THE VELOCITY DISPERSION-TEMPERATURE CORRELATION FROM A LIMITED CLUSTER SAMPLE

Most studies of correlations between X-ray and optical properties of g alaxy clusters have used the largest samples of data available, regard less of the morphological types of clusters included. Given the increa sing evidence that morphology is related to a cluster's degree of dyna mical evolution, we approach the study of X-ray and optical correlatio ns differently. We evaluate the relationship between velocity dispersi on and temperature for a limited set of galaxy clusters taken from Bir d (1994) which all possess dominant central galaxies and which have be en explicitly corrected for the presence of substructure. We find that sigma, proportional to T-0.61+/-0.13. We use a Monte Carlo computer r outine to estimate the significance of this deviation from the sigma(r ) proportional to T-0.5 relationship predicted by the virial theorem. We find that the simulated correlation is steeper than the observed va lue only 4% of the time, which suggests that the deviation is signific ant. The combination of protogalactic winds and dynamical friction rep roduces nearly exactly the observed relationship between sigma(r) and T.