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We study the population of backsplash galaxies at z  = 0 in the outskirts of massive, isolated clusters of galaxies taken from the mdpl 2- sag semi-analytical catalogue. We consider four types of backsplash galaxies according to whether they are forming stars or passive at three stages in their lifetimes: before entering the cluster, during their first incursion through the cluster, and after they exit the cluster. We analyse several geometric, dynamic, and astrophysical aspects of the four types at the three stages. Galaxies that form stars at all stages account for the majority of the backsplash population (58 per cent) and have stellar masses typically below |$M_\star \sim 3\times 10^{10} \ h^{-1}\, {\rm {M_\odot }}$| that avoid the innermost cluster's regions and are only mildly affected by it. In a similar mass range, galaxies that become passive after exiting the cluster (26 per cent) follow orbits characterized by small pericentric distance and a strong deflection by the cluster potential well while suffering a strong loss of both dark matter and gas content. Only a small fraction of our sample (4 per cent) becomes passive while orbiting inside the cluster. These galaxies have experienced heavy pre-processing and the cluster's tidal stripping and ram pressure provide the final blow to their star formation. Finally, galaxies that are passive before entering the cluster for the first time (12 per cent) are typically massive and are not affected significantly by the cluster. Using the bulge/total mass ratio as a proxy for morphology, we find that a single incursion through a cluster does not result in significant morphological changes in all four types. [ABSTRACT FROM AUTHOR]

We use the roger code by de los Rios et al. to classify galaxies around a sample of X-ray clusters into five classes according to their positions in the projected phase space diagram: cluster galaxies, backsplash galaxies, recent infallers, infalling galaxies, and interlopers. To understand the effects of the cluster environment to the evolution of galaxies, we compare across the five classes: stellar mass, specific star formation rate, size, and morphology. Following the guidelines of Coenda et al. a separate analysis is carried out for red and blue galaxies. For red galaxies, cluster galaxies differ from the other classes, having a suppressed specific star formation rate, smaller sizes, and are more likely to be classified as ellipticals. Differences are smaller between the other classes, however backsplash galaxies have significantly lower specific star formation rates than early or recent infalling galaxies. For blue galaxies, we find evidence that recent infallers are smaller than infalling galaxies and interlopers, while the latter two are comparable in size. Our results provide evidence that, after a single passage, the cluster environment can diminish a galaxy's star formation, modify its morphology, and can also reduce in size blue galaxies. We find evidence that quenching occurs faster than morphological transformation from spirals to ellipticals for all classes. While quenching is evidently enhanced as soon as galaxies get into clusters, significant morphological transformations require galaxies to experience the action of the physical mechanisms of the cluster for longer time-scales. [ABSTRACT FROM AUTHOR]

We connect galaxy properties with their orbital classification by analysing a sample of galaxies with stellar mass M ⋆ ≥ 108.5 h −1M⊙ residing in and around massive and isolated galaxy clusters with mass M 200 > 1015 h −1M⊙ at redshift z  = 0. The galaxy population is generated by applying the semi-analytic model of galaxy formation sag  on the cosmological simulation MultiDark Planck 2. We classify galaxies considering their real orbits (3D) and their projected phase-space position using the roger   code (2D). We define five categories: cluster galaxies, galaxies that have recently fallen into a cluster, backsplash galaxies, infalling galaxies, and interloper galaxies. For each class, we analyse the 0.1(g − r) colour, the specific star formation rate (sSFR), and the stellar age, as a function of the stellar mass. For the 3D classes, we find that cluster galaxies have the lowest sSFR, and are the reddest and the oldest, as expected from environmental effects. Backsplash galaxies have properties intermediate between the cluster and recent infaller galaxies. For each 2D class, we find an important contamination by other classes. We find it necessary to separate the galaxy populations in red and blue to perform a more realistic analysis of the 2D data. For the red population, the 2D results are in good agreement with the 3D predictions. Nevertheless, when the blue population is considered, the 2D analysis only provides reliable results for recent infallers, infalling galaxies and interloper galaxies. [ABSTRACT FROM AUTHOR]

We present the ROGER (Reconstructing Orbits of Galaxies in Extreme Regions) code, which uses three different machine learning techniques to classify galaxies in, and around, clusters, according to their projected phase-space position. We use a sample of 34 massive, M 200 > 1015 h −1 M ⊙, galaxy clusters in the MultiDark Planck 2 (MDLP2) simulation at redshift zero. We select all galaxies with stellar mass M ⋆ ≥ 108.5 h −1 M ⊙, as computed by the semi-analytic model of galaxy formation SAG, that are located in, and in the vicinity of, these clusters and classify them according to their orbits. We train ROGER to retrieve the original classification of the galaxies from their projected phase-space positions. For each galaxy, ROGER gives as output the probability of being a cluster galaxy, a galaxy that has recently fallen into a cluster, a backsplash galaxy, an infalling galaxy, or an interloper. We discuss the performance of the machine learning methods and potential uses of our code. Among the different methods explored, we find the K-Nearest Neighbours algorithm achieves the best performance. [ABSTRACT FROM AUTHOR]

Aims. We explore the effects of environment in the evolution of late-type galaxies by studying the radial profiles of light- and mass-weighted metallicities of galaxies in two discrete environments: field and groups. Methods. We used a sample of 167 late-type galaxies with stellar masses of 9 ≤ log(M⋆/M⊙) ≤ 12 drawn from the Calar Alto Legacy Integral Field Area (CALIFA) survey. Firstly, we obtained light- and mass-weighted stellar metallicity profiles and stellar mass density profiles of these galaxies using publicly available data. We then classified them according to their environment into field and group galaxies. Finally, we studied the metallicity of galaxies in these two environments, including a comparison of the metallicity as a function of radius, at a characteristic scale, and as a function of stellar mass surface density. As metallicity depends on galaxy mass, we took special care throughout the study to compare, in all cases, subsamples of galaxies in groups and in the field that have similar masses. Results. We find significant differences between group and field late-type galaxies in terms of their metallicity: group galaxies are systematically higher in metallicity than their field counterparts. We find that field galaxies, in general, have metallicity profiles that show a negative gradient in their inner regions and a shallower profile at larger radii. This is in contrast to the metallicity profiles of galaxies in groups, which tend to be flat in the inner regions and to have a negative gradient in the outer parts. Regarding the metallicity at the characteristic radius of the luminosity profiles, we consistently find that it is higher for group galaxies irrespective of galaxy mass. At fixed local stellar surface mass density, group galaxies are again higher in metallicity, also the dependence of metallicity on surface density is less important for group galaxies. Conclusions. The evidence of a clear difference in metallicity between group and field galaxies as a function of mass, spatial scale, and local stellar mass density is indicative of the different evolutionary paths followed by galaxies in groups and in the field. We discuss some possible implications of the observed differences. [ABSTRACT FROM AUTHOR]

We study the effects of the environment on galaxy quenching in the outskirts of clusters at 0.04 < z < 0.08. We use a subsample of 14 WINGS and OmegaWINGS clusters that are linked to other groups/clusters by filaments and study separately galaxies located in two regions in the outskirts of these clusters according to whether they are located towards the filaments' directions or not. We also use samples of galaxies in clusters and field as a comparison. Filamentary structures linking galaxy groups/clusters were identified over the Six Degree Field Galaxy Redshift Survey Data Release 3. We find a fraction of passive galaxies in the outskirts of clusters intermediate between that of the clusters and the field's. We find evidence of a more effective quenching in the direction of the filaments. We also analyse the abundance of post-starburst (PS) galaxies in the outskirts of clusters focusing our study on two extreme sets of galaxies according to their phase-space position: backsplash and true infallers. We find that up to |$\sim 70{{\ \rm per\ cent}}$| of PS galaxies in the direction of filaments are likely backsplash, while this number drops to |$\sim 40{{\ \rm per\ cent}}$| in the isotropic infall region. The presence of this small fraction of galaxies in filaments that are falling into clusters for the first time and have been recently quenched, supports a scenario in which a significant number of filament galaxies have been quenched long time ago. [ABSTRACT FROM AUTHOR]

We study the quenching of galaxies in different environments and its evolution in the redshift range 0.43 ≤ |$z$| ≤ 0.89. For this purpose, we identify galaxies inhabiting filaments, the isotropic infall region of groups, the field, and groups in the VIMOS Public Extragalactic Redshift Survey (VIPERS). We classify galaxies as quenched (passive), through their NUV − r versus r − K colours. We study the fraction of quenched galaxies (Fr) as a function of stellar mass and environment at two redshift intervals. Our results confirm that stellar mass is the dominant factor determining galaxy quenching over the full redshift range explored. We find compelling evidence of evolution in the quenching of intermediate mass galaxies (9.3 ≤ log (M ⋆/ M ⊙) ≤ 10.5) for all environments. For this mass range, Fr is largest for galaxies in groups and smallest for galaxies in the field, while galaxies in filaments and in the isotropic infall regions appear to have intermediate values with the exception of the high redshift bin, where the latter show similar fraction of quenched galaxies as in the field. Galaxies in filaments are systematically more quenched than their counterparts infalling from other directions, in agreement to similar results found at low redshift. The least massive galaxies in our samples do not show evidence of internal or environmental quenching. [ABSTRACT FROM AUTHOR]

Aims. This paper is part of a series in which we systematically compare the properties of galaxies in compact groups, loose groups, and the field. In this paper we focus our study on the age and star formation in galaxies. Methods. For galaxies in selected samples of compact groups, loose groups, and field galaxies, we compare the distributions of Dn(4000) as an age indicator and the specific star formation rate as an indicator of on-going star formation. We analyse the dependence of these parameters on galaxy type and stellar mass and, for group galaxies, their dependence on the dynamic state of the system. We study the relative fraction of galaxies dominated by old stellar populations as a function of galaxy stellar mass. We perform a similar analysis for galaxies that have high specific star formation rates. Results. Galaxies in compact groups have, on average, older stellar populations than their loose-group or field counterparts. Earlytype galaxies in compact groups formed their stars and depleted their gas content more rapidly than in the other environments. We have found evidence of two populations of late-type galaxies in dynamically old compact groups: one with normal specific star formation rates and another with markedly reduced star formation. Conclusions. Processes that transform galaxies from star forming to quiescent act upon galaxies faster and more effectively in compact groups. The unique characteristics of compact groups make them an extreme environment for galaxies, where the transition to quiescence occurs rapidly. [ABSTRACT FROM AUTHOR]

ABSTRACT We perform an exhaustive analysis of the luminosities of galaxies in groups identified in the Sloan Digital Sky Survey (SDSS) Data Release 7. Our main purpose is to perform a detailed study of the Schechter luminosity function parameters: the characteristic absolute magnitude and the faint-end slope, as a function of group virial mass in order to quantify their dependence on environment. We analyse the trends of the Schechter parameters as a function of group mass for different photometric bands, galaxy populations, galaxy positions within the groups and the group surrounding large-scale density. We find that the characteristic magnitude brightens and the faint-end slope becomes steeper as a function of mass in all SDSS photometric bands, in agreement with previous results. From the analysis of different galaxy populations, we observe that different methods to split galaxy populations, based on the concentration index or the colour-magnitude diagram, produce quite different behaviours in the luminosity trends, mainly for the faint-end slope. These discrepancies and the trends with mass mentioned above are explained when analysing the luminosity function of galaxies classified simultaneously according to their concentrations and colours. We find that only the red spheroids have a luminosity function that strongly depends on group mass. Late-type galaxies, whether blue or red, have luminosity functions that do not depend on group mass. The intrinsic change in the luminosity function of spheroids and the varying number contributions of the different types explain the overall trend of the luminosity function with group mass. On the other hand, dividing the galaxy members in the inner and outer regions of the groups do not introduce a significant difference in the Schechter parameter trends, except for the characteristic absolute magnitude in the high group virial mass range () which is an indication of luminosity segregation in massive groups. Finally, we also analyse the possible influence of the large-scale surrounding environment on the luminosity function of group galaxies. We find that galaxies inhabiting groups at low-density regions experience more pronounced variations on the Schechter parameters as a function of groups mass, while galaxies in groups at high-density regions show an almost constant behaviour. We discuss the possible implications of our findings in the galaxy evolution scenario. [ABSTRACT FROM AUTHOR]

We study the correlation between different properties of bright galaxies in clusters and the environment in the Sloan Digital Sky Survey (SDSS). Samples of clusters of galaxies used in this paper are those selected by Coenda & Muriel that are drawn from the Popesso et al. and Koester et al. samples. Galaxies in these clusters have been identified in the main Galaxy sample of the Fifth Data Release (DR5) of SDSS. We analyse which galaxy properties correlate best with either cluster mass or cluster-centric distance using the technique by Blanton et al. We find that galaxy properties do not clearly depend on cluster mass for clusters more massive than . On the other hand, galaxy properties correlate with cluster-centric distance. The property most affected by the cluster-centric distance is colour, closely followed by the colour. These results are irrespective of the cluster selection criteria. The two samples of clusters were identified based on the X-ray emission and the galaxy colours, respectively. Moreover, the parameter that best predicts environment (i.e. cluster-centric distance) is the same found by Martínez & Muriel for groups of galaxies and Blanton et al. for the local density of field galaxies. [ABSTRACT FROM AUTHOR]

We analyse colour distributions for several samples of galaxies in groups drawn from the fourth data release of the Sloan Digital Sky Survey. For all luminosity ranges and environments considered, the colour distributions are well described by the sum of two Gaussian functions. We find that the fraction of galaxies in the red sequence is an increasing function of group virial mass. We also study the evolution of the galaxy colour distributions at low redshift, in the field and in groups for galaxies brighter than , finding significant evidence of recent evolution in the population of galaxies in groups. The fraction of red galaxies monotonically increases with decreasing redshift, this effect implies a much stronger evolution of galaxies in groups than in the field. [ABSTRACT FROM AUTHOR]