Anisotropic velocity dispersions in spherical galaxies

Under the assumptions that while mass-to-luminosity ratio is fixed, the velocity dispersion may be anisotropic, the velocity dispersion profiles of elliptical galaxies reported in the literature can all be fitted. Velocity dispersion profiles are integrated over apertures, and it is noted that M/L ratios computed by Poveda's (1958) method, and a central value for the velocity dispersion, are extremely uncertain. Slight anisotropy leads to errors of 40%, and models yielding much larger errors are possible. Central velocity dispersions measured through typical apertures vary less than 5% with aperture size for the case of a galaxy that is brighter than 14 mag. Little deviation from the Gaussian is found in calculations of spectral line profiles that would be observed through typical apertures.