N-body simulations of stellar systems containing massive black holes

Claims that recent observations of the elliptical galaxy M87 are consistent with the presence of a central black hole of approx. 5 x 109M/sub sun/ (Young et al. 1978, Sargent et al. 1978, de Vaucouleurs and Nieto 1979), motivate an examination of the stellar dynamics of spherical, collisionless systems with and without massive central black holes. Three lines of investigation are described. (1) A spherical, collisionless N-body code was developed in order to study the cosmological infall models of galaxy formation initially proposed by Gott (1975). The simulations show that models in which primordial black holes act as a seed for galaxy formation produce projected velocity dispersion profiles which are much steeper than those observed in M87 or other ellipticals. (2) Models are discussed in which an initially very small black hole grow adiabatically in an isothermal core by consuming infalling material from outside the core. Such models probably have more physical significance than results used by others, which are based on collisionally relaxed systems. (3) A simple dynamical model for spherical, collisionless systems is presented in which the velocity distribution is anisotropic. Using an anisotropic distribution function proposed by Ogorodnikov (1966), the first moment of the corresponding Boltzmann equation is integrated to give the resulting density and velocity dispersion profiles. These distributions plus a central point source of light give a good fit to the data from recent observations of M87 wihout requiring a supermassive central object