Constraining the Mass Assembly in Ellipticals from ERO Clustering

Abstract.

The redshift evolution of clustering is a powerful tool to constrain the models of galaxy assembly. In particular, the strong clustering of EROs, if mainly due to early type galaxies, suggests a nearly constant comoving correlation length for this population of galaxies from z=0 to $z\sim1$, in apparent agreement with hierarchical scenarios. However, our recent spectroscopic identifications of a large ERO sample has shown a large fraction of EROs to be dust-reddened star-forming galaxies. We present here a real space clustering analysis of both EROs species that confirm the early-type EROs to be the source of ERO clustering, with dusty star-forming EROs being relatively uncorrelated. Despite the success on accounting for the clustering evolution, we discuss how hierarchical models still fail in reproducing the high comoving density and old ages of early-type galaxies.

The collaborators in the K20 survey include T. Broadhurst (HUJ), A. Cimatti (Arcetri), S. Cristiani (ECF & Trieste), S. D’Odorico (ESO), A. Fontana (Roma), E. Giallongo (Roma), R. Gilmozzi (ESO), N. Menci (Roma), M. Mignoli (Bologna), F. Poli (Roma), L. Pozzetti (Bologna), S. Randich (Arcetri), A. Renzini (ESO), P. Saracco (Milano), J. Vernet (Arcetri), G. Zamorani (Bologna)