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.

13 pages, 10 tables, LaTeX (paspconf.sty + natbib.sty). Contribution to the proceedings of the Colloquium "Harmonizing Cosmic Distance Scales in a Post-Hipparcos Era", Haguenau, France, 14-16 Sep.98, ASP Conf. Series, eds. D. Egret & A. Heck