Extragalactic globular clusters. III - Metallicity comparisons and anomalies

Abstract

A method based on the strengths of six absorption line indices measured in integrated spectra is used to derive metallicities for 22 globular clusters associated with the Sc galaxy, M33, 10 globular clusters with the giant elliptical galaxy, M87, eight globular clusters associated with the Sb(r)I-II galaxy, M81, and three globular clusters associated with the Fornax dwarf elliptical galaxy. Mean metallicities are derived for 38 bright galaxies, mostly ellipticals, 29 dwarf elliptical galaxies in the Virgo cluster, 10 dwarf elliptical galaxies in the Fornax cluster, and four local group dwarf galaxies. These results are compared with previously derived metallicities for 149 clusters in M31 and with the Milky Way cluster metallicities to show that the mean metallicity of a cluster system is linearly related to the luminosity of the parent galaxy. A similar relationship is suggested between galaxy metallicity and luminosity for the bright and dwarf galaxies.