89 research outputs found
Galaxy properties in clusters. II. Backsplash Galaxies
We explore the properties of galaxies on the outskirts of clusters and their
dependence on recent dynamical history in order to understand the real impact
that the cluster core has on the evolution of galaxies. We analyse the
properties of more than 1000 galaxies brighter than =-19.6 on the
outskirts of 90 clusters () in the redshift range .
Using the line of sight velocity, we selected high and low velocity subsamples.
Theoretical predictions indicate that a significant fraction of the first
subsample should be backsplash galaxies, that is, objects that have already
orbited near the cluster centre. A significant proportion of the sample of high
relative velocity HV galaxies seems to be composed of infalling objects. Our
results suggest that, at fixed stellar mass, late type galaxies in the low
velocity LV sample are systematically older, redder and have formed fewer stars
during the last 3 Gyrs than galaxies in the HV sample. This result is
consistent with models that assume that the central regions of clusters are
effective in quenching the star formation by means of processes such as ram
pressure stripping or strangulation. At fixed stellar mass, LV galaxies show
some evidence of having higher surface brightness and smaller size than HV
galaxies. These results are consistent with the scenario where galaxies that
have orbited the central regions of clusters are more likely to suffer tidal
effects, producing loss of mass as well as a redistribution of matter towards
more compact configurations. Finally, we found a higher fraction of ET galaxies
in the LV sample, supporting the idea that the central region of clusters of
galaxies may contribute to the transformation of morphological types towards
earlier types.Comment: Accepted for publication in Astronomy & Astrophysics (A&A
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 & Mart\'inez (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.Comment: Accepted for publication in Astronomy & Astrophysics (A&A
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.Comment: 11 pages, 8 figures. Accepted for publication in Ap
Comparing galaxy populations in compact and loose groups of galaxies III. Effects of environment on star formation
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. 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. 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.Fil: Coenda, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Muriel, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Martinez Atencio, Hector Julian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentin
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.Comment: Accepted in MNRAS, 10 pages, 8 figure
Backsplash Galaxies
Abstract. We explore the properties of galaxies on the outskirts of clusters and their dependence on recent dynamical history in order to understand the real impact that the cluster core has on the evolution of galaxies.publishedVersionFil: Muriel, Hernán. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Muriel, Hernán. Conicet, Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Argentina.Fil: Coenda, Valeria. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Coenda, Valeria. Conicet, Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Argentina.Astronomía (incluye Astrofísica y Ciencias del Espacio
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