The manifold spectra and morphologies of EROs

Deep VLT optical spectroscopy, HST+ACS (GOODS) imaging and VLA observations are used to unveil the nature of a complete sample of 47 EROs with R−Ks > 5a ndKs < 20. The spectroscopic redshift completeness is 62%. Morphological classification was derived for each ERO through visual inspection and surface brightness profile fitting. Three main ERO morphological types are found: E/S0 galaxies (∼30−37%), spiral-like (∼24−46%) and irregular systems (∼17−39%). The only ERO detected in the radio is likely to host an obscured AGN. The average radio luminosity of the star-forming EROs undetected in the radio implies star formation rates of the order of ∼33 Myr −1 . The colors, redshifts and masses of the E/S0 galaxy subsample imply a minimum formation redshift zf ∼ 2. With this zf there is enough time to have old and massive stellar spheroids already assembled at z ∼ 1. We verify that the R − Ks vs. J − Ks color diagram is efficient in segregating old and dusty-star-forming EROs.