A New Population of Cold Quasars
Abstract
AGNs are the most luminous objects in the universe, and the most massive ones are usually created by the merger of two gas-rich disk galaxies. This gas fuels an AGN through an accretion disk that emits at optical/ultraviolet wavelengths. This accretion disk can be obscured by a dusty torus that emits mostly in the IR waveband. Towards the center of the AGN, an energetic corona emits in the X-Ray waveband. We have identified >1800 X-ray luminous AGN in a 16 deg2 region of the Stripe82 field surveyed by XMM-Newton and Herschel. Given the detection limits of Herschel, only 10% of our AGN have both an X-ray detection and an IR detection, providing unique insight into the fraction of luminous AGN surrounded by an abundance of cold dust. We coin these IR bright, type-1 AGN "cold quasars". We demonstrate that many of these cold quasars are in the canonical coalescence phase by examining SDSS imaging. However, just as many appear to be isolated point sources, challenging the merger scenario. We compare the IR luminosity and X-ray luminosity with less X-ray luminous AGN from z=1-2 (from COSMOS and GOODS-S) and find cold quasars to have proportionally more X-ray emission at a given infrared luminosity. This is likely due to the IR emission arising from the host galaxy, while the X-ray emission comes from the AGN component. We also compare the amount of dust mass in these cold quasars with the dust mass of star formation galaxies at the same redshifts and find it to be comparable. This then supports the picture where the quasar component is just beginning to become luminous, but has not blown out any of the host galaxy gas and dust.
- Publication:
-
American Astronomical Society Meeting Abstracts #234
- Pub Date:
- June 2019
- Bibcode:
- 2019AAS...23430604C