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[99.05] STIS Observations of Nearby Ellipticals: Models of Stellar Orbits and Black Hole Masses

K. Gebhardt (UCSC/Lick Observatory), J. Pinkney, D. Richstone (University of Michigan)

The mass of a central black hole in a galaxy provides significant information concerning the evolution of the stellar system. We are involved in a program to determine these black-hole masses to high accuracy in nearby early-type galaxies using HST and ground-based spectroscopy. Pinkney et al. present the kinematic results for the present sample. We use a fully-general modeling program to estimate the mass without assuming a form for the stellar orbital distribution, and, hence, provide the current orbital structure of the stars near the center as well. We present the results for three galaxies, NGC821, NGC4473, and NGC4697. In both NGC821 and NGC4473, the data require a central massive black hole; models for NGC4697 are in progress. The measured stellar orbital distributions are characteristic of other galaxies studied with these general models, suggesting a common history amongst galaxies. We use the measured orbital structure to determine the dominant evolutionary processes that effect both the black-hole mass and the global galaxy structure. It appears that elliptical galaxy formation and evolution is intimately connected to the existence of a central massive black hole.