arXiv subjects

Gabriella De Lucia

Publications and source records attributed to Gabriella De Lucia.

At least 55 records · Page 3Linked to original sources

arXiv2024

What are the Pillars of Reionization? Revising the AGN Luminosity Function at z~5

In the past, high-z AGNs were given a minor role as possible drivers of reionization, despite initial evidences in favor of their large space densities at low luminosities by Chandra and HST. Recent observations from JWST are finding relatively large numbers of faint AGNs at z>4, convincingly confirming these early results. We present a sample of z~5 AGNs (both from wide, shallow ground-based surveys and from deep, pencil-beam observations from JWST), allowing to estimate their space densities with unprecedented accuracy. The bright end (M1450<-26) of the z~5 AGN luminosity function is well constrained, with a rather steep slope. The faint end (M1450>-22) indicates a high space density, the scatter is significant and the knee (M1450~-24) is mostly undetermined. Comparisons with state-of-the-art models find reasonable agreement with the observed AGN luminosity function at z=5, while the predicted space density evolution at higher redshifts appears to be too fast with respect to observational constraints. Given the large variance at the faint end, we consider different options in fitting the luminosity functions and deriving the ionizing emissivity. Even in the most conservative scenario, the photo-ionization rate produced by z~5 AGNs is consistent with the UV background measurements. A slow evolution of the space density of faint AGNs is observed, indicating that active SMBHs are probably producing large amounts of ionizing photons at z>6, well into the epoch of reionization. This is an important indication that high-z AGNs could be the major contributors to the reionization of the Universe.

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arXiv2024

Variation of the stellar initial mass function in semi-analytical models III: testing the cosmic ray regulated integrated galaxy-wide initial mass function

In our previous work, we derive the CR-IGIMF: a new scenario for a variable stellar initial mass function (IMF), which combines numerical results on the role played by cosmic rays in setting the thermal state of star forming gas, with the analytical approach of the integrated galaxy-wide IMF. In this work, we study the implications of this scenario for the properties of local Early-Type galaxies (ETG), as inferred from dynamical, photometric and spectroscopic studies. We implement a library of CR-IGIMF shapes in the framework of the Galaxy Evolution and Assembly (GAEA) model. Our realization includes a derivation of synthetic spectral energy distribution for each model galaxy, allowing a direct derivation of the mass fraction in the mean IMF of low-mass stars (i.e. the dwarf-to-giant ratio - $\rm f_{dg}$) and a comparison with IMF sensitive spectral features. The predictions of the GAEA model implementing the CR-IGIMF confirm our previous findings: it correctly reproduces both the observed excess of z$\sim$0 dynamical mass (mass-to-light ratios) with respect to spectroscopic (photometric) estimates assuming a universal, MW-like, IMF, and the observed increase of [$α$/Fe] ratios with stellar mass in spheroidal galaxies. Moreover, this realization reproduces the increasing trends of $\rm f_{dg}$, and IMF-sensitive line-strengths with velocity dispersion, although the predicted relations are significantly shallower than the observed ones. Our results show that the CR-IGIMF is a promising scenario that reproduces at the same time dynamical, photometric and spectroscopic indications of a varying IMF in local ETGs. The shallow relations found for spectral indices suggest that either a stronger variability as a function of galaxy properties or additional dependences (e.g. as a function of star forming gas metallicity) might be required to match the strength of the observed trends.

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arXiv2024

Tracing the Quenching Journey across Cosmic Time

We present the latest version of the GAEA model of galaxy formation. Our new model combines (i) an updated treatment of AGN feedback including an improved modelling of cold gas accretion on super-massive BHs and an explicit implementation of quasar winds; and (ii) an improved modelling of cold and hot gas stripping from satellite galaxies. We show that our latest model predicts specific SFR distributions that are in remarkable agreement with observational measurements in the local Universe. Our updated model predicts quenched fractions that are in very nice agreement with data up to z~3-4, and a turn-over of the number densities of quenched galaxies at low stellar masses that is in qualitative agreement with current observational estimates. We show that the main reasons for the improved behaviour with respect to previous renditions of our model are the updated treatment for satellites at low galaxy masses (<10^10 Msun) and the inclusion of quasar winds at intermediate to large stellar masses (>10^10 Msun). However, we show that the better treatment of the star formation threshold, due to our explicit partitioning of the cold gas in its atomic and molecular components, also plays an important role in suppressing excessive residual star formation in massive galaxies. While our analysis is based on a selection of quiescent galaxies that takes advantage of the information about their SFR, we demonstrate that the impact of a different (colour-colour) selection is not significant, at least for galaxies above the completeness limits of current surveys. Our new model predicts number densities of massive quiescent galaxies at z>3 that are the largest among recently published models. Yet, our model predictions appear still to be below post-JWST observational measurements. We show that the expected cosmic variance is large, and can easily accommodate some of the most recent measurements.

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arXiv2024

On the origin of globular clusters in a hierarchical Universe

We present an end-to-end description of the formation process of globular clusters (GCs) which combines a treatment for their formation and dynamical evolution within galaxy haloes with a state-of-the-art semi-analytic simulation of galaxy formation. Our approach allows us to obtain exquisite statistics to study the effect of the environment and assembly history of galaxies, while still allowing a very efficient exploration of the parameter space of star cluster physics. Our reference model, including both efficient cluster disruption during galaxy mergers and a model for the dynamical friction of GCs within the galactic potential, accurately reproduces the observed correlation between the total mass in GCs and the parent halo mass. A deviation from linearity is predicted at low halo masses, which is driven by a strong dependence on morphological type: bulge-dominated galaxies tend to host larger masses of GCs than their later-type counterparts of similar stellar mass. While the significance of the difference might be affected by resolution at the lowest halo masses considered, this is a robust prediction of our model and represents a natural consequence of the assumption that cluster migration from the disk to the halo is triggered by galaxy mergers. Our model requires an environmental dependence of GC radii to reproduce the observed mass distribution of GCs in our Galaxy at the low-mass end. At GC masses $>10^6\,{\rm M}_\odot$, our model predicts fewer GCs than observed due to an overly aggressive treatment of dynamical friction. The metallicity distribution measured for Galactic GCs is well reproduced by our model, even though it predicts systematically younger GCs than observed. We argue that this adds further evidence for an anomalously early formation of the stars in our Galaxy.

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arXiv2024

The first quenched galaxies, when and how?

Many quiescent galaxies discovered in the early Universe by \textit{JWST} raise fundamental questions on when and how these galaxies became and stayed quenched. Making use of the latest version of the semi-analytic model GAEA that provides good agreement with the observed quenched fractions up to $z\sim 3$, we make predictions for the expected fractions of quiescent galaxies up to $z\sim 7$ and analyze the main quenching mechanism. We find that in a simulated box of $685~{\rm Mpc}$ on a side, the first quenched massive ($M_{\star} \sim 10^{11} {\rm M}_{\odot}$), Milky Way mass, and low mass ($M_{\star} \sim 10^{9.5} {\rm M}_{\odot}$ ) galaxies appear at $z\sim 4.5$, $z\sim 6.2$, and before $z = 7$. Most quenched galaxies identified at early redshifts remain quenched for more than 1 Gyr. Independently of galaxy stellar mass, the dominant quenching mechanism at high redshift is accretion disk feedback (quasar winds) from a central massive black hole, which is triggered by mergers in massive and MW-mass galaxies, and by disk instabilities in low-mass galaxies. Environmental stripping becomes increasingly more important at lower redshift.

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arXiv2024

Environmental effects on satellite galaxies from the perspective of cold gas

Environment plays a pivotal role in shaping the evolution of satellite galaxies. Analyzing the properties related to the cold gas phase of satellites provides insights into unravelling the complexity of environmental effects. We use the hydro-dynamical simulations Illustris TNG and Eagle, and the semi-analytic models (SAMs) GAEA and L-Galaxies, in comparison with recent observations from the Westerbork Synthesis Radio Telescope (WSRT), to investigate the properties of satellite galaxies hosted by halos with mass $M_{200}>10^{12.8}M_\odot$, and within projected regions $\le 1.1$ virial radius $R_{200}$. Generally, satellite galaxies selected from semi-analytic models have more HI than those selected from hydro-dynamical simulations across all projected radii, e.g. more than 30% of satellites in the two hydro-simulations are HI depleted, while this fraction is almost zero in SAMs. Furthermore, both hydro-dynamical simulations and SAMs reproduce the observed decrease of HI content and specific star-formation rate (sSFR) towards the halo centre. However, the trend is steeper in two hydro-dynamical simulations TNG and EAGLE, resulting in a better agreement with the observational data, especially in more massive halos. By comparing the two version of GAEA, we find that the inclusion of ram-pressure stripping of cold gas significantly improves the predictions on HI fractions. The refined hot gas stripping method employed in one of the two L-Galaxies models also yields improved results.

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arXiv2023

The stellar mass function of quiescent galaxies in 2 < z < 2.5 protoclusters

We present an analysis of the galaxy stellar mass function (SMF) of 14 known protoclusters between $2.0 < z < 2.5$ in the COSMOS field, down to a mass limit of $10^{9.5}$ M$_{\odot}$. We use existing photometric redshifts with a statistical background subtraction, and consider star-forming and quiescent galaxies identified from $(NUV - r)$ and $(r - J)$ colours separately. Our fiducial sample includes galaxies within 1 Mpc of the cluster centres. The shape of the protocluster SMF of star-forming galaxies is indistinguishable from that of the general field at this redshift. Quiescent galaxies, however, show a flatter SMF than in the field, with an upturn at low mass, though this is only significant at $\sim 2σ$. There is no strong evidence for a dominant population of quiescent galaxies at any mass, with a fraction of $< 15\%$ at $1σ$ confidence for galaxies with log$M_{\ast}/M_{\odot} < 10.5$. We compare our results with a sample of galaxies groups at $1 < z < 1.5$, and demonstrate that a significant amount of environmental quenching must take place between these epochs, increasing the relative abundance of high-mass ($\rm M > 10^{10.5} M_{\odot}$) quiescent galaxies by a factor of $\gtrsim$ 2. However, we find that at lower masses ($\rm M < 10^{10.5} M_{\odot}$), no additional environmental quenching is required.

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arXiv2023

When the Well Runs Dry: Modeling Environmental Quenching of High-mass Satellites in Massive Clusters at \boldmath$z \gtrsim 1$

We explore models of massive ($\gt 10^{10}~{\rm M}_{\odot}$) satellite quenching in massive clusters at $z\gtrsim1$ using an MCMC framework, focusing on two primary parameters: $R_{\rm quench}$ (the host-centric radius at which quenching begins) and $τ_{\rm quench}$ (the timescale upon which a satellite quenches after crossing $R_{\rm quench}$). Our MCMC analysis shows two local maxima in the 1D posterior probability distribution of $R_{\rm quench}$ at approximately $0.25$ and $1.0~R_{\rm{200}}$. Analyzing four distinct solutions in the $τ_{\rm quench}$-$R_{\rm quench}$ parameter space, nearly all of which yield quiescent fractions consistent with observational data from the GOGREEN survey, we investigate whether these solutions represent distinct quenching pathways and find that they can be separated between \textquote{starvation} and \textquote{core quenching} scenarios. The starvation pathway is characterized by quenching timescales that are roughly consistent with the total cold gas (H$_{2}$+H{\scriptsize I}) depletion timescale at intermediate $z$, while core quenching is characterized by satellites with relatively high line-of-sight velocities that quench on short timescales ($\sim 0.25$ Gyr) after reaching the inner region of the cluster ($\lt 0.30~R_{\rm{200}}$). Lastly, we break the degeneracy between these solutions by comparing the observed properties of transition galaxies from the GOGREEN survey. We conclude that only the \textquote{starvation} pathway is consistent with the projected phase-space distribution and relative abundance of transition galaxies at $z \sim 1$. However, we acknowledge that ram pressure might contribute as a secondary quenching mechanism.

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arXiv2023

The filament determination depends on the tracer: comparing filaments based on dark matter particles and galaxies in the GAEA semi-analytic model

Filaments are elongated structures that connect groups and clusters of galaxies and are visually the striking feature in cosmological maps. In the literature, typically filaments are defined only using galaxies, assuming that these are good tracers of the dark matter distribution, despite the fact that galaxies are a biased indicator. Here we apply the topological filament extractor DisPerSE to the predictions of the semi-analytic code GAEA to investigate the correspondence between the properties of $z=0$ filaments extracted using the distribution of dark matter and the distribution of model galaxies evolving within the same large-scale structure. We focus on filaments around massive clusters with a mass comparable to Virgo and Coma, with the intent of investigating the influence of massive systems and their feeding filamentary structure on the physical properties of galaxies. We apply different methods to compare the properties of filaments based on the different tracers and study how the sample selection impacts the extraction. Overall, filaments extracted using different tracers agree, although they never coincide totally. We also find that the number of filaments ending up in the massive clusters identified using galaxies distribution is typically underestimated with respect to the corresponding dark matter filament extraction.

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arXiv2023

Massive quiescent galaxies at $z\sim3$: a comparison of selection, stellar population and structural properties with simulation predictions

We study stellar population and structural properties of massive $\log(M_{\star} / M_{\odot}) >11$ galaxies at $z\sim 2.7$ in the Magneticum and IllustrisTNG hydrodynamical simulations and GAEA semi-analytic model. We find stellar mass functions broadly consistent with observations, with no scarcity of massive, quiescent galaxies at $z\sim 2.7$, but with a higher quiescent galaxy fraction at high masses in IllustrisTNG. Average ages of simulated quiescent galaxies are between $\sim 0.8$ and 1.0 Gyr, older by a factor $\sim 2$ than observed in spectroscopically-confirmed quiescent galaxies at similar redshift. Besides being potentially indicative of limitations of simulations in reproducing observed star formation histories, this discrepancy may also reflect limitations in the estimation of observed ages. We investigate the purity of simulated UVJ rest-frame color-selected massive quiescent samples with photometric uncertainties typical of deep surveys (e.g., COSMOS). We find evidence for significant contamination (up to 60 percent) by dusty star-forming galaxies in the UVJ region that is typically populated by older quiescent sources. Furthermore, the completeness of UVJ-selected quiescent samples at this redshift may be reduced by 30 percent due to a high fraction of young quiescent galaxies not entering the UVJ quiescent region. Massive, quiescent galaxies in simulations have on average lower angular momenta and higher projected axis ratios and concentrations than star-forming counterparts. Average sizes of simulated quiescent galaxies are broadly consistent with observations within the uncertainties. The average size ratio of quiescent and star-forming galaxies in the probed mass range is formally consistent with observations, although this result is partly affected by poor statistics.

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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.

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arXiv2023

Early results from GLASS-JWST. XIV: A spectroscopically confirmed protocluster 650 million years after the Big Bang

We present the spectroscopic confirmation of a protocluster at $z=7.88$ behind the galaxy cluster Abell2744 (hereafter A2744-z7p9OD). Using JWST NIRSpec, we find seven galaxies within a projected radius of 60kpc. Although the galaxies reside in an overdensity around $>20\times$ greater than a random volume, they do not show strong Lyman-alpha emission. We place 2-$σ$ upper limits on the rest-frame equivalent width $<16$-$28$AA. Based on the tight upper limits to the Lyman-alpha emission, we constrain the volume-averaged neutral fraction of hydrogen in the intergalactic medium to be $x_{\rm HI} > 0.45$ (68% CI). Using an empirical $M_{\rm UV}$-$M_{\rm halo}$ relation for individual galaxies, we estimate that the total halo mass of the system is $\gtrsim 4\times10^{11}\,M_\odot$. Likewise, the line of sight velocity dispersion is estimated to be $1100 \pm 200$km/s. Using an empirical relation, we estimate the present-day halo mass of A2744-z7p9OD to be $\sim2\times10^{15}\,M_\odot$, comparable to the Coma cluster. A2744-z7p9OD is the highest redshift spectroscopically confirmed protocluster to date, demonstrating the power of JWST to investigate the connection between dark-matter halo assembly and galaxy formation at very early times with medium-deep observations at $<20$hrs total exposure time. Follow-up spectroscopy of the remaining photometric candidates of the overdensity will further refine the features of this system and help characterize the role of such overdensities in cosmic reionization.

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arXiv2023

VST-GAME: Galaxy Assembly as a function of Mass and Environment with VST. Photometric assessment and density field of MACSJ0416

Observational studies have widely demonstrated that galaxy physical properties are strongly affected by the surrounding environment. On one side, gas inflows provide galaxies with new fuel for star formation. On the other side, the high temperatures and densities of the medium are expected to induce quenching in the star formation. Observations of large structures, in particular filaments at the cluster outskirts (r>2r$_{200}$), are currently limited to the low redshift Universe. We present a multi-band dataset for the cluster MACS J0416.1-2403 (z=0.397), observed in the context of the Galaxy Assembly as a function of Mass and Environment with VST (VST-GAME) survey. The project aims at gathering deep ($r$<24.4) and wide (20x20Mpc$^2$) observations at optical wavelengths for six massive galaxy clusters at 0.2<z<0.6, complemented with near infrared data. This work describes the photometric analysis of the cluster, defines a density field and studies galaxy properties in the cluster outskirts. We extract sources paying particular attention to recover the faintest ones. We combine all the extractions in a multi-band catalog and compute photometric redshifts. We then define cluster memberships up to 5r$_{200}$ from the cluster core and measure the density field, comparing galaxy properties in different environments. We found that the $g-r$ colors show bimodal behaviours in all the environments, but the peak of the distribution of red galaxies shifts toward redder colors with increasing density and the fraction of galaxies in the blue cloud increases with decreasing density. We also found 3 overdense regions in the cluster outskirts at r$\sim$5r$_{200}$. The color of galaxies suggests the presence of evolved galaxy populations, an insight for pre-processing phenomena over these substructures. We release the multi-band catalog, down to the completeness limit $r$<24.4 mag.

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arXiv2023

The star formation history and the nature of the mass-metallicity relation of passive galaxies at 1.0<z<1.4 from VANDELS

We derived stellar ages and metallicities [Z/H] for $\sim$70 passive early type galaxies (ETGs) selected from VANDELS survey over the redshift range 1.0$<$$z$$<$1.4 and stellar mass range 10$<$log(M$_*$/M$_\odot$)$<$11.6. We find significant systematics in their estimates depending on models and wavelength ranges considered. Using the full-spectrum fitting technique, we find that both [Z/H] and age increase with mass as for local ETGs. Age and metallicity sensitive spectral indices independently confirm these trends. According to EMILES models, for 67 per cent of the galaxies we find [Z/H]$>$0.0, a percentage which rises to $\sim$90 per cent for log(M$_*$/M$_\odot$)$>$11 where the mean metallicity is [Z/H]=0.17$\pm$0.1. A comparison with homogeneous measurements at similar and lower redshift does not show any metallicity evolution over the redshift range 0.0 $11.0 host stellar populations with [Z/H]>0.05, formed over short timescales ($Δ{t50}$$<$1 Gyr) at early epochs (t$_{form}$$<$2 Gyr), implying high star formation rates (SFR$>$100 M$_\odot$/yr) in high mass density regions (log($Σ_{1kpc}$)$>$10 M$_\odot$/kpc$^2$). This sharp picture tends to blur at lower masses: log(M$_*$/M$_\odot$)$\sim$10.6 galaxies can host either old stars with [Z/H]$<$0.0 or younger stars with [Z/H]$>$0.0, depending on the duration ($Δ{t50}$) of the SF. The relations between galaxy mass, age and metallicities are therefore largely set up ab initio as part of the galaxy formation process. Mass, SFR and SF time-scale all contribute to shape up the stellar mass-metallicity relation with the mass that modulates metals retention.

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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.

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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.

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arXiv2021

H$α$-based Star Formation Rates in and around z $\sim$ 0.5 EDisCS clusters

We investigate the role of environment on star-formation rates of galaxies at various cosmic densities in well-studied clusters. We present the star-forming main sequence for 163 galaxies in four EDisCS clusters in the range 0.4 $<$ z $<$ 0.7. We use {\em Hubble Space Telescope}/Wide Field Camera 3 observations of the H$α$ emission line to span three distinct local environments: the cluster core, infall region, and external field galaxies. The main sequence defined from our observations is consistent with other published H$α$ distributions at similar redshifts, but differs from those derived from star-formation tracers such as 24$μ$m. We find that the H$α$-derived star-formation rates for the 67 galaxies with stellar masses greater than the mass-completeness limit of M$_*>$ 10$^{9.75}$M\textsubscript{$\odot$} show little dependence on environment. At face value, the similarities in the star-formation rate distributions in the three environments may indicate that the process of finally shutting down star formation is rapid, however, the depth of our data and size of our sample make it difficult to conclusively test this scenario. Despite having significant H$α$ emission, 21 galaxies are classified as {\em UVJ}-quiescent and may represent a demonstration of the quenching of star formation caught in the act.

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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.

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