Surface brightness fluctuations and the distance to the Virgo Cluster

We present observations and a surface brightness fluctuation analysis of M32, NGC 3379, and five Virgo Cluster galaxies which yield the typical brightness of giant stars, m^bar^, in these galaxies. We find that the apparent magnitude m^bar^ in the R band is 24.4 in M32, 30.2 in NGC 3379, and 31.0 in Virgo. The "color" of this average flux from giant stars is V-I = 2.2 in all these systems with a slight decrease in m^bar^ for bluer galaxies. Assuming a distance of 0.72 Mpc for M32 and correcting for the color effect in m^bar^ we derive distances of 9 Mpc for NGC 3379 and 14 Mpc for Virgo, accurate to about 10%. From this we find a Hubble constant of 88 km s^-1^ Mpc^-1^; the principal error now comes from the uncertainties in the Hubble flow velocity of the Virgo Cluster. The existing data are precise enough to resolve front to back distances in Virgo; we believe that NGC 4472 is 2 Mpc more distant than the rest of the galaxies near M87. It is apparent from these data that this method can be used to measure m^bar^ in galaxies at least 40-50 Mpc distant.