The surface brightness fluctuations and globular cluster populations of Virgo elliptical and lenticular galaxies

The Virgo cluster of galaxies is a complex system composed of several sub-clusters or “clouds.” Although the relative positions of clouds can be determined by the low precision measurement of many galaxies in each cloud, the internal structure of individual clouds requires more precise measurement. The literature provides a few such measurements, but the number of galaxies with distances known to high precision remains small. In this study, the Hubble Space Telescope archive provides the data necessary for such measurements of 15 elliptical and lenticular galaxies using the fluctuations in the galaxies surface brightness (SBF) caused by the statistical variations in the density of stars in the target galaxy. Most of the sample galaxies are members of the largest of the Virgo clouds, that centered on M87. The M87 cloud appears significantly elongated along the line of sight, with members to the West of M87 placed generally further than those to the East. Distances to the few galaxies of other clouds agree well with cloud distances found in the literature.; Globular clusters (GC's) detected in these images provide a second (lower precision) means of distance determination. If both the SBF distances are correct and the peak magnitude of the GC luminosity function (GCLF) is nearly the same in all galaxies, the measured peak of GCLF should be proportional to the SBF distance modulus. These data indicate that this is the case. The color distributions of GC's, however, indicate that the GC populations have complex histories which vary significantly from galaxy to galaxy. Galaxies with large numbers of detected clusters show two distinct cluster populations with mean V – I colors near 1.01 and 1.26, the relative strength of which varies from galaxy to galaxy. The most dramatic example of this is M86, which shows only a single sharp peak near V – I = 1.03.