arXiv subjects

Gregory Rudnick

Publications and source records attributed to Gregory Rudnick.

At least 19 recordsLinked to original sources

arXiv2026

Virgo Filaments VIII: Characterizing the Structural Parameters of Virgo Galaxies with Machine Learning to Probe Environmental Quenching

A persistent challenge in galaxy evolution involves disentangling the many correlated properties in order to isolate the effects of a galaxy's environment on its star formation history. To address this multidimensionality problem, we apply k-means clustering to 2831 galaxies in the extended regions around the Virgo cluster to define objective, reproducible subsets of structurally similar galaxies. Using measurements of size, light distribution, and stellar mass, k-means partitions these galaxies into three feature classes (FCs): dwarfs, spheroids, and large disks. In addition to being structurally different, these FCs show distinct offsets from the star-forming main sequence to $>3\sigma$ significance, with the spheroid population systematically shifted to lower star formation rates. Examining environmental dependence within each FC, we find that denser environments are associated with progressively stronger quenching. However, star formation for the dwarf and large disk galaxies is not strongly affected until the rich group and cluster environments. For the spheroid galaxies, star formation instead smoothly decreases as environment density increases. We verify that these trends are not driven by differences in Sersic index within each environment, suggesting that the effectiveness of environmental quenching depends on the galaxy's structural class. Our results speak to the utility of a simple machine learning model to create broad classes of structurally similar galaxies based on a small set of parameters, which has important implications for navigating this data rich era of astronomy.

astro-ph.GA↗

arXiv2026

The GOGREEN Survey: AI Powered Deconvolution Lifts The Veil on Outside-in Environmental Quenching at z > 1

A powerful probe of the physical processes that quench star formation in dense environments is determining where within galaxies star formation is suppressed. At high redshift, the spatial resolution of multi-band imaging limits such measurements. We use deep-learning-based deconvolution to recover spatially resolved optical and near-infrared photometry for galaxies in nine GOGREEN clusters at 1<z<1.4, using customized models trained on HST and JWST imaging. Using resolved rest-frame UVJ colors, we classify galaxies by the star-forming states of their inner and outer regions into predominantly star-forming, predominantly quiescent, inside-quenched, or outside-quenched. We find that 24% of galaxies classified as quiescent from their integrated colors retain significant star formation. The predominantly quiescent fraction increases with stellar mass and is higher in clusters than in the field while the cluster quenched fraction excess is, when limiting to predominantly quenched galaxies, approximately 20%. Contrary to previous GOGREEN studies using integrated colors, we find this excess to be independent of stellar mass, demonstrating that partially quenched galaxies can bias measurements based on integrated colors. Among galaxies retaining significant star formation, outside-quenched galaxies are substantially more common than inside-quenched galaxies and have a fraction excess of (22.8+/-5.8)% in clusters relative to the field at low masses. This provides evidence that clusters preferentially suppress star formation in the outskirts of low-mass galaxies. Our results demonstrate the importance of spatially resolved classifications for interpreting environmental quenching at z~1 and the potential of deep-learning-based deconvolution to recover such information from large ground-based imaging datasets.

astro-ph.GA↗

arXiv2025

Distinct origins of environmentally quenched galaxies in the core and outer virialised regions of massive clusters at $0.8<z<1.5$

High-redshift ($z\sim1$) galaxy clusters are the domain where environmental quenching mechanisms are expected to emerge as important factors in the evolution of the quiescent galaxy population. Uncovering these initially subtle effects requires exploring multiple dependencies of quenching across the cluster environment, and through time. We analyse the stellar-mass functions (SMFs) of 17 galaxy clusters within the GOGREEN and GCLASS surveys between $0.8 9.5$. The data are fit simultaneously with a Bayesian model that allows the Schechter function parameters of the quiescent and star-forming populations to vary smoothly with cluster-centric radius and redshift. The model also fits the radial galaxy number density profile of each population, allowing the global quenched fraction to be parameterised as a function of redshift and cluster velocity dispersion. We find the star-forming SMF to not depend on radius or redshift. For the quiescent population however, there is $\sim2\sigma$ evidence for a radial dependence. Outside the cluster core ($R>0.3\,R_{\rm200}$), the quenched fraction above $\log{(M/{\rm{M_\odot}})}=9.5$ is $\sim40{\rm\;per\,cent}$, and the quiescent SMF is similar in shape to the star-forming field. In contrast, the cluster core has an elevated quenched fraction ($\sim70{\rm\;per\,cent}$), and a quiescent SMF similar in shape to the quiescent field population. We explore contributions of 'early mass-quenching' and mass-independent 'environmental-quenching' models in each of these radial regimes. The core is well-described primarily by early mass-quenching, which we interpret as accelerated quenching of massive galaxies in protoclusters, possibly through merger-driven feedback mechanisms. The non-core is better described through mass-independent, environmental-quenching of the infalling field population.

astro-ph.GA↗

arXiv2025

Virgo Filaments V: Disrupting the Baryon Cycle in the NGC 5364 Galaxy Group

The Virgo Filament Survey (VFS) is a comprehensive study of galaxies that reside in the extended filamentary structures surrounding the Virgo Cluster, out to 12 virial radii. The primary goal is to characterize all of the dominant baryonic components within galaxies and to understand whether and how they are affected by the filament environment. A key constituent of VFS is a narrowband H$\alpha$ imaging survey of over 600 galaxies, VFS-H$\alpha$. The H$\alpha$ images reveal detailed, resolved maps of the ionized gas and massive star-formation. This imaging is particularly powerful as a probe of environmentally-induced quenching because different physical processes affect the spatial distribution of star formation in different ways. In this paper, we present the first results from the VFS-H$\alpha$ for the NGC~5364 group, a low-mass ($\log_{10}(M_{dyn}/M_\odot) < 13)$ system located at the western edge of the Virgo~III filament. We combine H$\alpha$ imaging with resolved H~I observations from MeerKAT for eight group members. These galaxies exhibit peculiar morphologies, including strong distortions in the stars and the gas, truncated H~I and H$\alpha$ disks, H~I tails, extraplanar H$\alpha$ emission, and off-center H$\alpha$ emission. These signatures are suggestive of environmental processing such as tidal interactions, ram pressure stripping, and starvation. We quantify the role of ram pressure stripping expected in this group, and find that it can explain the cases of H~I tails and truncated H-alpha for all but one of the disk-dominated galaxies. Our observations indicate that multiple physical mechanisms are disrupting the baryon cycle in these group galaxies.

astro-ph.GA↗

arXiv2025

Traversing the Star-Forming Main Sequence with Molecular Gas Stacks of z~1.6 Cluster Galaxies

The cluster environment has been shown to affect the molecular gas content of cluster members, yet a complete understanding of this often subtle effect has been hindered due to a lack of detections over the full parameter space of galaxy star formation rates and stellar masses. Here we stack CO(2-1) spectra of z~1.6 cluster galaxies to explore the average molecular gas fractions of galaxies both at lower mass (log(M/solar mass)~9.6) and further below the Star Forming Main Sequence (SFMS; DeltaMS~ -0.9) than other literature studies; this translates to a 3sigma gas mass limit of ~7x10^9 solar masses for stacked galaxies below the SFMS. We divide our sample of 54 z~1.6 cluster galaxies, derived from the Spitzer Adaptation of the Red-Sequence Cluster Survey, into 9 groupings, for which we recover detections in 8. The average gas content of the full cluster galaxy population is similar to coeval field galaxies matched in stellar mass and star formation rate. However, when further split by CO-undetected and CO-detected, we find that galaxies below the SFMS have statistically different gas fractions from the field scaling relations, spanning deficiencies to enhancements from 2sigma below to 3sigma above the expected field gas fractions, respectively. These differences between z=1.6 cluster and field galaxies below the SFMS are likely due to environmental processes, though further investigation of spatially-resolved properties and more robust field scaling relation calibration in this parameter space are required.

astro-ph.GA↗

arXiv2025

Insights into environmental quenching at $z\sim1$: an enhancement of faint, low-mass passive galaxies in clusters

Understanding the processes that transform star-forming galaxies into quiescent ones is key to unraveling the role of environment in galaxy evolution. We present measurements of the luminosity functions (LFs) and stellar mass functions (SMFs) of passive red-sequence galaxies in four galaxy clusters at $0.8 < z < 1.3$, selected using deep VLT observations complemented with data from the GCLASS and GOGREEN surveys. We find a significant enhancement in the abundance of faint/low-mass passive galaxies in both the LFs and SMFs of all four clusters compared to the field. This is further evidenced by a shallower low-mass slope in the composite passive cluster SMF, which yields a Schechter parameter $\alpha = -0.54^{+\,0.03}_{-0.03}$, compared to $\alpha = 0.12^{+\,0.01}_{-0.01}$ for the field. Our findings indicate that quenching processes that act in clusters are enhanced compared to the field, suggesting that environmental quenching mechanisms may already be active by $z\sim1$. To reproduce the observed passive cluster SMF, we estimate that $25\pm5\%$ of the star-forming field population that falls into the cluster must have been quenched. Our results largely support traditional quenching models but highlight the need for deeper studies of larger cluster samples to better understand the role of environmental quenching in the distant Universe.

astro-ph.GA↗

arXiv2025

Deep Ultraviolet, Emission-Line Imaging of the Makani Galactic Wind

The OVI 1032, 1038 A line is a key probe of cooling gas in the circumgalactic medium (CGM) of galaxies, but has been observed to date primarily in absorption along single sightlines. We present deep HST ACS-SBC observations of the compact, massive starburst Makani. Makani hosts a 100 kpc, [OII]-emitting galactic wind driven by two episodes of star formation over 400 Myr. We detect OVI and Ly$\alpha$ emission across the [OII] nebula with similar morphology and extent, out to r ~ 50 kpc. Using differential narrow-band imaging, we separate Ly$\alpha$ and OVI and show that the OVI emission is comparable in brightness to [OII], with $L_{OVI} = 4\times10^{42}$ erg/s. The similar hourglass morphology and size of [OII] and OVI implicate radiative cooling at $T = 10^{5.5}$ K in a hot-cold interface. This may occur as the $T > 10^7$ K CGM -- or the hot fluid driving the wind -- exchanges mass with the $T \approx 10^4$ K clouds entrained in (or formed by) the wind. The optical/UV line ratios may be consistent with shock ionization, though uncertain attenuation and Ly$\alpha$ radiative transfer complicate the interpretation. The detection of OVI in Makani lies at the bleeding edge of the UV imaging capabilities of HST, and provides a benchmark for future emission-line imaging of the CGM with a wide-area UV telescope.

astro-ph.GA↗

arXiv2025

Recommended Actions for the American Astronomical Society: CSWA's Perspective on Steps for a more Inclusive Astronomy -- II. Recommendations

This paper, the second in a series of two, provides a set of recommendations that the American Astronomical Society (AAS) can take to create a more diverse and inclusive professional society for astronomers, with a focus on women astronomers. As noted in Paper I, now is the time for the AAS to take decisive action to transform astronomy into a diverse and inclusive profession. By combining the results of our 2019 survey, which is described in Paper I, peer-reviewed academic literature, and findings from many of the white papers submitted to Astro2020, the CSWA has developed 26 specific actions the AAS can take to help end harassment and bullying in astronomy; advance career development for astronomers who are women, members of other underrepresented groups, and intersections of these populations; and improve the climate and culture of AAS meetings. Actions to reduce rates of harassment and bullying include improvements to the AAS's anti-harassment policies and procedures and the development of astronomy-specific anti-harassment training resources. Actions to advance career development include creating a compensation database, improving how jobs are posted in the AAS Job Register, and supporting/enhancing a distance mentorship program. Finally, we call on the AAS to continue improving the accessibility of AAS meetings and to continue to support meeting sessions whose focus is to discuss issues of equity, diversity, and inclusion.

physics.soc-ph↗

arXiv2025

Recommended Actions for the American Astronomical Society: CSWA's Perspective on Steps for a more Inclusive Astronomy -- I. Background and Methods

In a series of two papers, we provide a comprehensive agenda of actions the American Astronomical Society (AAS) can take to create a more diverse and inclusive professional system for astronomers, with a focus on women astronomers. This first paper of the series outlines the background and methods, while the recommendations are treated in the second companion paper (Paper II). We take the stance that since the 2020 Decadal Survey (Astro2020) was delivered in 2021, with its first-ever set of recommendations on the State of the Profession, now is the time for the AAS to take decisive action to transform astronomy into a diverse and inclusive profession. In the spring of 2019, the CSWA surveyed the astronomical community to assess the popularity and feasibility of actions that the AAS can take to reduce harassment and advance career development for women in astronomy. Here we present the quantitative results of that survey and a synopsis of the free response sections, which are publicly accessible. By combining the results of our survey, peer-reviewed academic literature, and findings from many of the white papers submitted to Astro2020, the CSWA has developed 26 specific actions that the AAS can take to help end harassment in astronomy, to advance career development for astronomers who are women and who are other members of historically marginalized groups, and intersections of these populations, and to improve the climate and culture of AAS and AAS-sponsored meetings. This paper presents the data we used to make these recommendations, and the recommendations themselves will be presented in Paper II.

physics.soc-ph↗

arXiv2024

Virgo Filaments IV: Using WISE to Measure the Modification of Star-Forming Disks in the Extended Regions Around the Virgo Cluster

Recent theoretical work and targeted observational studies suggest that filaments are sites of galaxy preprocessing. The aim of the WISESize project is to directly probe galaxies over the full range of environments to quantify and characterize extrinsic galaxy quenching in the local Universe. In this paper, we use GALFIT to measure the infrared 12$\mu$m ($R_{12}$) and 3.4$\mu$m ($R_{3.4}$) effective radii of 603 late-type galaxies in and surrounding the Virgo cluster. We find that Virgo cluster galaxies show smaller star-forming disks relative to their field counterparts at the $2.5\sigma$ level, while filament galaxies show smaller star-forming disks to almost $1.5\sigma$. Our data, therefore, show that cluster galaxies experience significant effects on their star-forming disks prior to their final quenching period. There is also tentative support for the hypothesis that galaxies are preprocessed in filamentary regions surrounding clusters. On the other hand, galaxies belonging to rich groups and poor groups do not differ significantly from those in the field. We additionally find hints of a positive correlation between stellar mass and size ratio for both rich group and filament galaxies, though the uncertainties on these data are consistent with no correlation. We compare our size measurements with the predictions from two variants of a state-of-the-art semi-analytic model (SAM), one which includes starvation and the other incorporating both starvation and ram-pressure stripping (RPS). Our data appear to disfavor the SAM, which includes RPS for the rich group, filament, and cluster samples, which contributes to improved constraints for general models of galaxy quenching.

astro-ph.GA↗

arXiv2024

$Spitzer$-selected $z > 1.3$ protocluster candidates in the LSST Deep Drilling Fields

We have identified 189 candidate $z > 1.3$ protoclusters and clusters in the LSST Deep Drilling Fields. This sample will enable the measurement of the metal enrichment and star formation history of clusters during their early assembly period through the direct measurement of the rate of supernovae identified through the LSST. The protocluster sample was selected from galaxy overdensities in a $Spitzer$/IRAC colour-selected sample using criteria that were optimised for protocluster purity using a realistic lightcone. Our tests reveal that $60-80\%$ of the identified candidates are likely to be genuine protoclusters or clusters, which is corroborated by a $\sim4\sigma$ stacked X-ray signal from these structures. We provide photometric redshift estimates for 47 candidates which exhibit strong peaks in the photo-$z$ distribution of their candidate members. However, the lack of a photo-$z$ peak does not mean a candidate is not genuine, since we find a stacked X-ray signal of similar significance from both the candidates that exhibit photo-$z$ peaks and those that do not. Tests on the lightcone reveal that our pursuit of a pure sample of protoclusters results in that sample being highly incomplete ($\sim4\%$) and heavily biased towards larger, richer, more massive, and more centrally concentrated protoclusters than the total protocluster population. Most ($\sim75\%$) of the selected protoclusters are likely to have a maximum collapsed halo mass of between $10^{13}-10^{14}$ M$_{\odot}$, with only $\sim25\%$ likely to be collapsed clusters above $10^{14}$ M$_{\odot}$. However, the aforementioned bias ensures our sample is $\sim50\%$ complete for structures that have already collapsed into clusters more massive than $10^{14}$ M$_{\odot}$.

astro-ph.GA↗

arXiv2023

Roman-Cosmic Noon: A Legacy Spectroscopic Survey of Massive Field and Protocluster Galaxies at $2<z<3$

Protoclusters are the densest regions in the distant universe ($z>2$) and are the progenitors of massive galaxy clusters ($M_{halo}>10^{14}{\rm M}_\odot$) in the local universe. They undoubtedly play a key role in early massive galaxy evolution and they may host the earliest sites of galaxy quenching or even induce extreme states of star formation. Studying protoclusters therefore not only gives us a window into distant galaxy formation but also provides an important link in our understanding of how dense structures grow over time and modify the galaxies within them. Current protocluster samples are completely unable to address these points because they are small and selected in a heterogeneous way. We propose the Roman-Cosmic Noon survey, whose centerpiece is an extremely deep (30ksec) and wide area (10 deg$^2$) prism slitless spectroscopy survey to identify the full range of galaxy structures at $2 10^{10.5} {\rm M}_\odot$ across the full range of star formation histories as well as many more lower mass star-forming galaxies. The survey will also contain field galaxies to much lower masses than in the High Latitude Wide Area Survey, but over an area dwarfing any current or planned deep spectroscopy probe at $z>2$. With the prism spectroscopy and some modest additional imaging this survey will measure precise stellar mass functions, quenched fractions, galaxy and protocluster morphologies, stellar ages, emission-line based SFRs, and metallicities. It will have extensive legacy value well beyond the key protocluster science goals.

astro-ph.GA↗

arXiv2023

The Local Cluster Survey II: Disk-Dominated Cluster Galaxies with Suppressed Star Formation

We investigate the role of dense environments in suppressing star formation by studying $\rm \log_{10}(M_\star/M_\odot) > 9.7$ star-forming galaxies in nine clusters from the Local Cluster Survey ($0.0137 < z < 0.0433$) and a large comparison field sample drawn from the Sloan Digital Sky Survey. We compare the star-formation rate (SFR) versus stellar mass relation as a function of environment and morphology. After carefully controlling for mass, we find that in all environments, the degree of SFR suppression increases with increasing bulge-to-total (B/T) ratio. In addition, the SFRs of cluster and infall galaxies at a fixed mass are more suppressed than their field counterparts at all values of B/T. These results suggest a quenching mechanism that is linked to bulge growth that operates in all environments and an additional mechanism that further reduces the SFRs of galaxies in dense environments. We limit the sample to $B/T < 0.3$ galaxies to control for the trends with morphology and find that the excess population of cluster galaxies with suppressed SFRs persists. We model the timescale associated with the decline of SFRs in dense environments and find that the observed SFRs of the cluster core galaxies are consistent with a range of models including: a mechanism that acts slowly and continuously over a long (2-5 Gyr) timescale, and a more rapid ($<1$ Gyr) quenching event that occurs after a delay period of 1-6 Gyr. Quenching may therefore start immediately after galaxies enter clusters.

astro-ph.GA↗

arXiv2023

The satellite population around luminous red galaxies in the 25 square degree DESI Legacy Imaging Surveys Early Data Release

Luminous Red Galaxies, or LRGs, are representative of the most massive galaxies and were originally selected in the Sloan Digital Sky Survey as good tracers of large scale structure. They are dominated by by uniformly old stellar populations, have low star formation rates, early type morphologies, and little cold gas. Despite having old stellar populations and little in situ star formation, studies have shown that they have grown their stellar mass since z=1, implying that they grow predominantly via the accretion of satellites. Tests of this picture have been limited because of the lack of deep imaging data sets that both covers a large enough area of the sky to contain substantial numbers of LRGs and that also is deep enough to detect faint satellites. We use the 25 square degree Early Data Release (EDR) of the DESI Legacy Imaging Surveys to characterize the satellite galaxy population of LRGs out to z=0.65. The DESI Legacy Imaging Surveys are comprised of grz imaging to 2-2.5 mag deeper than SDSS and with better image quality. We use a new statistical background technique to identify excess populations of putative satellite galaxies around 1823 LRGs at 0.2<z<0.65. In three redshift and luminosity bins we measure the numbers of satellite galaxies and their r- color distribution down to rest-frame $g$-band luminosity limits at least 3.6 times fainter than L*. In addition, we develop a forward modeling technique and apply it to constrain the mean number of satellites in each of our redshift and luminosity bins. Finally, we use these estimates to determine the amount of stellar mass growth in LRGs down to the local Universe.

astro-ph.GA↗

arXiv2022

GOGREEN: a critical assessment of environmental trends in cosmological hydrodynamical simulations at z ~ 1

Recent observations have shown that the environmental quenching of galaxies at z ~ 1 is qualitatively different to that in the local Universe. However, the physical origin of these differences has not yet been elucidated. In addition, while low-redshift comparisons between observed environmental trends and the predictions of cosmological hydrodynamical simulations are now routine, there have been relatively few comparisons at higher redshifts to date. Here we confront three state-of-the-art suites of simulations (BAHAMAS+MACSIS, EAGLE+Hydrangea, IllustrisTNG) with state-of-the-art observations of the field and cluster environments from the COSMOS/UltraVISTA and GOGREEN surveys, respectively, at z ~ 1 to assess the realism of the simulations and gain insight into the evolution of environmental quenching. We show that while the simulations generally reproduce the stellar content and the stellar mass functions of quiescent and star-forming galaxies in the field, all the simulations struggle to capture the observed quenching of satellites in the cluster environment, in that they are overly efficient at quenching low-mass satellites. Furthermore, two of the suites do not sufficiently quench the highest-mass galaxies in clusters, perhaps a result of insufficient feedback from AGN. The origin of the discrepancy at low stellar masses (Mstar <~ 1E10 Msun), which is present in all the simulations in spite of large differences in resolution, feedback implementations, and hydrodynamical solvers, is unclear. The next generation of simulations, which will push to significantly higher resolution and also include explicit modelling of the cold interstellar medium, may help to shed light on the low-mass tension.

astro-ph.GA↗

arXiv2022

The GOGREEN Survey: Constraining the Satellite Quenching Timescale in Massive Clusters at $\boldsymbol{z} \gtrsim 1$

We model satellite quenching at $z \sim 1$ by combining $14$ massive ($10^{13.8} < M_{\mathrm{halo}}/\mathrm{M}_{\odot} < 10^{15}$) clusters at $0.8 < z < 1.3$ from the GOGREEN and GCLASS surveys with accretion histories of $56$ redshift-matched analogs from the IllustrisTNG simulation. Our fiducial model, which is parameterized by the satellite quenching timescale ($τ_{\rm quench}$), accounts for quenching in our simulated satellite population both at the time of infall by using the observed coeval field quenched fraction and after infall by tuning $τ_{\rm quench}$ to reproduce the observed satellite quenched fraction versus stellar mass trend. This model successfully reproduces the observed satellite quenched fraction as a function of stellar mass (by construction), projected cluster-centric radius, and redshift and is consistent with the observed field and cluster stellar mass functions at $z \sim 1$. We find that the satellite quenching timescale is mass dependent, in conflict with some previous studies at low and intermediate redshift. Over the stellar mass range probed ($M_{\star}> 10^{10}~\mathrm{M}_{\odot}$), we find that the satellite quenching timescale decreases with increasing satellite stellar mass from $\sim1.6~{\rm Gyr}$ at $10^{10}~\mathrm{M}_{\odot}$ to $\sim 0.6 - 1~{\rm Gyr}$ at $10^{11}~\mathrm{M}_{\odot}$ and is roughly consistent with the total cold gas (H{\scriptsize I}+H$_{2}$) depletion timescales at intermediate $z$, suggesting that starvation may be the dominant driver of environmental quenching at $z < 2$. Finally, while environmental mechanisms are relatively efficient at quenching massive satellites, we find that the majority ($\sim65-80\%$) of ultra-massive satellites ($M_{\star} > 10^{11}~\mathrm{M}_{\odot}$) are quenched prior to infall.

astro-ph.GA↗

arXiv2021

HST/WFC3 grism observations of $z\sim1$ clusters: Evidence for rapid outside-in environmental quenching from spatially resolved H$α$ maps

We present and publicly release (https://www.gclasshst.com) the first spatially resolved H$α$ maps of star-forming cluster galaxies at $z\sim1$, made possible with the Wide Field Camera 3 (WFC3) G141 grism on the Hubble Space Telescope (HST). Using a similar but updated method to 3D-HST in the field environment, we stack the H$α$ maps in bins of stellar mass, measure the half-light radius of the H$α$ distribution and compare it to the stellar continuum. The ratio of the H$α$ to stellar continuum half-light radius, $R[\mathrm{H}α/\mathrm{C}]=\frac{R_{\mathrm{eff, H}α}}{R_{\mathrm{eff, Cont}}}$, is smaller in the clusters by $(6\pm9)\%$, but statistically consistent within $1σ$ uncertainties. A negligible difference in $R[\mathrm{H}α/\mathrm{C}]$ with environment is surprising, given the higher quenched fractions in the clusters relative to the field. We postulate that the combination of high quenched fractions and no change in $R[\mathrm{H}α/\mathrm{C}]$ with environment can be reconciled if environmental quenching proceeds rapidly. We investigate this hypothesis by performing similar analysis on the spectroscopically-confirmed recently quenched cluster galaxies. 87% have H$α$ detections, with star formation rates $8\pm1$ times lower than star-forming cluster galaxies of similar stellar mass. Importantly, these galaxies have a $R[\mathrm{H}α/\mathrm{C}]$ that is $(81\pm8)\%$ smaller than coeval star-forming field galaxies at fixed stellar mass. This suggests the environmental quenching process occurred outside-in. We conclude that disk truncation due to ram-pressure stripping is occurring in cluster galaxies at $z\sim1$, but more rapidly and/or efficiently than in $z\lesssim0.5$ clusters, such that the effects on $R[\mathrm{H}α/\mathrm{C}]$ become observable just after the cluster galaxy has recently quenched.

astro-ph.GA↗

arXiv2021

The GOGREEN survey: Transition Galaxies and The Evolution of Environmental Quenching

We measure the rate of environmentally-driven star formation quenching in galaxies at $z\sim 1$, using eleven massive ($M\approx 2\times10^{14}\,\mathrm{M}_\odot$) galaxy clusters spanning a redshift range $1.0 10.5$) we do not find any significant excess of transition galaxies in clusters, relative to a comparison field sample at the same redshift. It is likely that such galaxies were quenched prior to their accretion in the cluster, in group, filament or protocluster environments. For lower stellar mass galaxies ($9.5<\log{M/\mathrm{M}_\odot}<10.5$) there is a small but significant excess of transition galaxies in clusters, accounting for an additional $\sim 5-10$ per cent of the population compared with the field. We show that our data are consistent with a scenario in which 20--30 per cent of low-mass, star-forming galaxies in clusters are environmentally quenched every Gyr, and that this rate slowly declines from $z=1$ to $z=0$. While environmental quenching of these galaxies may include a long delay time during which star formation declines slowly, in most cases this must end with a rapid ($τ<1$ Gyr) decline in star formation rate.

astro-ph.GA↗