2015A&A...574L...9P

We present the first X-ray spectrum of a hot dust-obscured galaxy (DOG), namely W1835+4355 at z∼2.3. Hot DOGs represent a very rare population of hyperluminous (≥10⁴⁷erg/s), dust-enshrouded objects at z≥2 recently discovered in the WISE All Sky Survey. The 40ks XMM-Newton spectrum reveals a continuum as flat (Γ∼0.8) as typically seen in heavily obscured AGN. This, along with the presence of strong Fe Kα emission, clearly suggests a reflection-dominated spectrum due to Compton-thick absorption. In this scenario, the observed luminosity of L_2–10∼2x10⁴⁴erg/s is a fraction (<10%) of the intrinsic one, which is estimated to be >5x10⁴⁵erg/s by using several proxies. The Herschel data allow us to constrain the SED up to the sub-mm band, providing a reliable estimate of the quasar contribution (∼75%) to the IR luminosity as well as the amount of star formation (∼2100M_☉/yr). Our results thus provide additional pieces of evidence that associate Hot DOGs with an exceptionally dusty phase during which luminous quasars and massive galaxies co-evolve and a very efficient and powerful AGN-driven feedback mechanism is predicted by models.