Axisymmetric, three-integral models of galaxies: A massive black hole in NGC 3379

We fit axisymmetric three-integral dynamical models to NGC 3379 using the l ine-of-sight velocity distribution obtained from Hubble Space Telescope FOS spectra of the galaxy center and ground-based long-slit spectroscopy along four position angles, with the light distribution constrained by WFPC2 and ground-based images. We have fitted models with inclinations from 29 degre es (intrinsic galaxy type E5) to 90 degrees (intrinsic E1) and black hole m asses from 0 to 10(9) M-.. The best-fit black hole masses range from 6 x 10 (7) to 2 x 10(8) M-., depending on inclination. The preferred inclination i s 90 degrees (edge-on); however, the constraints on allowed inclination are not very strong, owing to our assumption of constant M/L-v. The velocity e llipsoid of the best model is not consistent with either isotropy or a two- integral distribution function. Along the major axis, the velocity ellipsoi d becomes tangential at the innermost bin, radial in the midrange radii, an d tangential again at the outermost bins. The rotation rises quickly at sma ll radii owing to the presence of the black hole. For the acceptable models , the radial-to-tangential [(sigma(theta)(2) + sigma(phi)(2))/2] dispersion in the midrange radii ranges over 1.1 < sigma(r)/sigma(t) < 1.7, with the smaller black holes requiring larger radial anisotropy. Compared with these three-integral models, two-integral isotropic models overestimate the blac k hole mass since they cannot provide adequate radial motion. However, the models presented in this paper still contain restrictive assumptions-namely , assumptions of constant M/L-v and spheroidal symmetry-requiring yet more models to study black hole properties in complete generality.