Volume 618, October 2018
|Number of page(s)||11|
|Published online||09 October 2018|
The hyperluminous Compton-thick z ∼ 2 quasar nucleus of the hot DOG W1835+4355 observed by NuSTAR
INAF – Osservatorio Astronomico di Roma, Via di Frascati 33, 00078 Monte Porzio Catone, Italy
2 Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146, Roma, Italy
3 Dipartimento di Fisica e Astronomia (DIFA), Università di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
4 INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
5 Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34143 Trieste, Italy
6 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
7 Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Ave., Cambridge CB3 0HE, UK
8 Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
9 Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
10 Center for Cosmology and AstroParticle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA
11 Centro de Astrobiología (CSIC-INTA), Depto. de Astrofísica, ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Spain
12 Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
13 Chinese Academy of Sciences South America Center for Astronomy and China-Chile Joint Center for Astronomy, Camino El Observatorio 1515, Las Condes, Santiago, Chile
14 Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
Accepted: 29 June 2018
We present a 155 ks 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-Newton 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 ∼3000 M⊙ yr−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.
Key words: X-rays: galaxies / galaxies: active / quasars: general / quasars: individual: WISE J1835+4355
© ESO 2018
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