Properties of a Large Sample of ERO’s

Abstract

We investigate the properties of a large sample of extremely red objects (∼ 500 EROs) based on deep optical and IR datasets from the CDF-South and HDFs. The ERO’s surface density is consistent with a monolithic model where ellipticals form between 2≤zform≤2.5, while semi-analytic models (SAM) underestimate the density by a factor of 2 to 10. Additional observations (clustering and comoving number density), independent of color modeling, are in good agreement with the expected properties of ellipticals in a hierarchical ΛCDM scenario. This comparison can suggest that SAM provide good predictions for the dark matter haloes assembling while it cannot describe the baryon assembling (star formation) of this extreme population.

Finally, we speculate about the descendants and ancestors of EROs. In the framework of CDM paradigm, the EROs could be the already assembled progenitors of local ellipticals. The brightest population of Lyman Break Galaxies at z∼3 could go through an ERO stage, while it should not be the case for the bulk of the LBGs (faintest samples) unless they undergo major merging events between z∼3 and z∼1.