发稿时间：2019-05-06浏览次数：212

USTC Astronomy Colloquium Series: 2019 Spring
The Gobbling Monsters within the Hot DOGs
蔡肇伟  研究员
国家天文台
2019/05/07, 4:00pm , the 19th-floor Observatory Hall
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. These hyperluminous sources are likely powered by highly obscured AGNs, and there is no evidence suggesting these systems are beamed or lensed. The measured masses of the monstrous black holes within these Hot DOGs 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. The case of W2246-0526 at z = 4.601 is the most luminous Hot DOG yet identified. With 3.6 x 10^14 L_Sun, it is among the few most luminous galaxies known thus far. Using the broad MgII-2799A emission line and the blueshift-corrected broad CIV line, 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.
 Dr. Chao-Wei Tsai is a research scientist in the radio astronomy division of National Astronomical Observatories, Chinese Academy of Sciences. He received his PhD in Astronomy from University of California, Los Angeles (UCLA). After graduation, he joined the NASA's WISE mid-infrared Sky Survey mission at Caltech's Infrared Processing and Analysis Center and later took his NASA Postdoctoral Program Fellowship at Jet Propulsion Laboratory. Prior to joining NAOC in late 2018, he worked as an assistant researcher at UCLA. He is experienced in multi-wavelength investigations of starburst galaxies and AGNs, emphasizing radio morphology, optical and near-IR spectroscopy, and SED analysis. While working at Caltech and JPL, he co-discovered a new type of highly obscured active galactic nuclei called Hot DOGs, and defined "Extremely Luminous Infrared Galaxies" (ELIRG), a new class of galaxies with luminosity higher than the 10^14 times of the solar value. He has also been leading investigations of other unusual objects found in the WISE Sky Survey, such as dwarf galaxies which are simultaneously very blue in optical light and very red in mid-infrared light, and a radio galaxy which may contain a binary super massive black hole.