ar X iv : a st ro - p h / 05 10 69 4 v 1 2 4 O ct 2 00 5 Low - luminosity Active Galaxies and their Central Black Holes

Central black hole masses for 118 spiral galaxies representing morphological stages S0/a through Sc and taken from the large spectroscopic survey of Ho et al. (1997) are derived using K s-band data from 2MASS. Black hole masses are found using a calibrated black-hole – K s bulge luminosity relation, while bulge lumi-nosities are measured by means of a two-dimensional bulge/disk decomposition routine. The black hole masses are correlated against a variety of parameters representing properties of the nucleus and host galaxy. Nuclear properties such as line width (FWHM([N II])), as well as emission-line ratios (e.g., [O III]/Hβ, [O I]/Hα, [N II]/Hα, and [S II]/Hα), show a very high degree of correlation with black-hole mass. The excellent correlation with line-width supports the view that the emission-line gas is in virial equilibrium with either the black hole or bulge potential. The very good emission-line ratio correlations may indicate a change in ionizing continuum shape with black hole mass in the sense that more massive black holes generate harder spectra. Apart from the inclination-corrected rotational velocity, no excellent correlations are found between black-hole mass and host-galaxy properties. Significant differences are found between the distributions of black hole masses in early-, mid-and later-type spiral galaxies (subsamples A, B and C) in the sense that early-type galaxies have preferentially larger central black holes, consistent with observations that Seyfert galaxies are found preferentially in early-type systems. The line-width distributions show a marked difference among subsamples A, B and C, in the sense that earlier-type galaxies have larger line widths. There are also clear differences in line ratios between subsamples A+B and C that likely are related to the level of ionization in the gas. Finally, a K s-band Simien & de Vaucouleurs diagram shows excellent agreement with the original B-band relation, though there is a large dispersion at a given morphological stage. – 2 –