Focussing in on H_0

Abstract

Six independent methods yield a Virgo cluster modulus of (m-M)=31.66+/- 0.08. This inserted into the Hubble diagram of clusters, whose relative distances to the Virgo cluster are known, gives H_0=54+/-4. The result is independent of any observed or inferred velocity of the Virgo cluster and holds out 10 000 km/s. An analogous use of the Fornax cluster is not yet possible because of its unknown structure in space and its poorly understood distance relative to other clusters. Field galaxies, corrected for Malmquist bias, give H_0=53+/-3. The results of purely physical distance determinations cluster around H_0=55+/-10. These results may be compared with the high-weight determination of H_0=58.5+/-3 from Cepheid-calibrated SNe Ia and their Hubble diagram out to 30 000 km/s (Saha 1996). The agreement of the independent methods suggests that the external error of an adopted value of H_0=58 is equal or less than 13%.