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Galaxy evolution depends on the environment in which galaxies are located. The various physical processes (ram-pressure stripping, tidal interactions, etc.) that are able to affect the gas content in galaxies have different efficiencies in different environments. In this work, we examine the gas (atomic HI and molecular H2) content of local galaxies inside and outside clusters, groups, and filaments as well as in isolation using a combination of observational and simulated data. We exploited a catalogue of galaxies in the Virgo cluster (including the surrounding filaments and groups) and compared the data against the predictions of the Galaxy Evolution and Assembly (GAEA) semi-analytic model, which has explicit prescriptions for partitioning the cold gas content in its atomic and molecular phases. We extracted from the model both a mock catalogue that mimics the observational biases and one not tailored to observations in order to study the impact of observational limits on the results and predict trends in regimes not covered by the current observations. The observations and simulated data show that galaxies within filaments exhibit intermediate cold gas content between galaxies in clusters and in isolation. The amount of HI is typically more sensitive to the environment than H2 and low-mass galaxies (log10[M⋆/M⊙]< 10) are typically more affected than their massive (log10[M⋆/M⊙]> 10) counterparts. Considering only model data, we identified two distinct populations among filament galaxies present in similar proportions: those simultaneously lying in groups and isolated galaxies. The former has properties more similar to cluster and group galaxies, and the latter is more similar to those of field galaxies. We therefore did not detect the strong effects of filaments themselves on the gas content of galaxies, and we ascribe the results to the presence of groups in filaments. [ABSTRACT FROM AUTHOR]

The assembly of galaxy clusters is understood to be a hierarchical process with a continuous accretion of galaxies over time, which increases the cluster size and mass. Late-type galaxies that fall into clusters can undergo ram-pressure stripping, forming extended gas tails within which star formation can happen. The number, location, and tail orientations of such galaxies provide clues about the galaxy infall process, the assembly of the cluster over time, and the consequences of infall for galaxy evolution. Here, we utilise the ∼0.5-degree diameter circular field of the Ultraviolet Imaging Telescope to image six galaxy clusters at z < 0.06 that are known to contain 'jellyfish' galaxies. We searched for stripping candidates in the ultraviolet images of these clusters, which revealed 54 candidates showing signs of unilateral extra-planar emission, due to ram-pressure stripping. Seven candidates had already been identified as likely stripping based on optical B-band imaging. We identified 47 new candidates through UV imaging. Spectroscopic redshift information is available for 39 of these candidate galaxies, of which 19 are associated with six clusters. The galaxies with spectroscopic redshifts that are not part of the clusters appear to be within structures at different redshifts identified as additional peaks in the redshift distribution of galaxies, indicating that they might be ram-pressure stripped or disturbed galaxies in other structures along the line of sight. We examine the orbital history of these galaxies based on their location in the position-velocity phase-space diagram and explore a possible connection to the orientation of the tail direction among cluster member candidates. There are limitations due to different integration times and imaging different regions with respect to the cluster centre. The tails of confirmed cluster member galaxies are found to be oriented away from the cluster centre. [ABSTRACT FROM AUTHOR]

Aims. In this work, we aim to characterize the stellar populations of star-forming regions detached from the stellar disks of galaxies undergoing ram-pressure stripping. Methods. Using images collected with the WFC3 camera on board of the Hubble Space Telescope, we detected stellar clumps in continuum-subtracted Hα and the ultraviolet (F275W filter); such clumps are often embedded in larger regions (star-forming complexes) detected in the optical (F606W filter). Our sample includes 347 Hα clumps, 851 F275W clumps, and 296 star-forming complexes. We modeled the photometry of these objects in five bands using BAGPIPES to obtain their stellar population parameters. Results. The median mass-weighted stellar ages are 27 Myr for Hα clumps and 39 Myr for F275W clumps and star-forming complexes, but the oldest stars in the complexes can be older than ∼300 Myr which indicates that star formation is sustained for long periods of time. Stellar masses vary from 103.5 to 107.1 M⊙, with star-forming complexes being more massive objects in the sample. Clumps and complexes found further away from the host galaxy are on average younger, less massive, and less obscured by dust. We interpret these trends as due to the effect of ram pressure in different phases of the interstellar medium. Hα clumps form a well-defined sequence in the stellar mass–SFR plane with a slope of 0.73. Some F275W clumps and star-forming complexes follow the same sequence while others stray away from it and passively age. The difference in mean stellar age between a complex and its youngest embedded clump scales with the distance between the clump and the center of the optical emission of the complex, with the most displaced clumps being hosted by the most elongated complexes. This is consistent with a fireball-like morphology, where star formation proceeds in a small portion of the complex while older stars are left behind producing a linear stellar population gradient. The stellar masses of star-forming complexes are consistent with the ones of globular clusters, but their stellar mass surface densities are lower by 2 dex, and their properties are more consistent with the population of dwarf galaxies in clusters. [ABSTRACT FROM AUTHOR]

Context. 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 > 2r200), are currently limited to the low redshift Universe. Deep and wide photometric data, better if combined with spectroscopic redshifts, are required to explore several scenarios on galaxy evolution at intermediate redshift. Aims. 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 the VLT Survey Telescope (VST-GAME) survey. The project is aimed at gathering deep (r < 24.4) and wide (approx. 20x20 Mpc2) observations at optical (u, ɡ, r, i, VST) wavelengths for six massive galaxy clusters at 0.2 < z < 0.6, complemented with near-infrared data (Y, J, Ks, VISTA, ESO public survey GCAV). The aim is to investigate galaxy evolution in a wide range of stellar masses and environmental conditions. This work describes the photometric analysis of the cluster and the definition of a density field, which will be a key ingredient for further studies on galaxy properties in the cluster outskirts. Methods. We extracted sources paying particular attention to recovering the faintest ones and simultaneously flagging point sources and sources with photometry affected by artifacts in the images. We combined all the extractions in a multiband catalog that is used to derive photometric redshifts through spectral energy distribution (SED) fitting. We then defined cluster memberships up to 5r200 from the cluster core and measure the density field, comparing galaxy properties in different environments. Results. We find that the ɡ – r colors show bimodal behaviors 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 three overdense regions in the cluster outskirts at r ~ 5r200. Galaxies in these structures have mean densities and luminosities similar to those of the cluster core. The color of galaxies suggests the presence of evolved galaxy populations, an insight into preprocessing phenomena over these substructures. We release the multiband catalog, down to the completeness limit of r < 24.4 mag. [ABSTRACT FROM AUTHOR]

Exploiting a sample of galaxies drawn from the XXL-North multiwavelength survey, we present an analysis of the stellar population properties of galaxies at 0.1 ≤ z ≤ 0.5, by studying galaxy fractions and the star formation rate (SFR)–stellar mass (M⋆) relation. Furthermore, we exploit and compare two parametrisations of environment. When adopting a definition of "global" environment, we consider separately cluster virial (r ≤ 1r200) and outer (1r200 <  r ≤ 3r200) members and field galaxies. We also distinguish between galaxies that belong or do not belong to superclusters, but never find systematic differences between the two subgroups. When considering the "local" environment, we take into account the projected number density of galaxies in a fixed aperture of 1 Mpc in the sky. We find that regardless of the environmental definition adopted, the fraction of blue or star-forming galaxies is the highest in the field or least dense regions and the lowest in the virial regions of clusters or highest densities. Furthermore, the fraction of star-forming galaxies is higher than the fraction of blue galaxies, regardless of the environment. This result is particularly evident in the virial cluster regions, most likely reflecting the different star formation histories of galaxies in different environments. Also the overall SFR–M⋆ relation does not seem to depend on the parametrisation adopted. Nonetheless, the two definitions of environment lead to different results as far as the fraction of galaxies in transition between the star-forming main sequence and the quenched regime is concerned. In fact, using the local environment the fraction of galaxies below the main sequence is similar at low and high densities, whereas in clusters (and especially within the virial radii) a population with reduced SFR with respect to the field is observed. Our results show that the two parametrisations adopted to describe the environment have different physical meanings, i.e. are intrinsically related to different physical processes acting on galaxy populations and are able to probe different physical scales. [ABSTRACT FROM AUTHOR]

Aims. Using V band photometry of the WINGS survey, we derive galaxy luminosity functions (LF) in nearby clusters. This sample is complete down to MV = -15.15, and it is homogeneous, thus facilitating the study of an unbiased sample of clusters with different characteristics. Methods. We constructed the photometric LF for 72 out of the original 76 WINGS clusters, excluding only those without a velocity dispersion estimate. For each cluster we obtained the LF for galaxies in a region of radius = 0.5 x r200, and fitted them with single and double Schechter's functions. We also derive the composite LF for the entire sample, and those pertaining to different morphological classes. Finally, we derive the spectroscopic cumulative LF for 2009 galaxies that are cluster members. Results. The double Schechter fit parameters are correlated neither with the cluster velocity dispersion nor with the X-ray luminosity. Our median values of the Schechter's fit slope are, on average, in agreement with measurements of nearby clusters, but are less steep that those derived from large surveys, such as the SDSS. Early-type galaxies out number late-types at all magnitudes, but both early and late types contribute equally to the faint end of the LF. Finally, the spectroscopic LF is in excellent agreement with the one derived for A2199, A85 and Virgo, and with the photometric LF at the bright magnitudes (where both are available). Conclusions. There is a large spread in the LF of different clusters, however, this spread is not caused by correlation of the LF shape with cluster characteristics such as X-ray luminosity or velocity dispersions. The faint end is flatter than previously derived (αf = -1.7), which is at odds with that predicted from numerical simulations. [ABSTRACT FROM AUTHOR]

Context. Wide-field observations targeting galaxy clusters at low redshift are complementary to field surveys and provide the local benchmark for detailed studies of the most massive haloes in the local Universe. The Wide-field Nearby Galaxy-cluster Survey (WINGS) is a wide-field multi-wavelength survey of X-ray selected clusters at z = 0.04-0.07. The original 34' x 34' WINGS field of view has now been extended to cover a 1 deg² field with both photometry and spectroscopy. Aims. We present the Johnson B- and V-band OmegaCAM at the VST observations of 46 WINGS clusters together with the data reduction, data quality, and Sextractor photometric catalogues. Methods. The data reduction was carried out with a modified version of the ESO-MVM (also known as ALAMBIC) reduction package, adding a cross-talk correction, the gain harmonisation, and a control procedure for problematic CCDs. The stray-light component was corrected for by employing our own observations of populated stellar fields. Results. With a median seeing of 1" in both bands, our 25-min exposures in each band typically reach the 50% completeness level at V = 23.1 mag. The quality of the astrometric and photometric accuracy has been verified by comparison with the 2MASS and SDSS astrometry, and SDSS and previous WINGS imaging. Star-to-galaxy separation and sky-subtraction procedure were tested comparing them with previous WINGS data. Conclusions. The Sextractor photometric catalogues are publicly available at the CDS and will be included in the next release of the WINGS database on the Virtual Observatory together with the OmegaCAM reduced images. These data form the basis for a large ongoing spectroscopic campaign with AAOmega at the AAT and are being employed for a variety of studies. [ABSTRACT FROM AUTHOR]

Context. To effectively investigate galaxy formation and evolution, it is of paramount importance to exploit homogeneous data for large samples of galaxies in different environments. Aims. The WIde-field Nearby Galaxy-cluster Survey (WINGS) project aim is to evaluate physical properties of galaxies in a complete sample of low redshift clusters to be used as reference sample for evolutionary studies. The WINGS survey is still ongoing and the original dataset will be enlarged with new observations. This paper presents the entire collection of WINGS measurements obtained so far. Methods. We decided to make use of the Virtual Observatory (VO) tools to share the WINGS database (that will be updated regularly) with the community. In the database each object has one unique identification (WINGSID). Each subset of estimated properties is accessible using a cone search (including wide-field images). Results. We provide the scientific community with the entire set of wide-field images. Furthermore, the published database contains photometry of 759 024 objects and surface brightness analysis for 42 275 and 41 463 galaxies in the V and B band, respectively. The completeness depends on the image quality, and on the cluster redshift, reaching on average 90% at V ⩽ 21.7. Near-infrared photometric catalogs for 26 (in K) and 19 (in J) clusters are part of the database and the number of sources is 962 344 in K and 628 813 in J. Here again the completeness depends on the data quality, but it is on average higher than 90% for J ⩽ 20.5 and K ⩽ 19.4. The IR subsample with a Sersic fit comprises 71 687 objects. A morphological classification is available for 39 923 galaxies. We publish spectroscopic data, including 6132 redshifts, 5299 star formation histories, and 4381 equivalent widths. Finally, a calculation of local density is presented and implemented in the VO catalogs for 66 164 galaxies. The latter is presented here for the first time. [ABSTRACT FROM AUTHOR]

We present an analysis of the galaxy stellar mass function in different environments at intermediate redshift (0.3 ⩽ z ⩽ 0.8) for two mass-limited galaxy samples. We use the IMACS Cluster Building Survey (ICBS; M∙ ⩾ 1010.5 M°) to study cluster, group and field galaxies at z = 0.3-0.45, and the ESO Distant Cluster Survey (EDisCS; M∙ ⩾ 1010.2 M°) to investigate cluster and group galaxies at z = 0.4-0.8. Our analysis thus includes galaxies with masses reaching just below that of the Milky Way. Excluding the brightest cluster galaxies, we show that the shape of the mass distribution does not seem to depend on global environment, Our two main results are: (1) Galaxies in the virialised regions of clusters, in groups, and in the field follow similar mass distributions. (2) Comparing the ICBS and EDisCS mass functions to mass functions in the local universe, we detect evolution from z ∼ 0.4-0.6 to z ∼ 0.07 in the sense that the population of low-mass galaxies has grown with time with respect to the population of massive galaxies. This evolution is independent of environment, i.e., the same for clusters and the field. Furthermore, considering only cluster galaxies, we find that no differences can be detected in their mass functions either within the virialised regions, or when we compare galaxies inside and outside the virial radius. Finally, we find that red and blue galaxies have different mass functions. However, the shapes of the mass functions of blue and red galaxies do not seem to depend on their environment (clusters groups and the field). [ABSTRACT FROM AUTHOR]

We present new spectroscopic observations in a field containing the highest redshift cluster of the ESO Distant Cluster Survey (EDisCS). We measure galaxy redshifts and determine the velocity dispersions of the galaxy structures located in this field. Together with the main cluster Cl 1103.7-1245 (z = 0.9580; σclus = 522 ± 111 km s-1) we find a secondary structure at z = 0.9830, Cl 1103.7-1245c. We then characterize the galaxy properties in both systems, and find that they contain very different galaxy populations. The cluster Cl 1103.7-1245 hosts a mixture of passive elliptical galaxies and star-forming spirals and irregulars. In the secondary structure Cl 1103.7-1245c all galaxies are lower-mass star-forming irregulars and peculiars. In addition, we compare the galaxy populations in the Cl 1103.7-1245 z = 0.9580 cluster with those in lower redshift EDisCS clusters with similar velocity dispersions. We find that the properties of the galaxies in Cl 1103.7-1245 follow the evolutionary trends found at lower redshifts: the number of cluster members increases with time in line with the expected growth in cluster mass, and the fraction of passive early-type galaxies increases with time while star-forming late types become less dominant. Finally, we find that the mean stellar masses are similar in all clusters, suggesting that massive cluster galaxies were already present at z ∼ 1. [ABSTRACT FROM AUTHOR]