Abstract:Hot dust-obscured galaxies (Hot DOGs) are a rare population of hyper-luminous infrared galaxies revealed by WISE from their very red mid-IR colors. Their high luminosities are dominated by the emission of hot dust (T > 60 K). Multi-wavelength studies have shown clear evidence that these objects at 1.6< z < 4.6 are powered by highly dust-obscured AGN. Hot DOGs are likely to represent a special evolutionary stage connecting obscured and unobscured quasars, marking the period of the most rapid SMBH growth and greatest quasar feedback. Such an evolutionary stage may exist at all redshifts.We have recently discovered a highly obscured AGN at z ~ 0.4 hidden in a starburst galaxy. Its well-sampled SED from UV to far-IR wavelengths and emission line features resemble the observed properties of high-z Hot DOGs. Our recent NuSTAR and VLBA observations also confirm their close similarities. This system is a perfect local analog of its high-redshift siblings and an excellent laboratory for investigating the transitional obscured-to-unobscured phase of the AGN evolution. The importance and implications of finding the low-z obscured AGNs will be discussed.
Bio:Dr. Chao-Wei Tsai is a research scientist in the radio astronomy division of National Astronomical Observatories, Chinese Academy of Sciences. He received his BS in Physics from Taiwan University, MS in Astronomy from Central University, and PhD in Astronomy from the 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 radio galaxies that may contain a binary supermassive black hole.