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Paper: An Improved Black Hole Mass–Bulge Luminosity Relationship for AGNs
Volume: 419, Galaxy Evolution: Emerging Insights and Future Challenges
Page: 388
Authors: Gaskell, C. M.; Kormendy, J.
Abstract: Two effects have substantially increased the scatter in the AGN black hole mass–host galaxy bulge luminosity relationship derived from SDSS spectra. The first is that at a fixed black hole mass, M, the SDSS spectrum depends strongly on redshift because an SDSS fiber sees a larger fraction of the total light of more distant galaxies. The second is that at a given redshift, the fraction of host-galaxy light in the fiber increases with decreasing galaxy luminosity. We illustrate the latter effect using the Kormendy et al. (2009) light profiles of Virgo ellipticals. With allowance for the two effects, we obtain a black hole mass—bulge luminosity (MLhost) relationship for AGNs which has a scatter of only ±0.23 dex in mass. This is less than the scatter found for inactive galaxies, and is consistent with the measuring errors. We show that there is a corresponding tight linear relationship between the fraction of host galaxy light in AGN spectra, Lhost / LAGN, and the Eddington ratio, L / LEdd. This linearity implies that at a given M, host luminosities of high-accretion-rate AGNs (NLS1s) and low-accretion-rate AGNs are similar. The Lhost / LAGNL / LEdd relationship provides a simple means of estimating the fraction of host galaxy light in AGN spectra. This means that the real amplitude of variability of low-accretion-rate AGNs is increased relative to NLS1s.
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