A PRELIMINARY CLASSIFICATION OF THE FORMS OF GALAXIES ACCORDING TO THEIR STELLAR POPULATION

Abstract

A recent paper has given an outline of a revised system of classification of the forms of galaxies, together with types for 608 systems. That investigation will be designated Paper I, and the present one Paper II. The galaxies classified on the revised Yerkes system in Paper I include a large fraction of the northern entries in the ShapleyAmes Catalogue. It seemed advisable to make the classification approximately complete to some limiting apparent magnitude ; a program was therefore devised to classify a number of additional galaxies. Through the kindness of Dr. I. S. Bowen and the Committee of the Mount Wilson and Palomar Observatories, I was permitted to make use of the original negatives of the National Geographic Society-Palomar Observatory Sky Survey for the purpose. The present paper completes the classification of all galaxies brighter than magnitude 13.1 in the Shapley-Ames Catalogue and north of O = —25°, with two exceptions : the object NGC 2149 has been omitted from the catalogue, since it appears to be a diffuse nebulosity, rather than a galaxy; NGC 2798 was omitted inadvertently. The galaxies included in the present paper were classified on the 48-inch Sky Survey plates during a period as guest investigator at Pasadena in the autumn of 1958. A large number of galaxies in Paper I were reclassified without knowledge as to the earlier type assigned ; this overlap furnishes material for an accurate determination of the systematic characteristics of the two series. ii