The Luminosity Function of Globular Clusters as an Extragalactic Distance Indicator

Abstract

The absolute magnitude M* of the peak of the globular cluster luminosity function (GCLF), approximated by a Gaussian, can be calibrated independently in the Galaxy and M 31 through RR Lyr stars and Cepheids, respectively. They yield, in perfect agreement, M*_B = -6.93+-0.08 and M*_V = -7.62+-0.08. Application of these values to the GCLFs in the Leo Group (n=2), the Virgo cluster (n=8), and the Coma cluster (n=2) gives distances which agree with the best determinations from other methods. However, the corresponding distance of the Fornax cluster (n=7) is significantly underestimated, and the distances of several field galaxies are inconsistent. A second parameter, like the width of the GCLF or the color of the peak, is apparently needed to control differences in the GC formation history.