HOT-DUST-POOR TYPE 1 ACTIVE GALACTIC NUCLEI IN THE COSMOS SURVEY

Journal Article · Sat Nov 20 00:00:00 EST 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/724/1/L59· OSTI ID:21452666

Heng, Hao; Elvis, Martin; Civano, Francesca; Lanzuisi, Giorgio ^[1]; Brusa, Marcella; Bongiorno, Angela ^[2]; Lusso, Elisabeta; Zamorani, Gianni; Comastri, Andrea ^[3]; Impey, Chris D; Trump, Jonathan R ^[4]; Koekemoer, Anton M ^[5]; Le Floc'h, Emeric; Sanders, David ^[6]; Salvato, Mara ^[7]; Vignali, Cristian ^[8]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2. Max Planck Institut fuer extraterrestrische Physik Giessenbachstrasse 1, D-85748 Garching (Germany)
3. INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)
4. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
5. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
6. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
7. IPP-Max-Planck-Institute for Plasma Physics, Boltzmannstrasse 2, D-85748 Garching (Germany)
8. Dipartimento di Astronomia, Universita degli Studi di Bologna, via Ranzani 1, I-40127 Bologna (Italy)

We report a sizable class of type 1 active galactic nuclei (AGNs) with unusually weak near-infrared (1-3 {mu}m) emission in the XMM-COSMOS type 1 AGN sample. The fraction of these 'hot-dust-poor' AGNs increases with redshift from 6% at low redshift (z < 2) to 20% at moderate high redshift (2 < z < 3.5). There is no clear trend of the fraction with other parameters: bolometric luminosity, Eddington ratio, black hole mass, and X-ray luminosity. The 3 {mu}m emission relative to the 1 {mu}m emission is a factor of 2-4 smaller than the typical Elvis et al. AGN spectral energy distribution (SED), which indicates a 'torus' covering factor of 2%-29%, a factor of 3-40 smaller than required by unified models. The weak hot dust emission seems to expose an extension of the accretion disk continuum in some of the source SEDs. We estimate the outer edge of their accretion disks to lie at (0.3-2.0) x 10{sup 4} Schwarzschild radii, {approx}10-23 times the gravitational stability radii. Formation scenarios for these sources are discussed.

• OSTI ID: 21452666
• Journal Information: Astrophysical Journal Letters, Vol. 724, Issue 1; Other Information: DOI: 10.1088/2041-8205/724/1/L59; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
BLACK HOLES
BOLOMETERS
COSMOLOGICAL MODELS
DUSTS
EMISSION
ENERGY SPECTRA
GALACTIC EVOLUTION
GALAXIES
GALAXY NUCLEI
LUMINOSITY
MASS
QUASARS
RED SHIFT
SCHWARZSCHILD RADIUS
UNIVERSE
COSMIC RADIO SOURCES
EVOLUTION
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
SPECTRA