SPECTROPOLARIMETRIC EVIDENCE FOR RADIATIVELY INEFFICIENT ACCRETION IN AN OPTICALLY DULL ACTIVE GALAXY

Journal Article · Sun May 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/732/1/23· OSTI ID:21574655

Trump, Jonathan R ^[1]; Nagao, Tohru; Ikeda, Hiro ^[2]; Murayama, Takashi; Taniguchi, Yoshi ^[3]; Impey, Christopher D ^[4]; Stocke, John T ^[5]; Civano, Francesca; Elvis, Martin; Kelly, Brandon C ^[6]; Jahnke, Knud ^[7]; Koekemoer, Anton M ^[8]

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1. University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
2. Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)
3. Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai 980-8578 (Japan)
4. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
5. Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, UCB-389, University of Colorado, Boulder, CO 80309 (United States)
6. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
7. Max Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
8. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

We present Subaru/FOCAS spectropolarimetry of two active galaxies in the Cosmic Evolution Survey. These objects were selected to be optically dull, with the bright X-ray emission of an active galactic nucleus (AGN) but missing optical emission lines in our previous spectroscopy. Our new observations show that one target has very weak emission lines consistent with an optically dull AGN, while the other object has strong emission lines typical of a host-diluted Type 2 Seyfert galaxy. In neither source do we observe polarized emission lines, with 3{sigma} upper limits of P{sub BLR} {approx}< 2%. This means that the missing broad emission lines (and weaker narrow emission lines) are not due to simple anisotropic obscuration, e.g., by the canonical AGN torus. The weak-lined optically dull AGN exhibits a blue polarized continuum with P = 0.78% {+-} 0.07% at 4400 A < {lambda}{sub rest} < 7200 A (P = 1.37% {+-} 0.16% at 4400 A < {lambda}{sub rest} < 5050 A). The wavelength dependence of this polarized flux is similar to that of an unobscured AGN continuum and represents the intrinsic AGN emission, either as synchrotron emission or the outer part of an accretion disk reflected by a clumpy dust scatterer. Because this intrinsic AGN emission lacks emission lines, this source is likely to have a radiatively inefficient accretion flow.

• OSTI ID: 21574655
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 732; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ELECTROMAGNETIC RADIATION
EMISSION
GALAXIES
GALAXY NUCLEI
IONIZING RADIATIONS
POLARIZATION
RADIATIONS
SEYFERT GALAXIES
X RADIATION