Colloquium on Oct. 30th, 2019

The Gobbling Monsters within the Hot DOGs

Speaker: Chao-Wei Tasi 

Venue: Room 2111, SWIFAR Building

Time: 3:00 PM, Wednesday, 30th October, 2019

Abstract: 

Hot, Dust-Obscured Galaxies, or Hot DOGs, are a class of distant dust-enshrouded galaxies with extremely high luminosity, including several "Extremely Luminous Infrared Galaxies" (ELIRGs) that reach 10^14 L_Sun. Selected by their utmost red colors in WISE bands, their SEDs incorporating WISE, Spitzer, and Herschel photometry indicate that hot dust dominates the bolometric luminosity. The SED analysis suggests a close-to-spherical dust distribution with a range of temperatures. These hyperluminous sources are likely powered by highly obscured active galactic nuclei (AGN), and are unlikely to be lensed. The measured masses of the monstrous black holes within these Hot DOGs using MOSFIRE reflects that they are accreting at a rate close to the Eddington limit. This hyperluminous, highly obscured population may represent a special evolutionary stage prior to the red quasar and optical quasar phases. 

In the case of W2246-0526, the most luminous Hot DOG yet identified, its total luminosity of 3.6 x 10^14 L_Sun at z = 4.601 make it well into the Extremely Luminous Infrared Galaxy (ELIRG, > 10^14 L_Sun) range, and among the few most luminous galaxies known thus far. Using the broad MgII-2799A emission line from OSIRIS and the blueshift-corrected broad CIV line from LRIS, we estimate the black hole mass of the obscured AGN to be ~ 4x10^9 M_Sun, and the corresponding Eddington ratio is L_AGN/L_Edd = 2.8. The high Eddington ratio of W2246-0526 may reach the level where the luminosity is saturating due to photon trapping in the accretion flow, and be insensitive to the mass accretion rate. As the result, the black hole mass growth rate could exceed the apparent accretion rate derived from the observed luminosity.