LIMITS ON THE HUBBLE CONSTANT FROM THE HST DISTANCE OF M100

Because M100 is in the Virgo cluster, our recent measurement of its di stance has an impact on the calibration of all of the extragalactic se condary distance indicators which reach beyond Virgo and define the ex pansion rate. We examine the consequences of a 17 Mpc M100 distance, q uestioning its consistency with supernova and other distances. The dis tance of M100 provides two separate constraints on the Hubble constant . First, it verifies the emissivity calculations for Type II supernova e. These models, fitted to SN 1987A, have recently been used to measur e host galaxy distances beyond 10(4) km s-l recession velocity. Second , it constrains the distance of the Virgo cluster, which in spite of i ts apparent complex structure, provides an effective calibration for a set of reliable and well-used secondary distance indicators. Reviewin g the Type II supernova distances for three galaxies with Cepheid dist ances, 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 (co smological redshift) of the Virgo cluster, we find H-0 = 81 +/- 11 km s(-1) Mpc(-1), plus an additional uncertainty arising from the extende d nature of the Virgo cluster. Employing the Virgo cluster as calibrat or, we obtain measurements of the Hubble constant from extant surface brightness fluctuation measurements, elliptical galaxy velocity disper sion measurements, the Tully-Fisher relation, and the Type Ia supernov a 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 consist ent, 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 st ructure of the Virgo cluster; these support the recent conclusion of F reedman and coworkers that the appropriate uncertainty to attach to th e Hubble constant from the Cepheid distance to Virgo is 20%. A value o f H-0 = 80 +/- 17 km s(-1) Mpc(-1) is consistent with all the data dis cussed 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 bet ween the distance indicators investigated here and constrain the Hubbl e constant to 10% accuracy.