The black hole-bulge relationship in luminous broad-line active galactic nuclei and host galaxies

We have measured the stellar velocity dispersions (σ _*) and estimated the central black hole (BH) masses for over 900 broad-line active galactic nuclei (AGNs) observed with the Sloan Digital Sky Survey. The sample includes objects which have redshifts up to z = 0.452, high-quality spectra, and host galaxy spectra dominated by an early-type (bulge) component. The AGN and host galaxy spectral components were decomposed using an eigenspectrum technique. The BH masses (M _BH) were estimated from the AGN broad-line widths, and the velocity dispersions were measured from the stellar absorption spectra of the host galaxies. The range of black hole masses covered by the sample is approximately 10⁶ < M _BH < 10⁹ M _⊙. The host galaxy luminosity-velocity dispersion relationship follows the well-known Faber-Jackson relation for early-type galaxies, with a power-law slope 4.33 0.21. The estimated BH masses are correlated with both the host luminosities (L_H ) and the stellar velocity dispersions (σ_*), similar to the relationships found for low-redshift, bulge-dominated galaxies. The intrinsic scatters in the correlations are large (0.4 dex), but the very large sample size allows tight constraints to be placed on the mean relationships: M _BH L ^0.730.05 _H and M _BH σ^3.340.24 _*. The amplitude of the M _BH- σ_* relation depends on the estimated Eddington ratio, such that objects with larger Eddington ratios have smaller black hole masses than expected at a given velocity dispersion. While this dependence is probably caused at least in part by sample selection effects, it can account for the intrinsic scatter in the M _BH-σ_* relation, and may tie together the accretion rate with physical properties of the host bulge component. We find no significant evolution in the M _BH- σ_* relation with redshift, up to z 0.4, after controlling for possible dependences on other variables. Interested readers can contact the authors to obtain the eigenspectrum decomposition coefficients of our objects.