The Extragalactic Distance Scale
Abstract
Cepheid variables are used to derive a Virgo cluster distance of 16.0 +/ 1.5 Mpc. In conjunction with the mean Coma radial velocity and the wellestablished Coma/Virgo distance ratio, this yields a Hubble parameter H_0 = 81 +/ 8 km s^1 Mpc^1. By combining this value with an age of the Universe >~ 16.8 +/ 2.1 Gyr, that is derived from the metalpoor globular cluster M92, one obtains f (Omega, Lambda) >~ 1.39 +/ 0.22. This value is only marginally consistent with an Einsteinde Sitter universe with Omega = 0 and Lambda = 0, which has f =1. An Einsteinde Sitter universe with Omega = 1 and Lambda = 0, for which f = 2/3, appears to be excluded at the 3sigma level. It is shown that some recent small values of H_0 may have resulted from the large intrinsic dispersion in the linear diameters of galaxies, and from the fact that wellobserved supernovae of Type Ia exhibit a luminosity range of ~20 at maximum light. A representative sample of recent estimates of H_0 is given in Table 1. The median value of the Hubble parameter from the data in this table is H_0 = 72 km s^1 Mpc ^1 from which f(Omega,Lambda) >~ 1.24. (SECTION: A Debate on The Scale of the Universe)
 Publication:

Publications of the Astronomical Society of the Pacific
 Pub Date:
 December 1996
 DOI:
 10.1086/133839
 arXiv:
 arXiv:astroph/9604070
 Bibcode:
 1996PASP..108.1091V
 Keywords:

 Astrophysics
 EPrint:
 22 pages, Postscript, no figures. Also available at: http://www.dao.nrc.ca/DAO/SCIENCE