KINEMATICAL TESTS FOR THE INTRINSIC SHAPES OF GALAXIES

Determining the intrinsic shape of elliptical galaxies has been an illusive enterprise, but one fundamental to the understanding of their internal dynamics and formation. We approach the problem dynamically; noting that the velocity dispersion is largest when sighted down the longest axis, we derive the correlations of velocity dispersion with observed eccentricity expected, after the known trend of velocity dispersion with luminosity is removed. Using a compilation of published data, we determine more accurately the relation between luminosity and velocity dispersion. The residuals are examined as a function of axis ratio in order to construct a test for the intrinsic shape of galaxies. The effects of projection are modelled and possible intrinsic variations are examined. Model catalogues, generated from the theory by a Monte Carlo technique, are compared to the observational data. This test is inconclusive, since it excludes only one of the four proposed configurations, but we discuss further probes which are capable of untangling intrinsic variations from those of projection. © 1984 Royal Astronomical Society.