XMM-Newton observations of Extremely Red Objects and the link with luminous, X-ray obscured quasars

We present the results of a deep ( about 80 ks) XMM-Newton survey of the largest sample of near-infrared selected Extremely Red Objects (R - K > 5) available to date to K-S less than or similar to 19.2. At the relatively bright X-ray fluxes ( F2-10 keV greater than or similar to 4 x 10(-15) erg cm(-2) s(-1)) and near-infrared magnitude probed by the present observations, the fraction of AGN ( i.e. X-ray detected) among the ERO population is small (similar to 3.5%); conversely, the fraction of EROs among hard X- ray selected sources is much higher (similar to 20%). The X- ray properties of EROs detected in our XMM-Newton observation indicate absorption in excess of 10(22) cm(-2) in a large fraction of them. We have also considered additional samples of X- ray detected EROs available in the literature. X- ray spectral analysis of the highest S/N sources unambiguously indicates that large columns of cold gas ( even > 10(23) cm(-2)) are the rule rather than the exception. The X-ray, optical and near- infrared properties of those X- ray selected EROs with a spectroscopic or photometric redshift nicely match those expected for type 2 quasars, the high-luminosity, high-redshift obscured AGNs predicted in baseline XRB synthesis models. A close correlation is detected between X- and K-band fluxes. For the AGN EROs this is consistent, under reasonable assumptions, with the relation established locally between the host galaxies and their central black holes. This suggests that the majority of EROs are powered by massive black holes accreting, on average, at about 0.03- 0.1 of the Eddington limit.