Hot Dust-Obscured Galaxies with Excess Blue Light

• Published in: arXiv.org 2020-06
• Main Authors: Assef, R J, Brightman, M, Walton, D J, Stern, D, Bauer, F E, Blain, A W, Diaz-Santos, T, Eisenhardt, P R M, Hickox, R C, Jun, H D, Psychogyios, A, C -W Tsai, Wu, J W
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Cosmic dust; Emission analysis; Galaxies; Line of sight; Star formation; Universe
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1905.04320

Hot Dust-Obscured Galaxies (Hot DOGs) are among the most luminous galaxies in the Universe. Powered by highly obscured, possibly Compton-thick, active galactic nuclei (AGNs), Hot DOGs are characterized by SEDs that are very red in the mid-IR yet dominated by the host galaxy stellar emission in the UV and optical. An earlier study identified a sub-sample of Hot DOGs with significantly enhanced UV emission. One target, W0204-0506, was studied in detail and, based on Chandra observations, it was concluded that the enhanced emission was most likely due to either extreme unobscured star-formation (\({\rm SFR}>1000~M_{\odot}~\rm yr^{-1}\)) or to light from the highly obscured AGN scattered by gas or dust into our line of sight. Here, we present a follow-up study of W0204-0506 as well as two more Hot DOGs with excess UV emission. For the two new objects we obtained Chandra/ACIS-S observations, and for all three targets we obtained HST/WFC3 F555W and F160W imaging. We conclude that the excess UV emission is primarily dominated by light from the central highly obscured, hyper-luminous AGN that has been scattered into our line of sight. We cannot rule out, however, that star-formation may significantly contribute to the UV excess of W0204-0506.