We use HI and H2 global gas measurements of galaxies from xGASS and xCOLD GASS to investigate quenching paths of galaxies below the star formation main sequence (SFMS). We show that the population of galaxies below the SFMS is not a 1:1 match with the population of galaxies below the HI and H2 gas fraction scaling relations. Some galaxies in the transition zone (TZ) 1-sigma below the SFMS can be as HI-rich as those in the SFMS, and have on average longer gas depletion timescales. We find evidence for environmental quenching of satellites, but central galaxies in the TZ defy simple quenching pathways. Some of these so-called "quenched" galaxies may still have significant gas reservoirs and be unlikely to deplete them anytime soon. As such, a correct model of galaxy quenching cannot be inferred with SFR (or other optical observables) alone, but must include observations of the cold gas. We also find that internal structure (particularly, the spatial distribution of old and young stellar populations) plays a significant role in regulating the star formation of gas-rich isolated TZ galaxies, suggesting the importance of bulges in their evolution.
We use the extended GALEX Arecibo SDSS Survey (xGASS) to quantify the relationship between atomic hydrogen (HI) reservoir and current star formation rate (SFR) for central disk galaxies. This is primarily motivated by recent claims for the existence, in this sample, of a large population of passive disks harbouring HI reservoirs as large as those observed in main sequence galaxies. Across the stellar mass range 10$^{9}<$M$_{*}$/M$_{\odot}<$10$^{11}$, we practically find no passive ($\gtrsim$2$σ$ below the star-forming main sequence) disk galaxies with HI reservoirs comparable to those typical …
We present the extended GALEX Arecibo SDSS Survey (xGASS), a gas fraction-limited census of the atomic (HI) gas content of 1179 galaxies selected only by stellar mass ($M_\star =10^{9}-10^{11.5} M_\odot$) and redshift ($0.01<z<0.05$). This includes new Arecibo observations of 208 galaxies, for which we release catalogs and HI spectra. In addition to extending the GASS HI scaling relations by one decade in stellar mass, we quantify total (atomic+molecular) cold gas fractions and molecular-to-atomic gas mass ratios, $R_{mol}$, for the subset of 477 galaxies observed with the IRAM 30 m telescope.…
We present a detailed assessment of the global atomic hydrogen gas fraction in a sample of post-merger galaxies identified in the Sloan Digital Sky Survey (SDSS). Archival HI measurements of 47 targets are combined with new Arecibo observations of a further 51 galaxies. The stellar mass range of the post-merger sample, our observing strategy, detection thresholds and data analysis procedures replicate those of the extended GALEX Arecibo SDSS Survey (xGASS) which can therefore be used as a control sample. Our principal results are: 1) The post-merger sample shows a ~50 per cent higher HI detect…
Context. The xGASS and xCOLD GASS surveys have measured the atomic (HI) and molecular gas (H2) content of a large and representative sample of nearby galaxies (redshift range of 0.01 $\lt$ z $\lt$ 0.05). Aims. We present optical longslit spectra for a subset of the xGASS and xCOLD GASS galaxies to investigate the correlation between radial metallicity profiles and cold gas content. In addition to data from Moran et al. (2012), this paper presents new optical spectra for 27 galaxies in the stellar mass range of 9.0 $\leq$ log Mstar/Msun $\leq$ 10.0. Methods. The longslit spectra were taken alon…
Tracing Quenching in Nearby Galaxies Through Inner Surface Mass Density and Cold Gas Content
Orange Coast College（橙海岸学院）；California Institute of Technology（加州理工学院）；California State University, Long Beach（加州州立大学长滩分校）；University of California, Irvine（加州大学尔湾分校）
We investigate the influence of active galactic nucleus (AGN) feedback on the galaxy cold gas content and its connection to galaxy quenching in three hydrodynamical simulations of Illustris, IllustrisTNG and SIMBA. By comparing to the observed atomic and molecular neutral hydrogen measurements for central galaxies, we find that Illustris over-predicts the cold gas masses in star-forming galaxies and significantly under-predicts them for quenched galaxies. IllustrisTNG performs better in this comparison than Illustris, but quenched galaxies retain too much cold gas compared with observations. S…
One of the key open questions in extragalactic astronomy is what stops star formation in galaxies. While it is clear that the cold gas reservoir, which fuels the formation of new stars, must be affected first, how this happens and what are the dominant physical mechanisms involved is still a matter of debate. At least for satellite galaxies, it is generally accepted that internal processes alone cannot be responsible for fully quenching their star formation, but that environment should play an important, if not dominant, role. In nearby clusters, we see examples of cold gas being removed from …
We determine the cosmic abundance of molecular hydrogen (H2) in the local universe from the xCOLD GASS survey. To constrain the H2 mass function at low masses and correct for the effect of the lower stellar mass limit of 10^9 Msun in the xCOLD GASS survey, we use an empirical approach based on an observed scaling relation between star formation rate and gas mass. We also constrain the HI and HI+H2 mass functions using the xGASS survey, and compare it to the HI mass function from the ALFALFA survey. We find the cosmic abundance of molecular gas in the local Universe to be Omega_H2=(5.34+/-0.47)…
Observations have revealed that disturbances in the cold neutral atomic hydrogen (HI) in galaxies are ubiquitous, but the reasons for these disturbances remain unclear. While some studies suggest that asymmetries in integrated HI spectra (global HI asymmetry) are higher in HI-rich systems, others claim that they are preferentially found in HI-poor galaxies. In this work, we utilise the ALFALFA and xGASS surveys, plus a sample of post-merger galaxies, to clarify the link between global HI asymmetry and the gas properties of galaxies. Focusing on star-forming galaxies in ALFALFA, we find that el…
We investigate the cold-gas properties of massive Virgo galaxies ($>10^9$ M$_\odot$) at $<3R_{200}$ ($R_{200}$ is the radius where the mean interior density is 200 times the critical density) on the projected phase-space diagram (PSD) with the largest archival dataset to date to understand the environmental effect on galaxy evolution in the Virgo cluster. We find: lower HI and H$_2$ mass fractions and higher star-formation efficiencies (SFEs) from HI and H$_2$ in the Virgo galaxies than the field galaxies for matched stellar masses; the Virgo galaxies generally follow the field relationships b…
Previous findings show that the existence of dense cores or bulges is the prerequisite for quenching a galaxy, leading to a proposed two-step quenching scenario: compaction and quenching. In this scenario, galaxies first grow their cores to a stellar mass surface density threshold and subsequently quenching occurs, suggesting that galaxies evolve from extended star-forming galaxies (eSFGs), through compact star-forming galaxies (cSFGs), to quenched population. In this work, we aim at examining the possible evolutionary link between eSFGs and cSFGs by identifying the trends in star formation ra…
Based on well established scaling relation for star forming galaxies as a function of redshift, we argue that the implied growth by a large factor of their angular momentum requires that the angular momentum of the inflowing gas fuelling star formation and disk growth must also secularly increase. We then propose that star formation in disks can cease (quench) once the accreted material (mainly atomic hydrogen) comes in with excessive angular momentum for sustaining an adequate radial flow of cold, molecular gas. Existing observational evidence supporting this scenario is mentioned, together w…
We quantitatively investigate the dependence of central galaxy HI mass ($M_{\rm HI}$) on the stellar mass ($M_\ast$), halo mass ($M_{\rm h}$), star formation rate (SFR), and central stellar surface density within 1 kpc ($Σ_1$), taking advantage of the HI spectra stacking technique using both the Arecibo Fast Legacy ALFA Survey and the Sloan Digital Sky Survey. We find that the shapes of $M_{\rm HI}$-$M_{\rm h}$ and $M_{\rm HI}$-$M_\ast$ relations are remarkably similar for both star-forming and quenched galaxies, with massive quenched galaxies having constantly lower HI masses of around 0.6 de…
In this work, we combine the semi-analytic model of galaxy formation and evolution SAG with the $102$ relaxed simulated galaxy clusters from The Three Hundred project, and we study the link between the quenching of star formation (SF) and the physical processes that galaxies experience through their dynamical history in and around clusters. We classify galaxies in four populations based on their orbital history: recent and ancient infallers, and backsplash and neighbouring galaxies. We find that $\sim 85$ per cent of the current population of quenched galaxies located inside the clusters are a…
We use a semianalytic model of galaxy formation to compare the predictions of two quenching scenarios: halo quenching and black-hole (BH) quenching. After calibrating both models so that they fit the mass function of galaxies, BH quenching is in better agreement with the fraction of passive galaxies as a function of stellar mass $M_*$ and with the galaxy morphological distribution on a star-formation-rate vs. $M_*$ diagram. Besides this main finding, there are two other results from this research. First, a successful BH-quenching model requires that minor mergers contribute to the growth of su…
Neutral Hydrogen in the Shapley Supercluster Core I: Environmental Effects on Gas Content and Galaxy Evolution
Rhodes University（罗德斯大学）；INAF–Istituto di Radioastronomia（意大利国家天体物理研究所射电天文研究所）；INAF–Osservatorio Astronomico di Capodimonte（意大利国家天体物理研究所卡波迪蒙特天文台）；South African Radio Astronomy Observatory（南非射电天文观测台）
MEGATRON: Dwarf Galaxy Quenching in the Epoch of Reionization
University of Sussex（萨塞克斯大学）；DISCnet Centre for Doctoral Training, University of Sussex（萨塞克斯大学 DISCnet 博士培训中心）；University of Bath（巴斯大学）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；Institut d’Astrophysique de Paris, Sorbonne Université, CNRS（巴黎天体物理研究所，索邦大学，法国国家科学研究中心）；University of Oxford（牛津大学）
We use the semi-analytic model of galaxy formation SAG to study the relevance of mass and environmental quenching on satellite galaxies. We find that environmental processes dominate the star formation (SF) quenching of low-mass satellites ($M_{\star} \lesssim 10^{10.5}\, {\rm M}_{\odot}$), whereas high-mass galaxies typically quench as centrals. High-mass galaxies that remain actively forming stars while being accreted are found to be mainly affected by mass quenching after their first infall. For a given stellar mass, our model predicts SF quenching to be less efficient in low-mass haloes bo…
We compile a sample of SDSS galaxy clusters with high-quality Chandra X-ray data to directly study the influence of the dense intra-cluster medium (ICM) on the quenching of satellite galaxies. We study the quenched fractions of satellite galaxies as a function of ICM density for low- ($10^9 \lesssim M_\star \lesssim 10^{10}\,\mathrm{M_\odot}$), intermediate- ($10^{10} \lesssim M_\star \lesssim 10^{10.5}\,\mathrm{M_\odot}$), and high-mass ($M_\star \gtrsim 10^{10.5}\,\mathrm{M_\odot}$) satellite galaxies with $>\!3000$ satellite galaxies across 24 low-redshift ($z < 0.1$) clusters. For low-mass…
Investigating quenching in Recently Quenched Elliptical galaxies with HI studies
University of Missouri-Kansas City（密苏里大学堪萨斯城分校）；Arecibo Observatory, NAIC（阿雷西博天文台，北美星际与电离层中心）；University of Minnesota, Twin Cities（明尼苏达大学双城分校）；National Centre for Radio Astrophysics, Tata Institute of Fundamental Research（国家射电天体物理中心，塔塔基础研究所）
(Abridged) We explore 7 clusters from LoCuSS at z~0.2 with spectra of 1965 cluster members from the ACReS Hectospec survey covering a region which corresponds to about three virial radii for each cluster. We measure fluxes of five emission lines of cluster members enabling us to unambiguously derive O/H gas metallicities, and also SFRs from extinction corrected Halpha fluxes. We compare our cluster galaxy sample with a field sample of 705 galaxies at similar redshifts observed with Hectospec. We find that star-forming cluster and field galaxies show similar median specific SFRs in a given mass…
We investigate how large-scale cosmic filaments impact the quenching of galaxies within one virial radius of 324 simulated clusters from The Three Hundred project. We track cosmic filaments with the versatile, observation-friendly program DisPerSE and identify halos hosting galaxies with VELOCIRaptor. We find that cluster galaxies close to filaments tend to be more star-forming, bluer, and contain more cold gas than their counterparts further away from filaments. This effect is recovered at all stellar masses. This is in stark contrast with galaxies residing outside of clusters, where galaxies…
Dust and PAHs in late-stage galaxy evolution: Imprints of TP-AGB dust injection, grain growth and AGN feedback in high-z quiescent galaxies with JWST and ALMA
National Center for Nuclear Research（国家核研究中心）；SISSA（的里雅斯特国际高等研究学院）；INAF, Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；INAF - Osservatorio Astronomico d’Abruzzo（意大利国家天体物理研究所阿布鲁佐天文台）；Department of Astronomy, University of Massachusetts, Amherst（马萨诸塞大学阿默斯特分校天文学系）；Cosmic Dawn Center (DAWN)（宇宙黎明中心）；Department of Physics & Astronomy, University of British Columbia（不列颠哥伦比亚大学物理与天文学系）；Caltech/IPAC（加州理工学院/IPAC）；IFPU – Institute for Fundamental Physics of the Universe（基础物理学宇宙研究所）；Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Center for Astrophysics and Cosmology, University of Nova Gorica（新戈里察大学天体物理学与宇宙学中心）
The quenching "maintenance'" and related "cooling flow" problems are important in galaxies from Milky Way mass through clusters. We investigate this in halos with masses $\sim 10^{12}-10^{14}\,{\rm M}_{\odot}$, using non-cosmological high-resolution hydrodynamic simulations with the FIRE-2 (Feedback In Realistic Environments) stellar feedback model. We specifically focus on physics present without AGN, and show that various proposed "non-AGN" solution mechanisms in the literature, including Type Ia supernovae, shocked AGB winds, other forms of stellar feedback (e.g. cosmic rays), magnetic fiel…
Using the EAGLE suite of simulations, we demonstrate that both cold gas stripping {\it and} starvation of gas inflow play an important role in quenching satellite galaxies across a range of stellar and halo masses, $M_{\star}$ and $M_{200}$. By quantifying the balance between gas inflows, outflows, and star formation rates, we show that even at $z=2$, only $\approx30\%$ of satellite galaxies are able to maintain equilibrium or grow their reservoir of cool gas - compared to $\approx50\%$ of central galaxies at this redshift. We find that the number of orbits completed by a satellite is a very g…
The massive galaxy population above the characteristic Schechter mass M*~10^10.6 Msun contributes to about half of the total stellar mass in the local Universe. These massive galaxies usually reside in hot dark matter haloes above the critical shock-heating mass ~10^12 Msun, where the external cold gas supply to these galaxies is expected to be suppressed. When galaxies run out of their cold gas reservoir, they become dead and quiescent. Therefore, massive quiescent galaxies living in hot haloes are commonly believed to be gas-poor. Based on the data from SDSS, ALFALFA, GASS and COLD GASS surv…
The goal of the Local Cluster Survey is to look for evidence of environmentally driven quenching among star-forming galaxies in nearby galaxy groups and clusters. Quenching is linked with environment and stellar mass, and much of the current observational evidence comes from the integrated properties of galaxies. However, the relative size of the stellar and star-forming disk is sensitive to environmental processing and can help identify the mechanisms that lead to a large fraction of quenched galaxies in dense environments. Toward this end, we measure the size of the star-forming disks for 22…
In this work, we analyze the role of AGN feedback in quenching star formation for massive, central galaxies in the local Universe. In particular, we compare the prediction of two semi-analytic models (L-GALAXIES and SAGE) featuring different schemes for AGN feedback, with the SDSS DR7 taking advantage of a novel technique for identifying central galaxies in an observational dataset. This enables us to study the correlation between the model passive fractions, which is predicted to be suppressed by feedback from an AGN, and the observed passive fractions in an observationally motivated paramete…
We study the abundance of star-forming and quiescent galaxies in a sample of 21 massive clusters at 0.5<z<0.7, detected with the Planck satellite. We measure the cluster galaxy stellar mass function (SMF), which is a fundamental observable to study and constrain the formation and evolution of galaxies. Our measurements are based on homogeneous and deep multi-band photometry spanning u- to the Ks-band for each cluster and are supported by spectroscopic data from different programs. The galaxy population is separated between quiescent and star-forming galaxies based on their rest-frame U-V and V…
We investigate the influence of environment on the cold-gas properties of galaxies at z=0 within the TNG100 cosmological, magnetohydrodynamic simulation, part of the IllustrisTNG suite. We extend previous post-processing methods for breaking gas cells into their atomic and molecular phases, and build detailed mocks to comprehensively compare to the latest surveys of atomic hydrogen (HI) in nearby galaxies, namely ALFALFA and xGASS. We use TNG100 to explore the HI content, star formation activity, and angular momentum of satellite galaxies, each as a function of environment, and find that satel…
Reproducing the observed quenched fraction of satellite galaxies has been a long-standing issue for galaxy formation models. We modify the treatment of environmental effects in our state-of-the-art GAlaxy Evolution and Assembly (GAEA) semi-analytic model to improve our modelling of satellite galaxies. Specifically, we implement gradual stripping of hot gas, ram-pressure stripping of cold gas, and an updated algorithm to account for angular momentum exchanges between the gaseous and stellar disc components of model galaxies. Our updated model is in good agreement with the observed quenched frac…
Massive quiescent compact galaxies have been discovered at high redshifts, associated with rapid compaction and cessation of star formation (SF). In this work we set out to quantify the time-scales in which SF is quenched in compact galaxies at intermediate redshifts. For this, we select a sample of green valley galaxies within the COSMOS field in the midst of quenching their SF at $0.5<z<1.0$ that exhibit varying degrees of compactness. Based on the H$δ$ absorption line and the 4000 Å\ break of coadded zCOSMOS spectra for sub-samples of normal-sized and compact galaxies we determine quenching…
Galactic bars can affect the evolution of galaxies by redistributing gas in galaxies, possibly contributing to the cessation of star formation. Recent works point to 'bar quenching' playing an important role in massive disk galaxies like the Milky Way. We construct the largest ever sample of gas rich and strongly barred disc galaxies with resolved HI observations making use of both the Giant Meter Radio Telescope (GMRT) and the Karl Jansky Very Large Array (VLA) to collect data. This sample, called HIRB (HI Rich Barred) galaxies, were identified with Galaxy Zoo - to find galaxies hosting a str…
Caught in the act: gas and stellar velocity dispersions in a fast quenching compact star-forming galaxy at z~1.7
我们介绍了GDN-8231的Y和H波段的Mask-I MOSFIRE光谱，GDN-8231是一个大质量、致密的恒星形成星系（SFG），红移为$z\sim1.7$。它的光谱揭示了H $_α$和[NII]发射线以及强的巴耳末吸收线。H $_α$和斯皮策MIPS 24 $μ$ m通量都很弱，因此表明SFR $\lesssim5-10$ M $_{\odot}$ yr $^{-1}$的恒星形成率很低。再加上从吸收线测量到的$\sim700$ Myr相对年轻的年龄，这为遥远的星系在快速关闭其恒星形成过程中被捕获提供了第一个直接证据。这样的淬灭使得GDN-8231成为一个紧凑的，静止的星系，类似于我们样本中的其他3个星系，通过$z\sim1.5$。此外，GDN-8231的颜色分布显示出更蓝的中心，与最近模拟的由内而外淬灭早期阶段的预测一致。它的气体视线速度色散$σ^{\rm{gas}}_{\!_{\rm LOS}}=127\pm32$ km s $^{-1}$比它的恒星$σ^{\star}_{\!_{\rm LOS}}=215\pm35$ km s $^{-1}$小近40%。星系的高分辨率流体模拟解释了这种明显较冷的气体运动学的$\sim1.5$的一个因素与旋转盘被认为是在不同的倾角和/或集中的恒星形成区域。一个明确的预测是，它们紧凑、静止的后代保留了一些来自恒星形成祖先的残余旋转。
