Multiwavelength Spectral Energy Distribution Analysis of X-Ray Selected Active Galactic Nuclei at z = 0.2–0.8 in the Stripe 82 Region

Abstract

We perform a systematic, multiwavelength spectral energy distribution (SED) analysis of X-ray detected active galactic nuclei (AGNs) at z = 0.2–0.8 with Sloan Digital Sky Survey (SDSS) counterparts in the Stripe 82 region, consisting of 60 type 1 and 137 type 2 AGNs covering a 2–10 keV luminosity range of $41.6\lt \mathrm{log}\ {L}_{{\rm{x}}}\lt 44.7$ . The latest CIGALE code, where dusty polar components are included, is employed. To obtain reliable host and AGN parameters in type 1 AGNs, we utilize the image-decomposed optical SEDs of host galaxies by Li et al. based on the Subaru Hyper-Suprime Cam images. The mean ratio of black hole masses ( M _BH ) and stellar masses ( M _stellar ) of our X-ray detected type 1 AGN sample, $\mathrm{log}({M}_{\mathrm{BH}}/{M}_{\mathrm{stellar}})=-2.7\pm 0.5$ , is close to the local relation between BH and stellar masses as reported by Li et al. for SDSS quasars. This ratio is slightly lower than that found for more luminous ( $\mathrm{log}{L}_{\mathrm{bol}}\gt 45$ ) type 1 AGNs at z ∼ 1.5. This can be explained by the AGN luminosity dependence of $\mathrm{log}({M}_{\mathrm{BH}}/{M}_{\mathrm{stellar}})$ , which little evolves with redshift. We confirm the trend that the UV-to-X-ray slope ( α _OX ) or X-ray-to-bolometric correction factor ( κ _2–10 ) increases with AGN luminosity or Eddington ratio. We find that type 1 and type 2 AGNs with the same luminosity ranges share similar host stellar mass distributions, whereas type 2s tend to show smaller AGN luminosities than type 1s. This supports the luminosity-dependent (or Eddington-ratio-dependent) unified scheme.

Keywords

• Active galactic nuclei
• Supermassive black holes
• Active galaxies