Mathematics – Logic
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21331606w&link_type=abstract
American Astronomical Society, AAS Meeting #213, #316.06; Bulletin of the American Astronomical Society, Vol. 41, p.294
Mathematics
Logic
Scientific paper
To investigate the dependence of AGN activity on host galaxy properties and environment, we compare AGN host galaxies with non-AGN galaxies at matched luminosity, velocity dispersion, color, color gradient, or concentration index, using 140,000 galaxies, including 5000 AGN host galaxies, selected from SDSS DR5. First, we find that AGNs are dominantly hosted by intermediate-mass late-type galaxies while, among most massive galaxies AGNs are preferentially present in early-type galaxies. The AGN fraction (fAGN) increases with galaxy luminosity at given velocity dispersion. At fixed luminosity, however, the AGN fraction of early-types monotonically decreases with velocity dispersion, while the AGN fraction of late-types peaks at intermediate velocity dispersion, indicating a clear dependence on the host morphology. For both morphological types, galaxies with intermediate color show higher fAGN than bluer and redder color galaxies. Second, we investigate how the accretion power varies with galaxy properties. While the Eddington ratio ([OIII] line luminosity normalized by black hole mass) ranges over three orders of magnitude for both morphological types, late-types in general host more powerful AGNs. These results are consistent with a scenario that more massive, redder, and more concentrated early-type and late-type galaxies are harder to host AGNs since these galaxies already consumed gas at the center or do not have sufficient gas supply mechanism to the center. In contrast, intermediate-mass, intermediate-color, and more concentrated late-type galaxies are more likely to host AGNs since some fraction of low-mass, blue, and less concentrated late-type galaxies may not host massive black holes or may host very low-power AGNs. Finally, we find that the AGN fraction is higher for late-type galaxies when a spiral neighbor is present within the virial radius, implying that fuel supply from a neighbor is crucial for triggering AGN activity.
Choi Yemon
Park Chan
Woo Jong-Hak
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