The correlation between X-ray luminosity and velicity dispersion in clusters of galaxies.

The X-ray luminosity-velocity dispersion correlation for 42 clusters is analyzed for which velocity dispersion and either HEAO-1 A-2 fluxes and/or Einstein luminosities are available. The relations between X-ray luminosity, velocity dispersion, and central surface density expected for a thermal bremsstrahllung model are generalized by relaxing some of the mathematical and physical constraints. It is found that there is a strong correlation between X-ray luminosity and velocity dispersion that agrees well with the one expected if the X-rays come from a hot isothermal gas bound to the clusters. Since a correlation is predicted between the central surface density and the X-ray luminosity of clusters, a strong correlation is also expected between the morphological-type populations in the central regions and the velocity dispersions.