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Contribution of Stellar Tidal Disruptions to the X-Ray Luminosity Function of Active Galaxies

Milosavljević, Miloš and Merritt, David and Ho, Luis C. (2006) Contribution of Stellar Tidal Disruptions to the X-Ray Luminosity Function of Active Galaxies. Astrophysical Journal, 652 (1). pp. 120-125. ISSN 0004-637X. doi:10.1086/508134.

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The luminosity function of active galactic nuclei (AGNs) has been measured down to luminosities ~10^(42) ergs s^(-1) in the soft and hard X-rays. Some fraction of this activity is associated with the accretion of the material liberated by the tidal disruption of stars by massive black holes. We estimate the contribution to the X-ray luminosity function from the tidal disruption process. While the contribution depends on a number of poorly known parameters, it appears that it can account for the majority of X-ray-selected AGNs with soft or hard X-ray luminosities ≲10^(43)-10^(44) ergs s^(-1). If this is correct, a significant portion of the X-ray luminosity function of AGNs is comprised of sources powered by tidal disruption at the faint end, while the sources at the bright end are powered by nonstellar accretion. Black holes with masses ≲2 × 10^6 M_☉ could have acquired most of their present mass by an accretion of tidal debris. In view of the considerable theoretical uncertainty concerning the detailed shape of the light curves of tidal disruption events, we focus on power-law luminosity decay (as identified in candidate tidal disruption events), but we also discuss constant accretion rate models. We expect that the sources associated with thin-disk accretion of circularized tidal debris have peak luminosities of ≲10^(39)-10^(41) ergs s^(-1), below the luminosity range probed in present surveys.

Item Type:Article
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Ho, Luis C.0000-0001-6947-5846
Additional Information:© 2006 American Astronomical Society. Received 2006 February 16; accepted 2006 August 3. We would like to thank an anonymous referee for helpful comments and Avishay Gal-Yam, Eran Ofek, Sterl Phinney, and Ohad Shemmer for inspiring discussions. M. M. acknowledges support by NASA through the Hubble Fellowship grant HST-HF-01188.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS5-26555. D. M. acknowledges support by NSF grants AST 04-20920 and AST 04-37519, and NASA grant NNG04GJ48G.
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF-01188.01-A
NSFAST 04-20920
NSFAST 04-37519
Subject Keywords:accretion, accretion disks; black hole physics; cosmology: observations; galaxies: active; galaxies: nuclei
Issue or Number:1
Record Number:CaltechAUTHORS:20110616-112204911
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Official Citation:Contribution of Stellar Tidal Disruptions to the X-Ray Luminosity Function of Active Galaxies Miloš Milosavljević et al. 2006 ApJ 652 120
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24030
Deposited On:16 Jun 2011 20:18
Last Modified:09 Nov 2021 16:20

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