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The measurement of the distance of M100 reported at this meeting by the HST Key Project Team provides two separate constraints on the Hubble Constant. First, it verifies the emissivity calculations for type II supernovae. These models, fitted to SN1987A, have recently been used to measure host galaxy distances beyond 10$^4$ km/s 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 between the two, which supports recent measurements of H$_0$ using the Expanding Photospheres Method. This support is independent of where M100 lies in 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 consistent values of the Hubble Constant, but they are all subject to the additional uncertainty from Virgo's line-of-sight depth.
Our presentation explores a number of simple models of the structure of the Virgo cluster; these support the recent conclusion presented by Freedman at this meeting that the appropriate uncertainty to attach to the Hubble Constant from the Cepheid distance to Virgo is 20\%. Confidence limits with 95\% significance can be assigned to the interval 50 $<$ H$_0$ $<$ 100 km/sec/Mpc.
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