paper

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

arXiv:1801.02233 · doi:10.3847/1538-4357/aaf73b

Abstract

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 at 0.1 < z < 5 from the Chandra XBootes X-ray Survey with rich multi-band observations in the optical to far-IR. 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 determine weak or nonexistent relationships when averaging star-formation activity as a function of AGN activity, but see stronger positive trends when averaging L_X in bins of star-forming activity for AGN at low redshifts. We estimate an average dust covering factor of 33% based on infrared SEDs and bolometric AGN luminosity, corresponding to a Type 2 AGN population of roughly a third. We also see a population of AGN that challenge the inclination based unification model with individual dust covering factors that contradict the nuclear obscuration expected from observed X-ray hardness ratios. 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 a relation between observed L_X and pure AGN IR output for high-z AGN allowing future studies to estimate AGN infrared contribution using only observed X-ray flux density estimates.

arXiv commentApJ accepted in Jan

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