AHA: Understanding the Far-IR Properties of X-ray Selected IR-Faint AGN

We aim to determine the intrinsic far-Infrared (far-IR) emission of unobscured quasars over cosmic time. Using a 16 deg² region of the Stripe 82 field surveyed by XMM-Newton and Herschel, we identify 2905 X-ray luminous Active Galactic Nuclei (AGN) from z = 0-3. However, only 10 percent of our AGN are detected both in the X-ray and IR, where the IR is necessary to constrain host galaxy properties such as star formation rate and gas mass. On the other hand, our understanding of the Interstellar Medium (ISM) in the other 90 percent of sources is limited. Because our sample is undetected in the far-IR, we stack Herschel/SPIRE maps to determine the median flux of our sources separated into bins of X-ray luminosity and redshift. We create median Spectral Energy Distributions (SEDs) from the optical to the far-IR for our stacked sources, and we measure the median star formation rate, dust mass, and AGN bolometric luminosity. We find that unobscured quasars on average have increasing SFRs with increasing bolometric luminosity, and this relationship is insensitive to redshift. Unobscured quasars surprisingly have similar dust masses as IR detected sources at the same X-ray luminosity. However, some stacked sources fall below the main sequence of star formation, indicating a lower star formation efficiency. This suggests that these AGN are beginning to quench star formation, but this quenching does not appear to be due to any dissipation of the ISM.