X-ray spectral properties of dust-obscured galaxies in the XMM-SERVS coverage of the XMM-LSS field

Abstract

With an aim to unveil the population of obscured AGN hosted in high-$z$ dust-obscured galaxies (DOGs), we performed X-ray spectral study of $34$ DOGs ($0.59$ $\leq$ $z$ $\leq$ $4.65$) lying within $5.3$ deg$^{2}$ of the XMM-SERVS coverage in the XMM-LSS field. To improve the spectral quality of individual sources, we combined all the existing $\textit{XMM-Newton}$ data and also included $\textit{Chandra}$/ACIS data, whenever available. We find that the X-ray spectra of our DOGs can be fitted with a simple absorbed power law or with a physically-motivated BORUS02 model. The line-of-sight column densities ($N_{\textrm{H}}$) in our sources span across a wide range ($1.02$ $\times$ $10^{22}$ cm$^{-2}$ $\leq$ $N_{\textrm{H}}$ $\leq$ $1.21$ $\times$ $10^{24}$ cm$^{-2}$), with a substantial fraction ($\sim$ $17.6$ per cent) of them being heavily obscured ($N_{\textrm{H}}$ $\geq$ $10^{23}$ cm$^{-2}$). We also identified one new CT-AGN candidate, yielding the CT-AGN fraction in our sample to be only $3$ per cent. The absorption-corrected $2.0-10$ keV X-ray luminosities of our sources ($2.00~\times~10^{43}$ erg s$^{-1}$ $\leq$ $L_{\textrm{2-10 keV}}^{\textrm{int}}$ $\leq$ $6.17~\times~10^{45}$ erg s$^{-1}$) suggest them to be luminous quasars. The $N_{\textrm{H}}$ versus Eddington ratio diagnostic plot infers that our sample consists of a heterogeneous population that includes a small fraction ($\sim$ $12$ per cent) of DOGs belonging to an early phase (Hot DOGs) during which accretion and obscuration peaks, while the remaining DOGs belong to an intermediate or late phase during which radiative feedback from the dominant AGN blows away surrounding obscuring material.