THE ORIGIN OF THE INTRINSIC SCATTER IN THE RELATION BETWEEN BLACK HOLE MASS AND BULGE LUMINOSITY FOR NEARBY ACTIVE GALAXIES

We investigate the origin of the intrinsic scatter in the correlation between black hole mass (M-BH) and bulge luminosity (L-bul) in a sample of 45 massive, local (z less than or similar to 0.35) type 1 active galactic nuclei (AGNs). We derive MBH from published optical spectra assuming a spherical broad-line region, and Lbul from detailed two-dimensional decomposition of archival optical Hubble Space Telescope images. AGNs follow the M-BH-L-bul relation of inactive galaxies, but the zero point is shifted by an average of Delta logM(BH) approximate to 0.3 dex. We show that the magnitude of the zero point offset, which is responsible for the intrinsic scatter in the M-BH-L-bul relation, is correlated with several AGN and host galaxy properties, all of which are ultimately related to, or directly impact, the BH mass accretion rate. At a given bulge luminosity, sources with higher Eddington ratios have lower M-BH. The zero point offset can be explained by a change in the normalization of the virial product used to estimate MBH, in conjunction with modest BH growth (similar to 10%-40%) during the AGN phase. Galaxy mergers and tidal interactions appear to play an important role in regulating AGN fueling in low-redshift AGNs.