arXiv subjects

Valeria Coenda

Publications and source records attributed to Valeria Coenda.

26 records · Page 2Linked to original sources

arXiv2015

Galaxies infalling into groups: filaments vs. isotropic infall

We perform a comparative analysis of the properties of galaxies infalling into groups classifying them accordingly to whether they are: falling along filamentary structures; or they are falling isotropically. For this purpose, we identify filamentary structures connecting massive groups of galaxies in the SDSS. We perform a comparative analysis of some properties of galaxies in filaments, in the isotropic infall region, in the field, and in groups. We study the luminosity functions (LF) and the dependence of the specific star formation rate (SSFR) on stellar mass, galaxy type, and projected distance to the groups that define the filaments. We find that the LF of galaxies in filaments and in the isotropic infalling region are basically indistinguishable between them, with the possible exception of late-type galaxies. On the other hard, regardless of galaxy type, their LFs are clearly different from that of field or group galaxies. Both of them have characteristic absolute magnitudes and faint end slopes in between the field and group values. More significant differences between galaxies in filaments and in the isotropic infall region are observed when we analyse the SSFR. We find that galaxies in filaments have a systematically higher fraction of galaxies with low SSFR as a function of both, stellar mass and distance to the groups, indicating a stronger quenching of the star formation in the filaments compared to both, the isotropic infalling region, and the field. Our results suggest that some physical mechanisms that determine the differences observed between field galaxies and galaxies in systems, affect galaxies even when they are not yet within the systems.

astro-ph.GA↗

arXiv2015

Tidal stripping of globular clusters in a simulated galaxy cluster

Using a cosmological N-body numerical simulation of the formation of a galaxy cluster- sized halo, we analyze the temporal evolution of its globular cluster population. We follow the dynamical evolution of 38 galactic dark matter halos orbiting in a galaxy cluster that at redshift z=0 has a virial mass of 1.71 * 10 ^14 Msol h^-1. In order to mimic both "blue" and "red" populations of globular clusters, for each galactic halo we select two different sets of particles at high redshift (z ~ 1), constrained by the condition that, at redshift z=0, their average radial density profiles are similar to the observed profiles. As expected, the general galaxy cluster tidal field removes a significant fraction of the globular cluster populations to feed the intracluster population. On average, halos lost approximately 16% and 29% of their initial red and blue globular cluster populations, respectively. Our results suggest that these fractions strongly depend on the orbital trajectory of the galactic halo, specifically on the number of orbits and on the minimum pericentric distance to the galaxy cluster center that the halo has had. At a given time, these fractions also depend on the current clustercentric distance, just as observations show that the specific frequencyof globular clusters S_N depends on their clustercentric distance.

astro-ph.GA↗

arXiv2014

Comparing galaxy populations in compact and loose groups of galaxies III. Effects of environment on star formation

This paper is part of a series in which we perform a systematic comparison of the galaxy properties inhabiting compact groups, loose groups and the field. In this paper we focus our study to the age and the star formation in galaxies. For galaxies in selected samples of compact groups, loose groups and field, we compare the distributions of the following parameters: D$_n(4000)$ as an age indicator, and the specific star formation rate as indicator of ongoing star formation. We analyse the dependence of these parameters on galaxy type, stellar mass and, for group galaxies, their dependence on the dynamic state of the system. We also analyse the fraction of old, and of high star forming galaxies as a function of galaxy stellar mass in the environments we probe. Galaxies in compact groups have, on average, older stellar populations than their loose group or field counterparts. Early-type 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. 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.

astro-ph.GA↗

arXiv2013

Comparing galaxy populations in compact and loose groups of galaxies II: brightest group galaxies

The properties of the brightest galaxies (BCGs) are studied in both compact and loose groups of galaxies in order to better understand the physical mechanisms influencing galaxy evolution in different environments. Samples of BCGs are selected in the compact groups identified by McConnachie et al. (2009), and in loose groups taken from Zandivarez & Martínez (2011). The following physical properties of the BCGs in compact groups and in subsamples of loose groups are compared, defined by their mass and total luminosity. The fraction of BCGs classified as red and/or early-type as a function of galaxy luminosity are studied. The fraction of the group's total luminosity contained in the BCG and the difference in luminosity between the BCG and the second-ranked galaxy, are also analysed. Some properties of BCGs in compact and loose groups are comparable. However, BCGs in compact groups are systematically more concentrated and have larger surface brightness than their counterparts in both, high- and low-mass loose groups. The fractions of red and early-type BCGs in compact groups are consistent with those of high-mass loose groups. Comparing BCGs in subsamples of compact and loose groups selected for their similar luminosities, BCGs in compact groups are found to be, on average, brighter, more massive, larger, redder and more frequently classified as elliptical. In compact groups, the BCG contains a larger fraction of the system's total luminosity and differs more in absolute magnitude from the second-ranked galaxy. BCGs in compact and loose groups are found to be different. Some mechanisms responsible for transforming late-type galaxies into early types, such as mergers, may be more effective within compact groups due to their high densities and small velocity dispersion, which would lead their BCGs along somewhat different evolutionary paths.

astro-ph.CO↗

arXiv2012

Comparing galaxy populations in compact and loose groups of galaxies

We perform a comparison of the properties of galaxies in compact groups, loose groups and in the field to deepen our understanding of the physical mechanisms acting upon galaxy evolution in different environments. We select samples of galaxies in compact groups identified by McConnachie et al., loose groups identified by Zandivarez and Martinez, and field galaxies from the Sloan Digital Sky Survey. We compare properties of the galaxy populations in these different environments: absolute magnitude, colour, size, surface brightness, stellar mass and concentration. We also study the fraction of red and early type galaxies, the luminosity function, the colour-luminosity and luminosity-size relations. The population of galaxies in compact groups differ from that of loose groups and the field. The fraction of read and early type galaxies is higher in compact groups. On average, galaxies in compact groups are systematically smaller, more concentrated and have higher surface brightness than galaxies in the field and in loose groups. For fixed absolute magnitude, or fixed surface brightness, galaxies in compact groups are smaller. The physical mechanisms that transform galaxies into earlier types could be more effective within compact groups given the high densities and low velocity dispersion that characterise that particular environment, this could explain the large fraction of red and early type galaxies we found in compact groups. Galaxies inhabiting compact groups have undergone a major transformation compared to galaxies that inhabit loose groups.

astro-ph.CO↗

arXiv2009

The environmental dependence of the red galaxy sequence

The dependence of the sequence of red galaxies (RS) with the environment is investigated using field, group, and cluster galaxies drawn from the SDSS. Our work focuses in studying the mean colour ($μ_R$) and the scatter ($σ_R$) of the RS as a function absolute magnitude in different environments characterised either by the mass of the system in which the galaxies are located or by the distance to the system's centre. The same analysis is carried out using red early type galaxies. For a given luminosity, $μ_R$ of field galaxies is bluer and $σ_R$ is larger than their group and cluster counterparts irrespective of mass and position within the systems. Among systems of galaxies, high mass groups and clusters have the reddest $μ_R$ and the smallest $σ_R$. These differences almost disappear when red early type galaxies alone are considered. Galaxies in the core and in the outskirts of groups have similar $μ_R$, whereas galaxies in clusters show a strong dependence on cluster centric distance. Red early type galaxies in the outskirts of clusters have $σ_R$ values as large as field galaxies', while galaxies in the inner regions of clusters have lower values. We find that bright red early type galaxies have reached nearly the same evolutionary stage in all environments. Our results suggest that the cluster environment is not necessary to populate the RS. We propose a scenario in which the RS in massive systems is populated by two different star formation history galaxies: red early type galaxies that formed the bulk of their stars during the early stages of massive halo assembly, and red galaxies that passed most of their lives inhabiting poor groups or the field and fell into massive systems at lower redshifts.

astro-ph.CO↗

arXiv2009

Tidal Stripping of Globular Clusters in the Virgo Cluster

With the aim of finding evidence of tidal stripping of globular clusters (GCs) we analysed a sample of 13 elliptical galaxies taken from the ACS Virgo Cluster Survey (VCS). These galaxies belong to the main concentration of the Virgo cluster (VC) and present absolute magnitudes $-18.5<M_z<-22.5$. We used the public GC catalog of Jordán et al. (2008) and separated the GC population into metal poor (blue) and metal rich (red) according to their integrated colors. The galaxy properties were taken from \citet{Peng:2008}. We found that: 1) The specific frequencies ($S_N$) of total and blue GC populations increase as a function of the projected galaxy distances $r_p$ to M87. A similar result is observed when 3-dimensional distances $r_{3D}$ are used. The same behaviours are found if the analysis are made using the number of GCs per $10^9\Msun$ ($T$). The correlations with the clustocentric distance of the host galaxy are interpreted as evidence of GCs stripping due to tidal forces. 2) No correlation is found between the slope of GC density profiles of host galaxies and the galaxy distance to M87 (Virgo central galaxy). 3) We also computed the local density of GCs ($ρ_{out}$) located further than $6.2 \kpc$ from the galaxy center for nine galaxies of our sample. We find that the GC population around most of these galaxies is mainly composed of blue GCs. Our results suggest that the number and the fraction of blue and red GCs observed in elliptical galaxies located near the centers of massive clusters, could be significantly different from the underlying GC population. These differences could be explained by tidal stripping effects that occur as galaxies approach the centers of clusters.

astro-ph.CO↗

arXiv2008

On the relationship between environment and galaxy properties in clusters of galaxies

We study the correlation between different properties of bright (L>L*) 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 M~10^{14}M_sun. On the other hand, galaxy properties correlate with cluster-centric distance. The property most affected by the cluster-centric distance is g-r colour, closely followed by the u-r 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 Martinez & Muriel for groups of galaxies and Blanton at al. for the local density of field galaxies.

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