Observations of the internal dynamics of 12 elliptical galaxies

Abstract

Long slit SIT spectra for 12 elliptical galaxies, obtained with the Hale 5 m reflector, have been measured using a Fourier quotient technique to yield rotation curves, velocity dispersion profiles, and line strength profiles down to a fraction of the night sky. We confirm Illingworth's conclusion that ellipticals exhibit far less rotation along their major axes than is predicted by isotropic oblate models. They also fall short of Binney's predictions for isotropic prolate models. Not one of nine galaxies shows rotation along its minor axis greater than 15% of its central dispersion. NGC 596, a galaxy in which the position angle of the major axis changes dramatically, rotates fairly rapidly in its nearly spherical core. Galaxies of the same ellipticity exhibit substantially different amounts of rotation. Making use of the mean relation between absolute magnitude and central velocity dispersion, we find remarkably small scatter in the core mass-to-light ratios of the ellipticals studied by King and no dependence of this ratio on absolute magnitude.