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

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

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

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

Cúmulos de galaxias : propiedades de galaxias y subsistemas

Tesis (Doctor en Astronomía)--Unviersidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2008.En la presente tesis se llevó a cabo un estudio estadístico sobre la dependencia de las propiedades de las galaxias brillantes y sus subsistemas como función de los parámetros globales de los cúmulos masivos de galaxias, con el fin de profundizar en el entendiemiento de los procesos físicos que intervienen en la formación y evolución de las galaxias. Para ello hemos utilizado diferentes catálogos reales y sintéticos de cúmulos de galaxias, con muestras homogéneas de galaxias

Comparing galaxy populations in compact and loose groups of galaxies

Abstract.We compare the properties of galaxies in compact groups, loose groups, and the eld to deepen our understanding of the physical mechanisms acting upon galaxy evolution in dierent environments. This contribution is detailed in Coenda et al. (2012) and Martínez et al. (2013).Fil: Martínez, Héctor Julián Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Martínez, Héctor Julián Conicet. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Coenda, Valeria Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil:Coenda, Valeria Conicet. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Muriel, Hernán Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Muriel, Hernán Conicet. Instituto de Astronomía Teórica y Experimental; Argentina.http://adsabs.harvard.edu/abs/2014RMxAC..44...81MpublishedVersionAstronomía (incluye Astrofísica y Ciencias del Espacio

Green valley galaxies as a transition population in different environments

We present a comparative analysis of the properties of passive, star-forming and transition (green valley) galaxies in four discrete environments: field, groups, the outskirts and the core of X-ray clusters. We construct samples of galaxies from the Sloan Digital Sky Survey in these environments so that they are bound to have similar redshift distributions. The classification of galaxies into the three sequences is based on theUV-optical colourNUV-r. We study a number of galaxy properties: stellar mass, morphology, specific star formation rate and the history of star formation. The analysis of green valley (GV) galaxies reveals that the physical mechanisms responsible for external quenching become more efficient moving from the field to denser environments. We confirm previous findings thatGVgalaxies have intermediate morphologies; moreover, we find that this appears to be independent of the environment. Regarding the stellar mass of GV galaxies, we find that they tend to be more massive in the field than in denser environments. On average, GV galaxies account for ~20 per cent of all galaxies in groups and X-ray clusters. We find evidence that the field environment is inefficient in transforming lowmass galaxies. GV galaxies have average star formation histories intermediate between passive and star-forming galaxies, and have a clear and consistent dependence on the environment: both, the quenching time and the amplitude of the star formation rate, decrease towards higher density environments.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: 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; 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; Argentin