Scientific Seminars

Properties and evolution of early-type galaxies at z~1.3 - Lynx supercluster

Anand Raichoor
INAF-OABrera

2010-12-15    14:00    Brera - Cupola Fiore

We probe the influence of the mass and of the environment on the evolution of early-type galaxies at z~1.3, together with their size evolution. This study relies on optical/near-infrared (0.6-4.5 microns) imaging of the Lynx supercluster, which is a structure at z~1.3 constituted of two clusters and at least three groups, all of them spectroscopically confirmed. By adding GOODS/CDFS data, we built a sample of 58 early-type galaxies at z~1.3 belonging to three different environments (cluster, group and field). We study the influence of the stellar population model used (Bruzual & Charlot 2003, Maraston 2005, Charlot & Bruzual, in preparation) when estimating the mass and the age through SED fitting and conclude that significant differences are still present, because of the different modeling of the TP-AGB phase. However, according to all models, the most massive galaxies are the oldest ones. According to Maraston 2005 and Charlot & Bruzual (in prep.) models, though that the mass distributions are similar in the clusters and in the groups, cluster galaxies are slightly older than the group ones. Concerning field galaxies, our sample is almost free of massive (M > 10^11 Msun) galaxies: they are on average younger than the cluster/group ones. We study the Kormendy relation (size vs. surface brightness), which is already in place ate z~1.3 and shows no dependence on the environment. In addition, numerous recent works mentioned the existence of very compact galaxies at z~1-2. With the building of the mass-size diagram, we conclude that the model used and the age of the considered galaxies significantly affects the conclusions.