Infrared Contributions of X-Ray Selected Active Galactic Nuclei in Dusty Star-Forming Galaxies

Arianna Brown, Hooshang Nayyeri, Asantha Cooray, Jingzhe Ma, Ryan C. Hickox, Mojegan Azadi

Published 2018-01-07Version 1

We investigate the infrared contribution from supermassive black hole activity versus host galaxy emission in the mid to far-infrared (IR) spectrum for a large sample of X-ray bright active galactic nuclei (AGN) residing in dusty, star-forming host galaxies. We select 703 AGN with L_X = 10^42-46 ergs s^-1 at 0.1 < z < 5 from the Chandra XBootes X-ray Survey with rich multi-band observations in the optical to far-IR, including a required detection in the Spitzer MIPS 24 um band and at least one in a Herschel far-IR band. This is the largest sample to date of X-ray AGN with mid- and far-IR detections that uses spectral energy distribution (SED) decomposition to determine intrinsic AGN and host galaxy infrared luminosities. We observe weak or nonexistent relationships when averaging star-formation luminosities in bins of AGN luminosities, but see stronger positive trends when averaging L_X in bins of star-forming luminosity for AGN at low redshifts. We determine an average dust covering factor of 33%, corresponding to a Type 2 population of roughly a third. We see no strong connection between AGN fractions in the IR and corresponding total infrared, 24 um, or X-ray luminosities. The average rest-frame AGN contribution as a function of IR wavelength shows significant (~80%) contributions in the mid-IR that trail off at lambda > 30 um. Additionally, we provide an equation relating L_X and pure AGN IR output for high-z AGN allowing future studies to estimate AGN infrared contribution using only X-ray flux density estimates.