LIMITS ON THE HUBBLE CONSTANT FROM THE HST DISTANCE OF M100

Because M100 is in the Virgo cluster, our recent measurement of its distance has an impact on the calibration of all of the extragalactic secondary distance indicators which reach beyond Virgo and define the expansion rate. We examine the consequences of a 17 Mpc M100 distance, questioning its consistency with supernova and other distances. The distance of M100 provides two separate constraints on the Hubble constant. First, it verifies the emissivity calculations for Type II supernovae. These models, fitted to SN 1987A, have recently been used to measure host galaxy distances beyond 10(4) km s-l recession velocity. Second, it constrains the distance of the Virgo cluster, which in spite of its apparent complex structure, provides an effective calibration for a set of reliable and well-used secondary distance indicators. Reviewing the Type II supernova distances for three galaxies with Cepheid distances, we find consistency, which supports the recent SN result H-0 = 73 +/- 11 km s(-1) Mpc(-1). This support is independent of where M100 lies in the Virgo cluster. Reviewing the Hubble recession velocity (cosmological redshift) of the Virgo cluster, we find H-0 = 81 +/- 11 km s(-1) Mpc(-1), plus an additional uncertainty arising from the extended nature of the Virgo cluster. Employing the Virgo cluster as calibrator, we obtain measurements of the Hubble constant from extant surface brightness fluctuation measurements, elliptical galaxy velocity dispersion measurements, the Tully-Fisher relation, and the Type Ia supernova standard candle. These yield H-0 = 84 +/- 16, 76 +/- 10, 82 +/- 11, and 71 +/- 10 km s(-1) Mpc(-1), respectively. All of these are consistent, but they are all subject to the additional uncertainty from Virgo's line-of-sight depth. We explore a number of simple models of the structure of the Virgo cluster; these support the recent conclusion of Freedman and coworkers that the appropriate uncertainty to attach to the Hubble constant from the Cepheid distance to Virgo is 20%. A value of H-0 = 80 +/- 17 km s(-1) Mpc(-1) is consistent with all the data discussed herein. Confidence limits with 95% significance can be assigned to the interval 50 < H-0 < 100 km s(-1) Mpc(-1). Further work in this program should be expected to identify the systematic differences between the distance indicators investigated here and constrain the Hubble constant to 10% accuracy.