The hyperluminous Compton-Thick z ∼ 2 quasar nucleus of the hot DOG W1835+4355 observed by NuSTAR

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Zappacosta, L 
Piconcelli, E 
Duras, F 
Vignali, C 
Valiante, R 

We present a 155ks NuSTAR observation of the z∼2 hot dust-obscured galaxy (hot DOG) W1835+4355. We extracted spectra from the two NuSTAR detectors and analyzed them jointly with the archival XMM PN and MOS spectra. We performed a spectroscopic analysis based on both phenomenological and physically motivated models employing toroidal and spherical geometry for the obscurer. In all the modelings, the source exhibits a Compton-thick column density NH≳1024 cm−2, a 2-10 keV luminosity L2−10≈2×1045 erg s−1 , and a prominent soft excess (∼5−10 % of the primary radiative output), which translates into a luminosity ∼1044 erg s−1. We modeled the spectral energy distribution from 1.6 to 850 μm using a clumpy two-phase dusty torus model plus a modified blackbody to account for emission powered by star formation in the far-infrared. We employed several geometrical configurations consistent with those applied in the X-ray analysis. In all cases we obtained a bolometric luminosity Lbol≈3−5×1047 erg s−1, which confirms the hyperluminous nature of this active galactic nucleus. Finally, we estimate a prodigious star formation rate of $\sim$3000 Myr−1, which is consistent with the rates inferred for z≈2−4 hyperluminous type I quasars. The heavily obscured nature, together with Lbol, the ratio of X-ray to mid-infrared luminosity, the rest-frame optical morphology, and the host star formation rate are indicative of its evolutionary stage. We can interpret this as a late-stage merger event in the transitional, dust-enshrouded, evolutionary phase eventually leading to an optically bright AGN.

X-rays: galaxies, galaxies: active, quasars: general, quasars: individual: WISE J1835+4355
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Astronomy and Astrophysics
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EDP Sciences
Science and Technology Facilities Council (ST/M001172/1)
European Research Council (695671)