nebula morphological and kinematics properties and the prevalence of blueshifted components in the Lya spectra are consistent with a scenario of gas accretion. The upper limits on AGN activity and overall energetics favor gravity as the primary Lya powering source and infall as the main source of gas flows to the system. Although interpretational difficulties remain, with outflows and likely also photoionization with ensuing recombination still playing a role, this finding provides arguably an ideal environment to quantitatively test models of cold gas accretion and galaxy feeding inside an actively star-forming massive halo at high redshift., Comment: 20 pages, 12 figures, 3 tables. Accepted for publication in A&A

Optically-compact star-forming galaxies (SFGs) have been proposed as immediate progenitors of quiescent galaxies, although their origin and nature are debated. Were they formed in slow secular processes or in rapid merger-driven starbursts? Addressing this question would provide fundamental insight into how quenching occurs. We explore the location of the general population of galaxies with respect to fundamental star-forming and structural relations, identify compact SFGs based on their stellar core densities, and study three diagnostics of the burstiness of star formation: 1) Star formation efficiency, 2) interstellar medium (ISM), and 3) radio emission. The overall distribution of galaxies in the fundamental relations points towards a smooth transition towards quiescence while galaxies grow their stellar cores, although some galaxies suddenly increase their specific star-formation rate when they become compact. From their star formation efficiencies compact and extended SFGs appear similar. In relation to the ISM diagnostic, by studying the CO excitation, the density of the neutral gas, and the strength of the ultraviolet radiation field, compact SFGs resemble galaxies located in the upper envelope of the SFGs main sequence, although yet based on a small sample size. Regarding the radio emission diagnostic we find that galaxies become increasingly compact as the starburst ages, implying that at least some compact SFGs are old starbursts. We suggest that compact SFGs could be starburts winding down and eventually crossing the main sequence towards quiescence., Comment: Accepted by ApJ. 18 pages, 8 figures

We investigate the contribution of clumps and satellites to the galaxy mass assembly. We analyzed spatially-resolved Hubble Space Telescope observations (imaging and slitless spectroscopy) of 53 star-forming galaxies at z ~ 1 - 3. We created continuum and emission line maps and pinpointed residual "blobs" detected after subtracting the galaxy disk. Those were separated into compact (unresolved) and extended (resolved) components. Extended components have sizes ~ 2 kpc and comparable stellar mass and age as the galaxy disks, whereas the compact components are 1.5 dex less massive and 0.4 dex younger than the disks. Furthermore the extended blobs are typically found at larger distances from the galaxy barycenter than the compact ones. Prompted by these observations and by the comparison with simulations, we suggest that compact blobs are in-situ formed clumps, whereas the extended ones are accreting satellites. Clumps and satellites enclose respectively ~ 20% and ~< 80% of the galaxy stellar mass, ~ 30% and ~ 20% of its star formation rate. Considering the compact blobs, we statistically estimated that massive clumps (Mstar >~ 10^9 Msun) have lifetimes of ~ 650 Myr, and the less massive ones (10^8 < Mstar < 10^9 Msun) of ~ 145 Myr. This supports simulations predicting long-lived clumps (lifetime > 100 Myr). Finally, ~< 30% (13%) of our sample galaxies are undergoing single (multiple) merger(s), they have a projected separation ~< 10 kpc, and the typical mass ratio of our satellites is 1:5 (but ranges between 1:10 and 1:1), in agreement with literature results for close pair galaxies., Comment: 20 pages (plus appendix), 8 figures, 2 tables. Accepted for publication in MNRAS

We present Atacama Large Millimetre Array and Atacama Compact Array observations of the Sunyaev-Zel'dovich effect in the z = 2 galaxy cluster Cl J1449+0856, an X-ray-detected progenitor of typical massive clusters in the present day Universe. While in a cleaned but otherwise untouched 92 GHz map of this cluster, little to no negative signal is visible, careful subtraction of known sub-millimetre emitters in the uv plane reveals a decrement at 5$\sigma$ significance. The total signal is -190$\pm$36 $\mu$Jy, with a peak offset by 5"-9" ($\sim$50 kpc) from both the X-ray centroid and the still-forming brightest cluster galaxy. A comparison of the recovered uv-amplitude profile of the decrement with different pressure models allows us to derive total mass constraints consistent with the $\sim$6$\times$10$^{13}$ M$_{\odot}$ estimated from X-ray data. Moreover, we find no strong evidence for a deviation of the pressure profile with respect to local galaxy clusters, although a slight tension at small-to-intermediate spatial scales suggests a flattened central profile, opposite to what seen in a cool core and possibly an AGN-related effect. This analysis of the lowest mass single SZ detection so far illustrates the importance of interferometers when observing the SZ effect in high-redshift clusters, the cores of which cannot be considered quiescent, such that careful subtraction of galaxy emission is necessary., Comment: 11 pages, 6 figures (+appendices); accepted for publication in Astronomy & Astrophysics

ALMA 870$\mu$m continuum imaging has uncovered a population of blends of multiple dusty star-forming galaxies (DSFGs) in sources originally detected with the Herschel Space Observatory. However, their pairwise separations are much smaller that what is found by ALMA follow-up of other single-dish surveys or expected from theoretical simulations. Using ALMA and VLA, we have targeted three of these systems to confirm whether the multiple 870$\mu$m continuum sources lie at the same redshift, successfully detecting $^{12}$CO($J = 3$-2) and $^{12}$CO($J = 1$-0) lines and being able to confirm that in the three cases all the multiple DSFGs are likely physically associated within the same structure. Therefore, we report the discovery of two new gas-rich dusty protocluster cores (HELAISS02, $z = 2.171 \pm 0.004$; HXMM20, $z = 2.602 \pm 0.002$). The third target is located in the well known COSMOS overdensity at $z = 2.51$ (named CL J1001+0220 in the literature), for which we do not find any new secure CO(1-0) detection, although some of its members show only tentative detections and require further confirmation. From the gas, dust, and stellar properties of the two new protocluster cores, we find very large molecular gas fractions yet low stellar masses, pushing the sources above the main sequence, while not enhancing their star formation efficiency. We suggest that the sources might be newly formed galaxies migrating to the main sequence. The properties of the three systems compared to each other and to field galaxies may suggest a different evolutionary stage between systems., Comment: Accepted by ApJ. 24 pages, 9 figures

ALMA measurements for 93 $Herschel$-selected galaxies at $1.1 \leqslant z \leqslant 1.7$ in COSMOS reveal a sizable ($>29$\%) population with compact star formation (SF) sizes, lying on average $> \times 3.6$ below the optical stellar mass ($M_{\star}$)-size relation of disks. This sample widely spans the star-forming Main Sequence (MS), having $10^{8} \leqslant M_{\star} \leqslant 10^{11.5} \ M_{\odot}$ and $20 \leqslant SFR \leqslant 680 \ M_{\odot} \rm yr^{-1}$. The 32 size measurements and 61 upper limits are measured on ALMA images that combine observations of CO(5-4), CO(4-3), CO(2-1) and $\lambda_{\rm obs} \sim 1.1-1.3 \ \rm mm$ continuum, all tracing the star-forming molecular gas. These compact galaxies have instead normally extended $K_{band}$ sizes, suggesting strong specific $SFR$ gradients. Compact galaxies comprise the $50\pm18 \%$ of MS galaxies at $M_{\star} > 10^{11} M_{\odot}$. This is not expected in standard bi-modal scenarios where MS galaxies are mostly steadily-growing extended disks. We suggest that compact MS objects are early post-starburst galaxies in which the merger-driven boost of SF has subsided. They retain their compact SF size until either further gas accretion restores pre-merger galaxy-wide SF, or until becoming quenched. The fraction of merger-affected SF inside the MS seems thus larger than anticipated and might reach $\sim 50$\% at the highest $M_{\star}$. The presence of large galaxies above the MS demonstrates an overall poor correlation between galaxy SF size and specific $SFR$., Comment: 7 pages, 5 figures. Accepted for publication in ApJ Letters

Gravitational-wave astronomy has the potential to substantially advance our knowledge of the cosmos, from the most powerful astrophysical engines to the initial stages of our universe. Gravitational waves also carry information about the nature of black holes. Here we investigate the potential of gravitational-wave detectors to test a proposal by Bekenstein and Mukhanov that the area of black hole horizons is quantized in units of the Planck area. Our results indicate that this quantization could have a potentially observable effect on the classical gravitational wave signals received by detectors. In particular, we find distorted gravitational-wave "echoes" in the post-merger waveform describing the inspiral and merger of two black holes. These echoes have a specific frequency content that is characteristic of black hole horizon area quantization., Comment: 15 pages, 7 figures

We study a population of significantly sub-solar enrichment galaxies at z=1.99, to investigate how molecular gas, dust and star-formation relate in low-metallicity galaxies at the peak epoch of star-formation. We target our sample with several deep ALMA and VLA datasets, and find no individual detections of CO[4-3], CO[1-0] or dust, in stark contrast to the $>$60% detection rate expected for solar-enrichment galaxies with these MS Halpha SFRs. We find that both low and high density molecular gas (traced by CO[1-0] and CO[4-3] respectively) are affected by the low enrichment, showing sample average (stacked) luminosity deficits $>$0.5-0.7 dex below expectations. This is particularly pertinent for the use of high-J CO emission as a proxy of instantaneous star-formation rate. Our individual galaxy data and stacked constraints point to a strong inverse dependence $\propto Z^{\gamma}$ of gas-to-dust ratios (G/D) and CO-to-H$_{2}$ conversion factors (aco) on metallicity at z$\sim$2, with $\gamma_{\rm G/D}<$-2.2 and $\gamma_{\alpha_{\rm CO}}<$-0.8, respectively. We quantify the importance of comparing G/D and aco vs. metallicity trends from the literature on a common, suitably normalised metallicity scale. When accounting for systematic offsets between different metallicity scales, our z$\sim$2 constraints on these scaling relations are consistent with the corresponding relations for local galaxies. However, among those local relations, we favour those with a steep/double power-law dependence of G/D on metallicity. Finally, we discuss the implications of these findings for (a) gas mass measurements for sub-M$^{*}$ galaxies, and (b) efforts to identify the characteristic galaxy mass scale contributing most to the comoving molecular gas density at z=2., Comment: 15 pages, 5 figures, 3 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society

We present the first results of an ALMA survey of the lower fine structure line of atomic carbon [C I]$(^3P_1\,-\,^{3}P_0)$ in far infrared-selected galaxies on the main sequence at $z\sim1.2$ in the COSMOS field. We compare our sample with a comprehensive compilation of data available in the literature for local and high-redshift starbursting systems and quasars. We show that the [C I]($^3P_1$$\rightarrow$$^3P_0$) luminosity correlates on global scales with the infrared luminosity $L_{\rm IR}$ similarly to low-$J$ CO transitions. We report a systematic variation of $L'_{\rm [C\,I]^3P_1\,-\, ^3P_0}$/$L_{\rm IR}$ as a function of the galaxy type, with the ratio being larger for main-sequence galaxies than for starbursts and sub-millimeter galaxies at fixed $L_{\rm IR}$. The $L'_{\rm [C\,I]^3P_1\,-\, ^3P_0}$/$L'_{\rm CO(2-1)}$ and $M_{\rm{[C I]}}$/$M_{\rm dust}$ mass ratios are similar for main-sequence galaxies and for local and high-redshift starbursts within a 0.2 dex intrinsic scatter, suggesting that [C I] is a good tracer of molecular gas mass as CO and dust. We derive a fraction of $f_{\rm{[C\,I]}} = M_{\rm{[C\,I]}} / M_{\rm{C}}\sim3-13$% of the total carbon mass in the atomic neutral phase. Moreover, we estimate the neutral atomic carbon abundance, the fundamental ingredient to calibrate [C I] as a gas tracer, by comparing $L'_{\rm [C\,I]^3P_1\,-\, ^3P_0}$ and available gas masses from CO lines and dust emission. We find lower [C I] abundances in main-sequence galaxies than in starbursting systems and sub-millimeter galaxies, as a consequence of the canonical $\alpha_{\rm CO}$ and gas-to-dust conversion factors. This argues against the application to different galaxy populations of a universal standard [C I] abundance derived from highly biased samples., Comment: 14 pages + Appendix. Accepted for publication in ApJ. All the data tables in Appendix will be also released in electronic format