Galaxy properties in clusters: dependence on the environment and the cluster identification techniques*
Instituto de Astronomía Teórica y Experimental IATE, CONICET, Laprida 922, X5000BGR, Córdoba, Argentina e-mail: [vcoenda;hernan]@.mail.oac.uncor.edu
2 Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, X5000BGR, Córdoba, Argentina
Accepted: 10 June 2009
Aims. We investigate the dependence of several galaxy properties on the environment and cluster identification techniques.
Methods. We select clusters of galaxies from two catalogues based on the SDSS: the ROSAT-SDSS galaxy cluster survey, which is an X-ray selected cluster sample and the MaxBCG catalogue, in which clusters are optically selected. Based on a volume limited sample of galaxies drawn from the spectroscopic DR5 SDSS, we constructed sub-samples of clusters of galaxies with more than ten members. Scaling relations as well as segregation of galaxy properties as a function of the normalized clustocentric radii are analyzed. The properties of galaxies in clusters are compared with those of field galaxies.
Results. Galaxies in X-ray and MaxBCG selected clusters show similar size-luminosity relations. At equal luminosity, late type galaxies in the field have sizes smaller than cluster galaxies of the same morphological type. The Faber-Jackson relation for early-type galaxies in clusters is also the same for X-ray selected and MaxBCG clusters. We found clear differences between the dynamical properties of galaxies in clusters, the brightest cluster galaxies (BCGs) and field galaxies. Using several criteria to classify galaxies into morphological types, we reproduce the well know morphological segregation. The correlation is up to . For the whole range of clustocentric distances, X-ray selected clusters present a higher fraction of early type galaxies than MaxBCG clusters. We also found that bright galaxies preferentially inhabit the cluster centers. Median sizes of galaxies, such as the radius that encloses of Petrosian flux r50, present a behaviour that also depends on the cluster selection criteria. For galaxies in X-ray selected clusters, median values of r50 decrease as goes to zero, whereas the opposite is observed for galaxies in the MaxBCG clusters. These different behaviours are mainly due to early type galaxies. The results are discussed in terms of the different processes that affect the evolution of galaxies in different environments.
Key words: galaxies: clusters / catalogs / general / galaxies: fundamental parameters / X-rays: galaxies: clusters
© ESO, 2009