The Accretion History of AGN: The Spectral Energy Distributions of X-ray Luminous AGN

Abstract

Spectral energy distributions (SEDs) from X-ray to far-infrared (FIR) wavelengths are presented for a sample of 1246 X-ray luminous active galactic nuclei (AGN; \(L_{0.5-10\rm{keV}}>10^{43}\) erg s\(^{-1}\)), with \(z_{\rm{spec}}<1.2\), selected from Stripe 82X, COSMOS, and GOODS-N/S. The rest-frame SEDs show a wide spread (\(\sim2.5\) dex) in the relative strengths of broad continuum features at X-ray, ultraviolet (UV), mid-infrared (MIR), and FIR wavelengths. A linear correlation (log-log slope of 0.7\(\pm0.04\)) is found between \(L_{\rm{MIR}}\) and \(L_{\rm{X}}\). There is significant scatter in the relation between the \(L_{\rm{UV}}\) and \(L_{\rm{X}}\) due to heavy obscuration, however the most luminous and unobscured AGN show a linear correlation (log-log slope of 0.8\(\pm0.06\)) in the relation above this scatter. The relation between \(L_{\rm{FIR}}\) and \(L_{\rm{X}}\) is predominantly flat, but with decreasing dispersion at \(L_{\rm{X}}>10^{44}\) erg s\(^{-1}\). The ratio between the "galaxy subtracted" bolometric luminosity and the intrinsic \(L_{\rm{X}}\) increases from a factor of \(\sim\)$10-70\( from log \)L_{\rm{bol}}/{\rm(erg\; s}^{-1})=44.5-46.5\(. Characteristic SED shapes have been determined by grouping AGN based on relative strengths of the UV and MIR emission. The average \)L_{1\mu\rm{m}}\( is constant for the majority of these SED shapes, while AGN with the strongest UV and MIR emission have elevated \)L_{1\mu\rm{m}}\(, consistent with the AGN emission dominating their SEDs at optical and NIR wavelengths. A strong correlation is found between the SED shape and both the \)L_{\rm{X}}\( and \)L_{\rm{bol}}\(, such that \)L_{\rm{bol}}/L_{\rm{X}}=20.4\pm1.8\(, independent of the SED shape. This is consistent with an evolutionary scenario of increasing \)L_{\rm{bol}}$ with decreasing obscuration as the AGN blows away circumnuclear gas.