Contribution of HI-bearing ultra-diffuse galaxies to the cosmic number density of galaxies

We estimate the cosmic number density of the recently identified class of HI-bearing ultra-diffuse sources (HUDs) based on the completeness limits of the ALFALFA survey. These objects have HI masses approximately in the range 8.5 < logM/M < 9.5, average r-band surface brightnesses fainter than 24 mag arcsec, half-light radii greater than 1.5 kpc, and are separated from neighbours by at least 350 kpc. In this work we demonstrate that they contribute at most ∼6% of the population of HI-bearing dwarfs detected by ALFALFA (with similar HI masses), have a total cosmic number density of (1.5 ± 0.6) × 10 Mpc, and an HI mass density of (6.0 ± 0.8) × 10 M Mpc. We estimate that this is similar to the total cosmic number density of ultra-diffuse galaxies (UDGs) in groups and clusters, and conclude that the relation between the number of UDGs hosted in a halo and the halo mass must have a break below M ∼ 10 M in order to account for the abundance of HUDs in the field. The distribution of the velocity widths of HUDs rises steeply towards low values, indicating a preference for slow rotation rates compared to the global HI-rich dwarf population. These objects were already included in previous measurements of the HI mass function, but have been absent from measurements of the galaxy stellar mass function owing to their low surface brightness. However, we estimate that due to their low number density the inclusion of HUDs would constitute a correction of less than 1%. Comparison with the Santa Cruz semi-analytic model shows that it produces HI-rich central UDGs that have similar colours to HUDs, but that these UDGs are currently produced in a much greater number. While previous results from this sample have favoured formation scenarios where HUDs form in high spin-parameter halos, comparisons with recent results which invoke that formation mechanism reveal that this model produces an order of magnitude more field UDGs than we observe in the HUD population, and these have an occurrence rate (relative to other dwarfs) that is approximately double what we observe. In addition, the colours of HUDs are bluer than predicted, although we suspect this is due to a systematic problem in reproducing the star formation histories of low-mass galaxies rather than being specific to the ultra-diffuse nature of these sources.© ESO 2018.MGJ acknowledges support from the grant AYA2015-65973-C3-1-R (MINECO/FEDER, UE).Peer Reviewe

Mock light-cones and theory friendly catalogues for the CANDELS survey

We present mock catalogues created to support the interpretation of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). We extract haloes along past light-cones from the Bolshoi Planck dissipationless N-body simulations and populate these haloes with galaxies using two different independently developed semi-analytic models of galaxy formation and the empirical model universemachine. Our mock catalogues have geometries that encompass the footprints of observations associated with the five CANDELS fields. In order to allow field-to-field variance to be explored, we have created eight realizations of each field. In this paper, we present comparisons with observable global galaxy properties, including counts in observed frame bands, luminosity functions, colour-magnitude distributions and colour-colour distributions. We additionally present comparisons with physical galaxy parameters derived from SED fitting for the CANDELS observations, such as stellar masses and star formation rates. We find relatively good agreement between the model predictions and CANDELS observations for luminosity and stellar mass functions. We find poorer agreement for colours and star formation rate distributions. All of the mock light-cones as well as curated 'theory friendly' versions of the observational CANDELS catalogues are made available through a web-based data hub. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Galaxy Morphology from z∼6z\sim6 through the eyes of JWST

International audienceWe analyze the Near Infrared ($\sim0.8-1\mu$m) rest-frame morphologies of galaxies with $\log M_*/M_\odot>9$ in the redshift range $010.5$) at $z\sim5$, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies $\sim1$ Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at $z>3$, with massive quiescent galaxies ($\log M_*/M_\odot>10.5$) being predominantly bulge-dominated

Galaxy Morphology from z∼6z\sim6 through the eyes of JWST

International audienceWe analyze the Near Infrared ($\sim0.8-1\mu$m) rest-frame morphologies of galaxies with $\log M_*/M_\odot>9$ in the redshift range $010.5$) at $z\sim5$, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies $\sim1$ Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at $z>3$, with massive quiescent galaxies ($\log M_*/M_\odot>10.5$) being predominantly bulge-dominated

Galaxy Morphology from z∼6z\sim6 through the eyes of JWST

International audienceWe analyze the Near Infrared ($\sim0.8-1\mu$m) rest-frame morphologies of galaxies with $\log M_*/M_\odot>9$ in the redshift range $010.5$) at $z\sim5$, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies $\sim1$ Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at $z>3$, with massive quiescent galaxies ($\log M_*/M_\odot>10.5$) being predominantly bulge-dominated

Galaxy Morphology from z∼6z\sim6 through the eyes of JWST

International audienceWe analyze the Near Infrared ($\sim0.8-1\mu$m) rest-frame morphologies of galaxies with $\log M_*/M_\odot>9$ in the redshift range $010.5$) at $z\sim5$, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies $\sim1$ Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at $z>3$, with massive quiescent galaxies ($\log M_*/M_\odot>10.5$) being predominantly bulge-dominated

Galaxy Morphology from z∼6z\sim6 through the eyes of JWST

International audienceWe analyze the Near Infrared ($\sim0.8-1\mu$m) rest-frame morphologies of galaxies with $\log M_*/M_\odot>9$ in the redshift range $010.5$) at $z\sim5$, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies $\sim1$ Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at $z>3$, with massive quiescent galaxies ($\log M_*/M_\odot>10.5$) being predominantly bulge-dominated

The ALMA Spectroscopic Survey in the HUDF: The Molecular Gas Content of Galaxies and Tensions with IllustrisTNG and the Santa Cruz SAM

The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS) provides new constraints for galaxy formation models on the molecular gas properties of galaxies. We compare results from ASPECS to predictions from two cosmological galaxy formation models: The IllustrisTNG hydrodynamical simulations and the Santa Cruz semianalytic model (SC SAM). We explore several recipes to model the H2 content of galaxies, finding them to be consistent with one another, and take into account the sensitivity limits and survey area of ASPECS. For a canonical CO-to-H2 conversion factor of CO = 3.6 M o/(K km s-1 pc2) the results of our work include: (1) the H2 mass of z &gt; 1 galaxies predicted by the models as a function of their stellar mass is a factor of 2-3 lower than observed; (2) the models do not reproduce the number of H2-rich () galaxies observed by ASPECS; (3) the H2 cosmic density evolution predicted by IllustrisTNG (the SC SAM) is in tension (in tension but with less disagreement than IllustrisTNG) with the observed cosmic density, even after accounting for the ASPECS selection function and field-to-field variance effects. The tension between models and observations at z &gt; 1 can be alleviated by adopting a CO-to-H2 conversion factor in the range CO = 2.0-0.8 M o/(K km s-1 pc2). Additional work on constraining the CO-to-H2 conversion factor and CO excitation conditions of galaxies through observations and theory will be necessary to more robustly test the success of galaxy formation models

Two Massive, Compact, and Dust-obscured Candidate z ≃ 8 Galaxies Discovered by JWST

We present a search for extremely red, dust-obscured, z > 7 galaxies with JWST/NIRCam+MIRI imaging over the first 20 arcmin2 of publicly available Cycle 1 data from the COSMOS-Web, CEERS, and PRIMER surveys. Based on their red color in F277W−F444W (∼2.5 mag) and detection in MIRI/F770W (∼25 mag), we identify two galaxies, COS-z8M1 and CEERS-z7M1, that have best-fit photometric redshifts of z = 8.4 − 0.4 + 0.3 and 7.6 − 0.1 + 0.1 , respectively. We perform spectral energy distribution fitting with a variety of codes (including bagpipes, prospector, beagle, and cigale) and find a >95% probability that these indeed lie at z > 7. Both sources are compact (R eff ≲ 200 pc) and highly obscured (A V ∼ 1.5-2.5) and, at our best-fit redshift estimates, likely have strong [O iii]+Hβ emission contributing to their 4.4 μm photometry. We estimate stellar masses of ∼1010 M ⊙ for both sources; by virtue of detection in MIRI at 7.7 μm, these measurements are robust to the inclusion of bright emission lines, for example, from an active galactic nucleus. We identify a marginal (2.9σ) Atacama Large Millimeter/submillimeter Array detection at 2 mm within 0.″5 of COS-z8M1, which, if real, would suggest a remarkably high IR luminosity of ∼1012 L ⊙. These two galaxies, if confirmed at z ∼ 8, would be extreme in their stellar and dust masses and may be representative of a substantial population of highly dust-obscured galaxies at cosmic dawn. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]