Low-Luminosity Active Galaxies and Their Central Black Holes

Central black hole masses for 118 spiral galaxies representing morphologicalstages S0/a through Sc and taken from the large spectroscopic survey of Ho,Filippenko & Sargent (1997) are derived using 2MASS Ks data. Black hole (BH)masses are found using a calibrated black-hole - Ks bulge luminosity relation,while bulge luminosities are measured using GALFIT, a two-dimensionalbulge/disk decomposition routine. The BH masses are correlated against a variety of nuclear and host-galaxyproperties. Nuclear properties such as line width and line ratios show a veryhigh degree of correlation with BH mass. The excellent correlation withline-width supports the view that the emission-line gas is in virialequilibrium with either the BH or bulge potential. The very good emission-lineratio correlations may indicate a change in ionizing continuum shape with BHmass in the sense that more massive BHs generate harder spectra. Apart from the inclination-corrected rotational velocity, no excellentcorrelations are found between BH mass and host-galaxy properties. Significant differences are found between the distributions of BH masses inearly-, mid- and later-type spiral galaxies in the sense that early-typegalaxies have preferentially larger central BHs. The line-width distributionsshow a marked difference among the subsamples in the sense that earlier-typegalaxies have larger line widths. There are also clear differences in lineratios between subsamples likely related to the level of ionization in the gas.Finally, a Ks-band Simien & de Vaucouleurs diagram shows excellent agreementwith the original B-band relation.Comment: Accepted by A.