NuSTAR Discovery of a Compton-thick Dust-obscured Galaxy WISE J0825+3002

TL;DR

This paper reports the discovery of a Compton-thick, dust-obscured galaxy at redshift 0.89 using NuSTAR, revealing an actively growing black hole with high gas and dust content, and confirming empirical relations between luminosity ratios and Eddington ratio.

Contribution

First detection of a mildly Compton-thick dust-obscured galaxy at z=0.89 with detailed X-ray and SED analysis, confirming known AGN luminosity relations.

Findings

Hydrogen column density indicates a mildly Compton-thick AGN.

X-ray luminosity and Eddington ratio suggest active black hole growth.

Luminosity ratio relations align with previous empirical AGN models.

Abstract

We report the discovery of a Compton-thick (CT) dust-obscured galaxy (DOG) at $z$ = 0.89, WISE J082501.48+300257.2 (WISE0825+3002), observed by Nuclear Spectroscopic Telescope Array (NuSTAR). X-ray analysis with the XCLUMPY model revealed that hard X-ray luminosity in the rest-frame 2-10 keV band of WISE0825+3002 is $L_{\rm X}$ (2-10 keV) = $4.2^{+2.8}_{-1.6} \times 10^{44}$ erg s$^{-1}$ while its hydrogen column density is $N_{\rm H}$ = $1.0^{+0.8}_{-0.4} \times 10^{24}$ cm$^{-2}$, indicating that WISE0825+3002 is a mildly CT active galactic nucleus (AGN). We performed the spectral energy distribution (SED) fitting with CIGALE to derive its stellar mass, star formation rate, and infrared luminosity. The estimated Eddington ratio based on stellar mass and integration of the best-fit SED of AGN component is $\lambda_{\rm Edd}$ = 0.70, which suggests that WISE0825+3002 harbors an actively growing black hole behind a large amount of gas and dust. We found that the relationship between luminosity ratio of X-ray and 6 $\mu$m, and Eddington ratio follows an empirical relation for AGNs reported by Toba et al. (2019a).