Today, the brightest cluster galaxies (BCGs) are passive and very massive galaxies at the center of their clusters, and they still accrete mass through swallowing companions and gas from cooling flows. However their formation history is not well known. We report CO(4$\rightarrow$3) and continuum map observations of the SpARCS1049+56 BCG at $z=1.709$, one of the most distant known BCGs. Our observations yield $M_{{\rm H}_2}<1.1\times10^{10}M_\odot$ for the BCG; while in CO(4$\rightarrow$3), we detect two gas-rich companions at the northeast and southeast of the BCG, within 20 kpc, with ${L^\prime_{\rm CO(4\rightarrow3)}=(5.8\pm0.6)\times10^{9}}$ K km s$^{-1}$ pc$^2$ and $(7.4\pm0.7)\times10^{9}$ K km s$^{-1}$ pc$^2$, respectively. The northern companion is associated with a pair of merging cluster galaxies, while the southern one shows a southern tail in CO(4$\rightarrow$3), which was also detected in continuum, and we suggest it to be the most distant jellyfish galaxy for which ram pressure stripping is effectively able to strip off its dense molecular gas. This study probes the presence of rare gas-rich systems in the very central region of a distant cluster core, which will potentially merge into the BCG itself. Currently, we may thus be seeing the reversal of the star formation versus density relation at play in the distant universe. This is the first time the assembly of high-$z$ progenitors of our local BCGs can be studied in such great detail.
Aims. We investigate the environmental dependence of the stellar mass fundamental plane (FP$_*$) using the early-type galaxy sample from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Methods. The FP$_*$ is calculated by replacing the luminosity in the fundamental plane (FP) with stellar mass. Based on the SDSS group catalog, we characterize the galaxy environment according to the mass of the host dark matter halo and the position in the halo. In halos with the same mass bin, the color distributions of central and satellite galaxies are different. Therefore, we calculate FP$_*$ coeffi…
We study the galaxy alignment in the sample of very rich Abell clusters located in and outside superclusters. The statistically significant difference among investigated samples exists. We found that in contrast to whole sample of cluster, where alignment increase with the cluster richness, the cluster belonging to the superclusters does not show this effect. Moreover, the alignment decreased with the supercluster richness. One should note however that orientations of galaxies in analyzed clusters are not random, both in the case when we analyzed whole sample of the clusters and only clusters …
We present a multiwavelength study of galaxies around D4UD01, a spectroscopically confirmed protocluster at z = 3.24 to investigate environmental trends. 450 galaxies are selected based on Ks band detection with photometric redshifts (photo-z) at 3.0 < z < 3.4, among which ~ 12% are classified as quiescent galaxies. The quiescent galaxies are among the most massive and reddest ones in the entire sample. We identify a large photo-z galaxy overdensity in the field, which lies close to the previously spectroscopically confirmed sources of the protocluster. We find that the quiescent galaxies are …
Within the standard model of hierarchical galaxy formation in a ΛCDM Universe, the environment of galaxies is expected to play a key role in driving galaxy formation and evolution. In this paper we investigate whether and how the gas metallicity and the star formation surface density (Σ_SFR) depend on galaxy environment. To this end we analyse a sample of 1162 local, star-forming galaxies from the galaxy survey Mapping Nearby Galaxies at APO (MaNGA). Generally, both parameters do not show any significant dependence on environment. However, in agreement with previous studies, we find that low-m…
We explore the variation in stellar population ages for Coma cluster galaxies as a function of projected cluster-centric distance, using a sample of 362 red-sequence galaxies with high signal-to-noise spectroscopy. The sample spans a wide range in luminosity (0.02-4 L*) and extends from the cluster core to near the virial radius. We find a clear distinction in the observed trends of the giant and dwarf galaxies. The ages of red-sequence giants are primarily determined by galaxy mass, with only weak modulation by environment, in the sense that galaxies at larger cluster-centric distance are sli…
We present a variation of the recently updated Munich semi-analytical galaxy formation model, L-Galaxies, with a new gas stripping method. Extending earlier work, we directly measure the local environmental properties of galaxies to formulate a more accurate treatment of ram-pressure stripping for all galaxies. We fully re-calibrate the modified L-Galaxies model using a Markov Chain Monte Carlo (MCMC) method with the stellar mass function and quenched fraction of galaxies at $0\leq z\leq2$ as constraints. Due to this re-calibration, global galaxy population relations, including the stellar mas…
We analyze the SDSS data to classify the galaxies based on their colour using a fuzzy set-theoretic method and quantify their environments using the local dimension. We find that the fraction of the green galaxies does not depend on the environment and $10\%-20\%$ of the galaxies at each environment are in the green valley depending on the stellar mass range chosen. Approximately $10\%$ of the green galaxies at each environment host an AGN. Combining data from the Galaxy Zoo, we find that $\sim 95\%$ of the green galaxies are spirals and $\sim 5\%$ are ellipticals at each environment. Only $\s…
In the Local Group, nearly all of the dwarf galaxies (M_star < 10^9 M_sun) that are satellites within 300 kpc (the virial radius) of the Milky Way (MW) and Andromeda (M31) have quiescent star formation and little-to-no cold gas. This contrasts strongly with comparatively isolated dwarf galaxies, which are almost all actively star-forming and gas-rich. This near dichotomy implies a rapid transformation of satellite dwarf galaxies after falling into the halos of the MW or M31. We combine the observed quiescent fractions for satellites of the MW and M31 with the infall times of satellites from th…
Using a sample of 70,793 early-type galaxies from SDSS DR7, we study the environmental dependence of the fundamental plane relation. With the help of the galaxy group catalogue based on SDSS DR7, we calculate the fundamental planes in different dark matter halo mass bins for central and satellite galaxies respectively. We find the environmental dependence of the fundamental plane coefficients are similar in $g$, $r$, $i$ and $z$ bands. The environmental dependence for central and satellite galaxies is significantly different. While the fundamental plane coefficients of centrals vary systematic…
We combine ultraviolet to near-infrared photometry with HI 21cm line observations for a complete volume-limited sample of nearby galaxies in different environments (from isolated galaxies to Virgo cluster members), to study the migration of spirals from the blue to the red sequence. Although our analysis confirms that, in the transition region between the two sequences, a high fraction of spirals host active galactic nuclei (AGN), it clearly shows that late-types with quenched star formation are mainly HI deficient galaxies preferentially found in the Virgo cluster. This not only suggests that…
Quantifying Environmental Effects on Galaxy Properties using Non-spherical Voids Identified from SDSS DR7
Shanghai Jiao Tong University（上海交通大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；University of Chinese Academy of Sciences（中国科学院大学）
To understand the role of the environment in galaxy formation, evolution, and present-day properties, it is essential to study the multi-frequency behavior of different galaxy populations under various environmental conditions. We crossmatch the SDSS DR10 group catalog with GAMA Data Release 2 and Wide-field Survey Explorer (WISE) data to construct a catalog of 1651 groups and 11436 galaxies containing photometric information in 15 different wavebands ranging from ultraviolet (0.152 μm) to mid-infrared (22 μm). We perform the spectral energy distribution (SED) fitting of galaxies using the MAG…
SubHalo Abundance Matching (SHAM) assumes that one (sub)halo property, such as mass Mvir or peak circular velocity Vpeak, determines properties of the galaxy hosted in each (sub)halo such as its luminosity or stellar mass. This assumption implies that the dependence of Galaxy Luminosity Functions (GLFs) and the Galaxy Stellar Mass Function (GSMF) on environmental density is determined by the corresponding halo density dependence. In this paper, we test this by determining from an SDSS sample the observed dependence with environmental density of the ugriz GLFs and GSMF for all galaxies, and for…
Galaxies that are several virial radii beyond groups/clusters show preferentially quiescent star formation rates. Using a galaxy group/cluster catalog from the Sloan Digital Sky Survey, together with a cosmological N-body simulation, we examine the origin of this environmental quenching beyond the virial radius. Accounting for the clustering of groups/clusters, we show that central galaxies show enhanced SFR quenching out to 2.5 virial radii beyond groups/clusters, and we demonstrate that this extended environmental enhancement can be explained simply by 'ejected' satellite galaxies that orbit…
We present a novel application of the extended Fast Action Minimization method (eFAM) aimed at assessing the role of the environment in shaping galaxy evolution. We validate our approach by testing eFAM predictions against the Magneticum hydrodynamical simulation. We consider the z~0 snapshot of the simulation as our observed catalogue and use the reconstructed trajectories of galaxies to model the evolution of cosmic structures. At the statistical level, the fraction of volume (VFF) occupied by voids, sheets, filaments, and clusters in the reconstructed catalogues agrees within $1σ$ with the …
This work presents the results from our near-infrared spectroscopy of narrow-band selected H$α$ emitters (HAEs) in two rich over-densities (PKS 1138-262 at $z=2.2$ and USS 1558-003 at $z=2.5$) with the Multi-Object Infrared Camera and Spectrograph (MOIRCS) on the Subaru telescope. These protoclusters are promising candidates for the most massive class of galaxy clusters seen today (Paper I). The confirmed HAEs in the protoclusters at $z>2$ show high excitation levels as characterized by much higher [OIII]/H$β$ or [OIII]/H$α$ line ratios than those of general galaxies at low-$z$. Such a high ex…
We present direct observational evidence for star formation quenching in galaxy groups in the redshift range 0<z<2.5. We utilize a large sample of nearly 6000 groups, selected by fixed cumulative number density from three photometric catalogs, to follow the evolving quiescent fractions of central and satellite galaxies over roughly 11 Gyr. At z~0, central galaxies in our sample range in stellar mass from Milky Way/M31 analogs (M=6.5x10^10 M\solar) to nearby massive ellipticals (M=1.5x10^11 M\solar). Satellite galaxies in the same groups reach masses as low as twice that of the Large Magellanic…
We investigate the environmental dependence of the stellar populations of galaxies in SDSS DR7. Echoing earlier works, we find that satellites are both more metal-rich (<0.1 dex) and older (<2 Gyr) than centrals of the same stellar mass. However, after separating star-forming, green valley and passive galaxies, we find that the true environmental dependence of both stellar metallicity (<0.03 dex) and age (<0.5 Gyr) is in fact much weaker. We show that the strong environmental effects found when galaxies are not differentiated result from a combination of selection effects brought about by the …
Under the $Λ$ cold dark matter ($Λ$CDM) cosmological models, massive galaxies are expected to be larger in denser environments through frequent hierarchical mergers with other galaxies. Yet, observational studies of low-redshift early-type galaxies have shown no such trend, standing as a puzzle to solve during the past decade. We analyzed 73,116 early-type galaxies at $0.1\leq z < 0.15$, adopting a robust nonparametric size measurement technique and extending the analysis to many massive galaxies. We find for the first time that local early-type galaxies heavier than $10^{11.2}M_{\odot}$ show …
We measure the radial profiles of the stellar velocity dispersions, $σ(R)$, for 90 early-type galaxies (ETGs) in the MASSIVE survey, a volume-limited integral-field spectroscopic (IFS) galaxy survey targeting all northern-sky ETGs with absolute $K$-band magnitude $M_K < -25.3$ mag, or stellar mass $M_* > 4 \times 10^{11} M_\odot$, within 108 Mpc. Our wide-field 107" $\times$ 107" IFS data cover radii as large as 40 kpc, for which we quantify separately the inner (2 kpc) and outer (20 kpc) logarithmic slopes $γ_{\rm inner}$ and $γ_{\rm outer}$ of $σ(R)$. While $γ_{\rm inner}$ is mostly negative…
One of the challenges in understanding the quenching processes for galaxies is connecting progenitor star-forming populations to their descendant quiescent populations over cosmic time. Here we attempt a novel approach to this challenge by assuming that the underlying stellar mass distribution of galaxies is not significantly altered during environmental quenching processes that solely affect the gas content of cluster galaxies, such as strangulation and ram-pressure stripping. Using the deep, high-resolution photometry of the Hubble Frontier Fields, we create resolved stellar mass maps for bo…
We use the Zurich ENvironmental Study (ZENS) database to investigate the environmental dependence of the merger fraction $Γ$ and merging galaxy properties in a sample of ~1300 group galaxies with $M>10^{9.2}M_\odot$ and 0.05<z<0.0585. In all galaxy mass bins investigated in our study, we find that $Γ$ decreases by a factor of ~2-3 in groups with halo masses $M_{HALO}>10^{13.5} M_\odot$ relative to less massive systems, indicating a suppression of merger activity in large potential wells. In the fiducial case of relaxed groups only, we measure a variation $ΔΓ/Δ\log (M_{HALO}) \sim - 0.07$ dex$^…
We review numerical work carried out over the last decade on the role of environmental mechanisms in shaping the nature of the faintest galaxies known, dwarf spheroidals (dSphs). In particular we discuss a model in which dSphs originated from gas dominated, disky dwarfs that were accreted by massive galaxies several billions of years ago. Dwarfs accreting at $z > 1$, when the cosmic ultraviolet ionizing flux was much higher than today and was thus able to keep the gas in the dwarfs warm and diffuse, were rapidly stripped of their baryons via ram pressure and tidal forces, producing very dark m…
We present a detailed analysis of the influence of the environment and of the environmental history on quenching star formation in central and satellite galaxies in the local Universe. We take advantage of publicly available galaxy catalogues obtained from applying a galaxy formation model to the Millennium simulation. In addition to halo mass, we consider the local density of galaxies within various fixed scales. Comparing our model predictions to observational data (SDSS), we demonstrate that the models are failing to reproduce the observed density dependence of the quiescent galaxy fraction…
Molecular hydrogen (H2) is the primary component of the reservoirs of cold, dense gas that fuel star formation in our galaxy. While the H2 abundance is ultimately regulated by physical processes operating on small scales in the interstellar medium (ISM), observations have revealed a tight correlation between the ratio of molecular to atomic hydrogen in nearby spiral galaxies and the pressure in the mid-plane of their disks. This empirical relation has been used to predict H2 abundances in galaxies with potentially very different ISM conditions, such as metal-deficient galaxies at high redshift…
The role played by the large-scale structures in the galaxy evolution is not quite well understood yet. In this study, we investigate properties of galaxy in the range 0.1<z<0.3 from a value-added version of the WISExSCOS catalogue around cosmic filaments detected with DisPerSE. We have fitted a profile of galaxy over-density around cosmic filaments and found a typical radius of r_m = 7.5+-0.2 Mpc. We have measured an excess of passive galaxies near the filament's spine, higher than the excess of transitioning and active galaxies. We have also detected SFR and Mstar gradients pointing towards …
Using a stellar mass limited sample of $\sim 46,600$ galaxies ($M_* > 10^{9.1}\,M_{\odot}$) at $0.5 < z < 2$, we show that the tellar mass, rather than the environment, is the main parameter controlling quenching of star formation in galaxies with $M_* > 10^{10}\,M_{\odot}$ out to $z=2$. On the other hand, the environmental quenching becomes efficient at $z < 1$ regardless of galaxy mass, and it serves as a main star formation quenching mechanism for lower mass galaxies. Our result is based on deep optical and near-infrared imaging data over 2800 arcmin$^2$, enabling us to negate cosmic varian…
We report the discovery of a strong over-density of galaxies in the field of a radio galaxy at z=1.52 (4C65.22) based on our broad-band and narrow-band (H-alpha) photometry with Subaru Telescope. We find that H-alpha emitters are located in the outskirts of the density peak (cluster core) dominated by passive red-sequence galaxies. This resembles the situation in lower-redshift clusters, suggesting that the newly discovered structure is a well-evolved rich galaxy cluster at z=1.5. Our data suggest that the color-density and stellar mass-density relations are already in place at z~1.5, mostly d…
Environmental history of filament galaxies: stellar mass assembly and star-formation of filament galaxies
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）；IFPU - Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；INAF – Osservatorio astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；Tianjin Normal University（天津师范大学）
We explore properties of close galaxy pairs and merging systems selected from the SDSS-DR4 in different environments with the aim to assess the relative importance of the role of interactions over global environmental processes. For this purpose, we perform a comparative study of galaxies with and without close companions as a function of local density and host-halo mass, carefully removing sources of possible biases. We find that at low and high local density environments, colours and morphologies of close galaxy pairs are very similar to those of isolated galaxies. At intermediate densities,…
By combining H$α$ flux measurements from the Sloan Digital Sky Survey (SDSS) with UV flux observations from the Galaxy Evolution Explorer (GALEX), we examine the environmental dependence (through central/satellite distinction) of the rapid quenching and rejuvenation of galaxies. H$α$ emissions trace the most massive stars, thereby indicating star-formation on timescales of $\sim 10$ Myr, while UV emission traces star-formation on timescales of $\sim 100$ Myr. These varying timescales are exploited to probe the most recent star-formation histories of galaxies. In this work, we define a class of…
We discuss the environment of local hard X-ray selected active galaxies, with reference to two independent group catalogues. We find that the fraction of these AGN in S0 host galaxies decreases strongly as a function of galaxy group size (halo mass) - which contrasts with the increasing fraction of galaxies of S0 type in denser environments. However, there is no evidence for an environmental dependence of AGN in spiral galaxies. Because most AGN are found in spiral galaxies, this dilutes the signature of environmental dependence for the population as a whole. We argue that the differing result…
We measure the environmental dependence, where environment is defined by the distance to the third nearest neighbor, of multiple galaxy properties inside the Environmental COntext (ECO) catalog. We focus primarily on void galaxies, which we define as the $10 \%$ of galaxies having the lowest local density. We compare the properties of void and non-void galaxies: baryonic mass, color, fractional stellar mass growth rate (FSMGR), morphology, and gas-to-stellar-mass ratio (estimated from a combination of HI data and photometric gas fractions calibrated with the RESOLVE survey). Our void galaxies …
Environmental Sculpting of Galaxy Structure at Fixed Stellar Mass: A Multi-Scale Analysis Across Cosmic Time using 3 Million HSC Galaxies
University of Washington（华盛顿大学）；DiRAC Institute, University of Washington（华盛顿大学迪拉克研究所）；eScience Institute, University of Washington（华盛顿大学eScience研究所）；Department of Astronomy and Astrophysics, University of California, Santa Cruz（加州大学圣克鲁兹分校天体物理与天文学系）；Yale Center for Astronomy and Astrophysics（耶鲁天体物理中心）；Department of Physics, Yale University（耶鲁大学物理系）；Department of Physics, California Polytechnic State University（加州州立理工大学物理系）；Waseda Institute for Advanced Study (WIAS), Waseda University（早稻田大学高等研究院）
Galaxies that have fallen into massive haloes may no longer be able to accrete gas from their surroundings, a process referred to as 'starvation' or 'strangulation' of satellites. We study the environmental dependence of gas accretion onto galaxies using the cosmological, hydrodynamical EAGLE simulation. We quantify the dependence of gas accretion on stellar mass, redshift, and environment, using halo mass and galaxy overdensity as environmental indicators. We find a strong suppression, by many orders of magnitude, of the gas accretion rate in dense environments, primarily for satellite galaxi…
We study the quenching of star formation as a function of redshift, environment and stellar mass in the galaxy formation simulations of Henriques et al. (2015), which implement an updated version of the Munich semi-analytic model (L-GALAXIES) on the two Millennium Simulations after scaling to a Planck cosmology. In this model massive galaxies are quenched by AGN feedback depending on both black hole and hot gas mass, and hence indirectly on stellar mass. In addition, satellite galaxies of any mass can be quenched by ram-pressure or tidal stripping of gas and through the suppression of gaseous …
The connection between galaxy star formation rate (SFR) and dark matter (DM) is of paramount importance for the extraction of cosmological information from next generation spectroscopic surveys that will target emission line star forming galaxies. Using publicly available mock galaxy catalogs obtained from various semi-analytic models (SAMs) we explore the SFR-DM connection in relation to the speed-from-light method (Feix et al. 2016) for inferring the growth rate, $f$, from luminosity/SFR shifts. Emphasis is given to the dependence of the SFR distribution on the environment density on scales …
A model is proposed for the formation of gas-rich dwarf irregular galaxies and gas-poor, rotating dwarf elliptical galaxies following the interaction between two giant galaxies as a function of space density. The formation of dwarf galaxies is considered to depend on a random variable, the tidal index theta, an environmental parameter defined by Karachentsev et al. (2004), such that for theta less than zero, the formation of dwarf irregular galaxy is assured whereas for theta greater than zero, the formation of dwarf ellipticals is preferred. It is found that for particular ranges of the inter…
We present infrared views of the environmental effects on the dust properties in star-forming (SF) galaxies at z ~ 0, using the AKARI Far-Infrared Surveyor (FIS) all-sky map and the large spectroscopic galaxy sample from Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We restrict the sample to those within the redshift range of 0.05 < z < 0.07 and the stellar mass range of 9.2 < log_10 (M_star/M_solar). We select SF galaxies based on their H_alpha equivalent width (EW_Ha> 4 A) and emission line flux ratios. We perform far-infrared (FIR) stacking analyses by splitting the SDSS SF galaxy s…
We present the results from ALMA CO(3-2) observations of 66 Halpha-selected galaxies in three protoclusters around radio galaxies, PKS1138-262 (z=2.16) and USS1558-003 (z=2.53), and 4C23.56 (z=2.49). The pointing areas have an overdensity of ~100 compared to a mean surface number density of galaxies in field environments. We detect CO emission line in 16 star-forming galaxies, including previously published six galaxies, to measure the molecular gas mass. In the stellar mass range of 10.5<log(Mstar/Msolar)<11.0, the protocluster galaxies have larger gas mass fractions and longer gas depletion …
We present and explore the resolved atomic hydrogen (HI) content of 13 HI-rich and late-type dominated groups denoted `Choirs'. We quantify the HI content of the Choir galaxies with respect to the median of the HI-mass fraction ($f_{\textrm{HI}}$) of their grandparent HIPASS sample. We find that the HI mass fraction of the Choir galaxies is dispersed around the HIPASS median in the range $-1.4 \leq Δf_{\textrm{HI}}\textrm{[dex]}\leq 0.7$, from HI-excess to HI-deficient galaxy regime. The HI-excess/HI-deficient galaxies contain more/less than 2.5 times their expected HI content with respect to …
We explore the dependence of UV upturn colours in early type cluster galaxies on the properties of their parent clusters (such as velocity dispersion and X-ray luminosity) and on the positions and kinematics of galaxies within them. We use a sample of 24 nearby clusters with highly complete spectroscopy and optical/infrared data to select a suitable sample of red sequence galaxies, whose FUV and NUV magnitudes we measure from archival GALEX data. Our results show that the UV upturn colour has no dependence on cluster properties and has the same range in all clusters. There is also no dependenc…
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 $1.0<z<1.4$ from the GOGREEN sample. We identify three different types of transition galaxies: "green valley" (GV) galaxies identified from their rest-frame $(NUV-V)$ and $(V-J)$ colours; "blue quiescent" (BQ) galaxies, found at the blue end of the quiescent sequence in $(U-V)$ and $(V-J)$ colour; and spectroscopic post-starburst (PSB) galaxies. We measure the abundance of these galaxies as …
We investigate environmental effects on galaxy spin using the recent public data of MaNGA integral field spectroscopic survey containing ~2800 galaxies. We measure the spin parameter of 1830 galaxies through the analysis of two-dimensional stellar kinematic maps within the effective radii, and obtain their large- (background mass density from 20 nearby galaxies) and small-scale (distance to and morphology of the nearest neighbour galaxy) environmental parameters for 1529 and 1767 galaxies, respectively. We first examine the mass dependence of galaxy spin, and find that the spin parameter of ea…
The environment within dark matter haloes can quench the star formation of galaxies. However, environmental effects beyond the virial radius of haloes ($\gtrsim$ 1 Mpc) are less evident. An example is the debated correlation between colour or star formation in central galaxies and neighbour galaxies in adjacent haloes at large separations of several Mpc, referred to as two-halo galactic conformity. We use two galaxy catalogues generated from different versions of the semi-analytic model SAG applied to the MDPL2 cosmological simulation and the IllustrisTNG300 cosmological hydrodynamical simulat…
We present a study of the star formation and AGN activity for galaxies in the Abell 901/2 multi-cluster system at z~0.167 as part of the OMEGA survey. Using Tuneable Filter data obtained with the OSIRIS instrument at the GTC we produce spectra covering the Halpha and [N II] spectral lines for more than 400 galaxies. Using optical emission-line diagnostics, we identify a significant number of galaxies hosting AGN, which tend to have high masses and a broad range of morphologies. Moreover, within the environmental densities probed by our study, we find no environmental dependence on the fraction…
We report evidence of environmental quenching among galaxies at redshift ~ 2, namely the probability that a galaxy quenches its star formation activity is enhanced in the regions of space in proximity of other quenched, more massive galaxies. The effect is observed as strong clustering of quiescent galaxies around quiescent galaxies on angular scales θ< 20 arcsec, corresponding to a proper(comoving) scale of 168 (502) kpc at z = 2. The effect is observed only for quiescent galaxies around other quiescent galaxies; the probability to find star-forming galaxies around quiescent or around star-fo…
We present new analysis from the GEEC2 spectroscopic survey of galaxy groups at $0.8<z<1$. Our previous work revealed an intermediate population between the star-forming and quiescent sequences and a strong environmental dependence in the fraction of quiescent galaxies. Only $\sim5$ per cent of star-forming galaxies in both the group and field sample show a significant enhancement in star formation, which suggests that quenching is the primary process in the transition from the star-forming to the quiescent state. To model the environmental quenching scenario, we have tested the use of differe…
We present an analysis of the radial profiles of a sample of 43 HI-flux selected spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) with resolved James Clerk Maxwell Telescope (JCMT) CO $J=3-2$ and/or Very Large Array (VLA) HI maps. Comparing the Virgo and non-Virgo populations, we confirm that the HI disks are truncated in the Virgo sample, even for these relatively HI-rich galaxies. On the other hand, the H$_{2}$ distribution is enhanced for Virgo galaxies near their centres, resulting in higher H$_{2}$ to HI ratios and steeper H$_{2}$ and total gas radial profiles. This is likely…
We use a sample of ~3000 galaxies from the MaNGA MPL-7 internal data release to study the alpha abundance distribution within low-redshift galaxies. We use the Lick index ratio Mgb/<Fe> as an alpha abundance indicator to study relationships between the alpha abundance distribution and galaxy properties such as effective stellar velocity dispersion within 0.3 effective radii (sigma_*), galaxy environment, and dark matter halo formation time (z_f). We find that (1) all galaxies show a tight correlation between Mgb/<Fe> and sigma_*; (2) `old' (H_beta < 3) low-sigma_* galaxies in high local densit…
The current properties of globular cluster systems (GCSs) are the result of the evolution experienced by their host galaxies, which shape the richness of the GCS as well as its spatial distribution, among other features. We carry out an analysis of the projected radial distribution of globular clusters for a sample of almost 30 early-type galaxies (ETGs) of intermediate and low luminosity, located in cluster environments (Virgo, Fornax and Coma). We also include in the study six ETGs, for which the parameters of their GCS radial profiles are publicly available. The final analysis is performed …
We examine how the cosmic environment affects the chemical evolution of galaxies in the Universe by comparing the N/O ratio of dwarf galaxies in voids with dwarf galaxies in more dense regions. Ratios of the forbidden [O III] and [S II] transitions provide estimates of a region's electron temperature and number density. We estimate the abundances of oxygen and nitrogen using these temperature and density estimates and the emission line fluxes [O II] 3727, [O III] 4959, 5007, and [N II] 6548, 6584 with the direct Te method. Using spectroscopic observations from the Sloan Digital Sky Survey Data…
Environmental Imprints on the Assembly of the Cool Gas around Bright Cluster Galaxies
Xiamen University（厦门大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；University of Chinese Academy of Sciences（中国科学院大学）；University of Science and Technology of China（中国科学技术大学）
