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Title: UNVEILING A POPULATION OF GALAXIES HARBORING LOW-MASS BLACK HOLES WITH X-RAYS

We report the discovery of three low-mass black hole (BH) candidates residing in the centers of low-mass galaxies at z < 0.3 in the Chandra Deep Field-South Survey. These BHs are initially identified as candidate active galactic nuclei based on their X-ray emission in deep Chandra observations. Multi-wavelength observations are used to strengthen our claim that such emission is powered by an accreting supermassive BH. While the X-ray luminosities are low at L{sub X} {approx} 10{sup 40} erg s{sup -1} (and variable in one case), we argue that they are unlikely to be attributed to star formation based on H{alpha} or UV fluxes. Optical spectroscopy from Keck and the VLT allows us to (1) measure accurate redshifts, (2) confirm their low stellar host mass, (3) investigate the source(s) of photo-ionization, and (4) estimate extinction. With stellar masses of M{sub *} < 3 Multiplication-Sign 10{sup 9} M{sub Sun} determined from Hubble Space Telescope/Advanced Camera for Surveys imaging, the host galaxies are among the lowest mass systems known to host actively accreting BHs. We estimate BH masses M{sub BH} {approx} 2 Multiplication-Sign 10{sup 5} M{sub Sun} based on scaling relations between BH mass and host properties for more luminous systems. In onemore » case, a broad component of the H{alpha} emission-line profile is detected, thus providing a virial mass estimate. BHs in such low-mass galaxies are of considerable interest as the low-redshift analogs to the seeds of the most massive BHs at high redshift which have remained largely elusive to date. Our study highlights the power of deep X-ray surveys to uncover such low-mass systems.« less
Authors:
;  [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8]
  1. Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, the University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8568 (Japan)
  2. Department of Astrophysical Science, Princeton University, Princeton, NJ 08544 (United States)
  3. Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
  4. Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China)
  5. Spitzer Science Center, 314-6 California Institute of Technology, 1201 East California Boulevard, Pasadena, CA 91125 (United States)
  6. Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
  7. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
  8. European Southern Observatory, Karl-Schwarzschild-Strasse 2, Garching, D-85748 (Germany)
Publication Date:
OSTI Identifier:
22130971
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 773; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BALMER LINES; BLACK HOLES; CAMERAS; GALAXY NUCLEI; LUMINOSITY; MASS; RED SHIFT; SCALING; STARS; TELESCOPES; ULTRAVIOLET RADIATION; WAVELENGTHS; X RADIATION