Galaxy Morphological Segregation in Clusters: Local versus Global Conditions

We study the relative fraction of galaxy morphological types in clusters, asa function of the projected local galaxy density and different globalparameters: cluster projected gas density, cluster projected total mass density, and reduced clustercentric distance. Since local and global densities arecorrelated, we have considered different tests to search for the parameters towhich segregation show the strongest dependence. Also, we have explored theresults of our analysis applied to the central regions of the clusters andtheir outskirts. We consider a sample of clusters of galaxies with temperatureestimates to derive the projected mass density profile and the 500 densitycontrast radius ($r_{500}$) using the NFW model and the scaling relationrespectively. The X-ray surface brightness profiles are used to obtain theprojected gas density assuming the hydrostatic equilibrium model. Our resultssuggest that the morphological segregation in clusters is controlled by thelocal galaxy density in the outskirts. On the other hand, the global projectedmass density, shows the strongest correlation with the fraction ofmorphological types in the central high density region, with a marginaldependence on the local galaxy density.Comment: 10 pages, 8 figures, Accepted AJ (February 2001 issue