The hidden quasar nucleus of a WISE-selected, hyperluminous, dust-obscured galaxy at z ~ 2.3

TL;DR

This study presents the first X-ray spectrum of a Hot dust-obscured galaxy at z ~ 2.3, revealing a reflection-dominated, Compton-thick AGN with significant star formation, supporting models of co-evolving luminous quasars and massive galaxies.

Contribution

It provides the first X-ray spectral analysis of a Hot DOG, confirming its Compton-thick AGN nature and quantifying its star formation and quasar contribution.

Findings

X-ray spectrum shows a flat continuum indicative of heavy obscuration.

The intrinsic luminosity of the AGN is estimated to be >~ 5 x 10^45 erg/s.

Star formation rate is approximately 2100 solar masses per year.

Abstract

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 (>= 10^47 erg/s), dust-enshrouded objects at z > 2 recently discovered in the WISE All Sky Survey. The 40 ks XMM-Newton spectrum reveals a continuum as flat (Gamma ~ 0.8) as typically seen in heavily obscured AGN. This, along with the presence of strong Fe Kalpha emission, clearly suggests a reflection-dominated spectrum due to Compton-thick absorption. In this scenario, the observed luminosity of L(2-10 keV) ~ 2 x 10^44 erg/s is a fraction (<10%) of the intrinsic one, which is estimated to be >~ 5 x 10^45 erg/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 (~ 2100 Msun/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.