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We determine the atomic hydrogen (H  i) to halo mass relation (HIHM) using Arecibo Legacy Fast ALFA survey H  i data at the location of optically selected groups from the Galaxy And Mass Assembly (GAMA) survey. We make direct H  i detections for 37 GAMA groups. Using H  i group spectral stacking of 345 groups, we study the group H  i content as a function of halo mass across a halo mass range of 1011–1014.7 M⊙. We also correct our results for Eddington bias. We find that the group H  i mass generally rises as a function of halo mass from 1.3% of the halo mass at |$10^{11.6} \, \text{M}_\odot$| to 0.4% at |$10^{13.7} \, \text{M}_\odot$| with some indication of flattening towards the high-mass end. Despite the differences in optical survey limits, group catalogues, and halo mass estimation methods, our results are consistent with previous group H  i -stacking studies. Our results are also consistent with mock observations from shark and IllustrisTNG. [ABSTRACT FROM AUTHOR]

We present a complete structural analysis of the ellipticals (E), diffuse bulges (dB), compact bulges (cB), and discs (D) within a redshift range 0 < z < 1, and stellar mass log10(M*/M⊙) ≥ 9.5 volume-limited sample drawn from the combined DEVILS and HST -COSMOS region. We use the profit code to profile over ∼35 000 galaxies for which visual classification into single or double component was pre-defined in Paper-I. Over this redshift range, we see a growth in the total stellar mass density (SMD) of a factor of 1.5. At all epochs we find that the dominant structure, contributing to the total SMD, is the disc, and holds a fairly constant share of |$\sim 60{{\ \rm per\ cent}}$| of the total SMD from z  = 0.8 to z  = 0.2, dropping to |$\sim 30{{\ \rm per\ cent}}$| at z  = 0.0 (representing |$\sim 33{{\ \rm per\ cent}}$| decline in the total disc SMD). Other classes (E, dB, and cB) show steady growth in their numbers and integrated stellar mass densities. By number, the most dramatic change across the full mass range is in the growth of diffuse bulges. In terms of total SMD, the biggest gain is an increase in massive elliptical systems, rising from 20 per cent at z  = 0.8 to equal that of discs at z  = 0.0 (30 per cent) representing an absolute mass growth of a factor of 2.5. Overall, we see a clear picture of the emergence and growth of all three classes of spheroids over the past 8 Gyr, and infer that in the later half of the Universe's timeline spheroid-forming processes and pathways (secular evolution, mass-accretion, and mergers) appear to dominate mass transformation over quiescent disc growth. [ABSTRACT FROM AUTHOR]

We present the first look at star formation histories of galaxy components using ProFuse , a new technique to model the 2D distribution of light across multiple wavelengths using simultaneous spectral and spatial fitting of purely imaging data. We present a number of methods to classify galaxies structurally/morphologically, showing the similarities and discrepancies between these schemes. We show the variation in componentwise mass functions that can occur simply due to the use of a different classification method, which is most dramatic in separating bulges and spheroids. Rather than identifying the best-performing scheme, we use the spread of classifications to quantify uncertainty in our results. We study the cosmic star formation history (CSFH), forensically derived using ProFuse with a sample of ∼7000 galaxies from the Galaxy And Mass Assembly survey. Remarkably, the forensic CSFH recovered via both our method (ProFuse) and traditional Spectral Energy Distribution (SED) fitting (ProSpect) are not only exactly consistent with each other over the past 8 Gyr, but also with the in situ CSFH measured using ProSpect. Furthermore, we separate the CSFH by contributions from spheroids, bulges, and discs. While the vast majority (70 per cent) of present-day star formation takes place in the disc population, we show that 50 per cent of the stars that formed at cosmic noon (8–12 Gyr ago) now reside in spheroids, and present-day bulges are composed of stars that were primarily formed in the very early Universe, with half their stars already formed ∼12 Gyr ago. [ABSTRACT FROM AUTHOR]

The presence of evolved stars in high-redshift galaxies can place valuable indirect constraints on the onset of star formation in the Universe. Thus, we use PEARLS GTO (Prime Extragalactic Areas for Reionization and Lensing Science Guaranteed Time Observations) and public NIRCam (Near Infrared Camera) photometric data to search for Balmer-break candidate galaxies at 7 < z < 12. We find that our Balmer-break candidates at z ∼ 10.5 tend to be older (115 Myr), have lower inferred [O  iii ] + Hβ equivalent widths (120 Å), have lower specific star formation rates (6 Gyr−1) and redder UV slopes (β = −1.8) than our control sample of galaxies. However, these trends all become less strong at z ∼ 8, where the F 444 W filter now probes the strong rest-frame optical emission lines, thus providing additional constraints on the current star formation activity of these galaxies. Indeed, the bursty nature of epoch of reionization galaxies can lead to a disconnect between their current spectral energy distribution (SED) profiles and their more extended star formation histories. We discuss how strong emission lines, the cumulative effect of weak emission lines, dusty continua, and active galactic nuclei can all contribute to the photometric excess seen in the rest-frame optical, thus mimicking the signature of a Balmer break. Additional medium-band imaging will thus be essential to more robustly identify Balmer-break galaxies. However, the Balmer break alone cannot serve as a definitive proxy for the stellar age of galaxies, being complexly dependent on the star formation history. Ultimately, deep Near Infrared Spectrograph (NIRSpec) continuum spectroscopy and Mid-Infrared Instrument (MIRI) imaging will provide the strongest indirect constraints on the formation era of the first galaxies in the Universe, thereby revealing when cosmic dawn breaks. [ABSTRACT FROM AUTHOR]

We present a pilot study to assess the potential of Hyper Suprime-Cam Public Data Release 2 (HSC-PDR2) images for the analysis of extended faint structures within groups of galaxies. We examine the intragroup light (IGL) of the group 400138 (M dyn = 1.3 ± 0.5 × 1013 M⊙, z ∼ 0.2) from the Galaxy And Mass Assembly (GAMA) survey using Hyper Suprime-Cam Subaru Strategic Program Public Data Release 2 (HSC-SSP PDR2) images in g, r , and i bands. We present the most extended IGL measurement to date, reaching down to |$\mu _{g}^{\rm {lim}}=30.76$|  mag arcsec−2 (3σ; 10 × 10 arcsec2) at a semimajor axis of 275 kpc. The IGL shows mean colour values of g − i  = 0.92, g − r  = 0.60, and r − i  = 0.32 (±0.01). The IGL stellar populations are younger (2–2.5 Gyr) and less metal rich ([Fe/H] ∼ −0.4) than those of the host group galaxies. We find a range of IGL fractions as a function of total group luminosity of |${\sim} 2\!-\!36 {{\ \rm per\ cent}}$| depending on the definition of IGL, with larger fractions the bluer the observation wavelength. The early-type to late-type galaxy ratio suggests that 400138 is a more evolved group, dominated by early-type galaxies, and the IGL fraction agrees with that of other similarly evolved groups. These results are consistent with tidal stripping of the outer parts of Milky Way-like galaxies as the main driver of the IGL build-up. This is supported by the detection of substructure in the IGL towards the galaxy member 1660615 suggesting a recent interaction (<1 Gyr ago) of that galaxy with the core of the group. [ABSTRACT FROM AUTHOR]

We derive single Sérsic fits and bulge-disc decompositions for 13 096 galaxies at redshifts z < 0.08 in the GAMA II equatorial survey regions in the Kilo-Degree Survey (KiDS) g, r , and i bands. The surface brightness fitting is performed using the Bayesian two-dimensional profile fitting code ProFit. We fit three models to each galaxy in each band independently with a fully automated Markov chain Monte Carlo analysis: a single Sérsic model, a Sérsic plus exponential and a point source plus exponential. After fitting the galaxies, we perform model selection and flag galaxies for which none of our models are appropriate (mainly mergers/Irregular galaxies). The fit quality is assessed by visual inspections, comparison to previous works, comparison of independent fits of galaxies in the overlap regions between KiDS tiles and bespoke simulations. The latter two are also used for a detailed investigation of systematic error sources. We find that our fit results are robust across various galaxy types and image qualities with minimal biases. Errors given by the MCMC underestimate the true errors typically by factors 2–3. Automated model selection criteria are accurate to |$\gt 90{{\ \rm per\ cent}}$| as calibrated by visual inspection of a subsample of galaxies. We also present g − r component colours and the corresponding colour–magnitude diagram, consistent with previous works despite our increased fit flexibility. Such reliable structural parameters for the components of a diverse sample of galaxies across multiple bands will be integral to various studies of galaxy properties and evolution. All results are integrated into the GAMA database. [ABSTRACT FROM AUTHOR]

We investigate changes in stellar population age and metallicity ([Z/H]) scaling relations for quiescent galaxies from intermediate redshift (0.60 ≤   |$z$| ≤ 0.76) using the LEGA-C Survey to low redshift (0.014 ≤   |$z$| ≤ 0.10) using the SAMI Galaxy Survey. Specifically, we study how the spatially integrated global age and metallicity of individual quiescent galaxies vary in the mass–size plane, using the stellar mass M * and a dynamical mass proxy derived from the virial theorem M D  ∝ σ2  R e. We find that, similarly to at low redshift, the metallicity of quiescent galaxies at 0.60 ≤   |$z$| ≤ 0.76 closely correlates with M / R e (a proxy for the gravitational potential or escape velocity), in that galaxies with deeper potential wells are more metal-rich. This supports the hypothesis that the relation arises due to the gravitational potential regulating the retention of metals by determining the escape velocity for metal-rich stellar and supernova ejecta to escape the system and avoid being recycled into later stellar generations. Conversely, we find no correlation between age and surface density (⁠|$M/R_\mathrm{e}^2$|⁠) at 0.60 ≤   |$z$| ≤ 0.76, despite this relation being strong at low redshift. We consider this change in the age– |$M/R_\mathrm{e}^2$| relation in the context of the redshift evolution of the star-forming and quiescent mass–size relations, and find our results are consistent with galaxies forming more compactly at higher redshifts and remaining compact throughout their evolution. Furthermore, galaxies appear to quench at a characteristic surface density that decreases with decreasing redshift. The |$z$| ∼  0 age– |$M/R_\mathrm{e}^2$| relation is therefore a result of building up the quiescent and star-forming populations with galaxies that formed at a range of redshifts and therefore a range of surface densities. [ABSTRACT FROM AUTHOR]

We measure how the atomic gas (H i) fraction f H I = M H I M * of groups and pairs taken as single units vary with average stellar mass (〈 M *〉) and average star formation rate (〈SFR〉), compared to isolated galaxies. The H i 21 cm emission observation are from (i) archival ALFALFA survey data covering three fields from the GAMA survey (provides environmental and galaxy properties), and (ii) DINGO pilot survey data of one of those fields. The mean f H i for different units (groups/pairs/isolated galaxies) are measured in regions of the log(〈 M *〉)â€"log(〈SFR〉) plane, relative to the z ∼ 0 star-forming main sequence (SFMS) of individual galaxies, by stacking f H i spectra of individual units. For ALFALFA, f H i spectra of units are measured by extracting H i spectra over the full groups/pair areas and dividing by the total stellar mass of member galaxies. For DINGO, f H i spectra of units are measured by co-adding H i spectra of individual member galaxies, followed by division by their total stellar mass. For all units, the mean f H i decreases as we move to higher 〈 M *〉 along the SFMS and as we move from above the SFMS to below it at any 〈 M *〉. From the DINGO-based study, mean f H i in groups appears to be lower compared to isolated galaxies for all 〈 M *〉 along the SFMS. From the ALFALFA-based study, we find substantially higher mean f H i in groups compared to isolated galaxies (values for pairs being intermediate) for 〈 M *〉 ≲ 109.5 M ⊙, indicating the presence of substantial amounts of H i not associated with cataloged member galaxies in low mass groups. [ABSTRACT FROM AUTHOR]