THE HUBBLE FLOW FROM BRIGHTEST CLUSTER GALAXIES

We have imaged 114 Brightest Cluster Galaxies (BCG) from a full-sky sample of all Abell clusters within 15,000 km s-1. We present a BCG distance indicator based on reexamination of the Hoessel relationship between BCG metric luminosity and structure. The BCG Hubble diagram is consistent with a uniform Hubble flow over 0.01 less-than-or-equal-to z less-than-or-equal-to 0.05. We limit any variation in the apparent H-0 (measured globally from our location) to DELTAH-0/H-0 < 0.07 across the same volume. We use the Virgo BCG, NGC 4472, to calibrate the BCG Hubble diagram directly, independent of the Virgocentric infall pattern. For the observed distance to NGC 4472 of 14.4 Mpc, H-0 = 77 + 8 km s-1 Mpc-1. Alternatively, if NGC 4472 is at the Sandage & Tammann 21.9 Mpc distance to Virgo, then H-0 = 51 +/- 5. The BCG Hubble constant on either the short or long system is consistent with Hubble constants measured on the same system within the local supercluster. Plausible high values of H-0 observed within the local supercluster therefore cannot be explained as biased measures of the true H-0 due to velocity anomalies induced by large-scale structure.