Galaxy Correlations as a Function of Morphological Type

Abstract

Using the Uppsala Catalog, which is complete to Mpg = 14.5, we have determined the two- point angular correlation functions for the distributions of galaxies of various morphological types. Within the limited statistics of the sample, all the measured correlation functions can be fitted to power laws in angular separation. We find that elliptical-elliptical galaxy clustering may be characterized by a power law with a slope steeper than that appropriate for spiral-spiral clustering. The lenticular-lenticular slope is intermediate. Analysis of the sample with the rich clusters Virgo and Coma deleted gives a very similar set of correlation functions. Using the derived correlation functions, we present expressions for the mean number of galaxies of a given type in excess of random within a sphere of a given radius centered on a random galaxy of specified morphological type. The number of galaxies of any type within a megaparsec of a random elliptical is about twice the number within the same distance of a random spiral. Our results indicate that differences in galactic morphology are unlikely to be due solely to environmental interactions which take place long after the era of galaxy formation. Differences in the correlation functions also have a small effect on the determination of binary galaxy masses. Subject headings: galaxies: clusters of - galaxies: general