THE EXTRAGALACTIC DISTANCE SCALE

Authors
Citation
S. Vandenbergh, THE EXTRAGALACTIC DISTANCE SCALE, Publications of the Astronomical Society of the Pacific, 108(730), 1996, pp. 1091-1096
Citations number
78
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Astronomy & Astrophysics
Journal title
Publications of the Astronomical Society of the Pacific
ISSN journal
0004-6280 → ACNP
Volume
108
Issue
730
Year of publication
1996
Pages
1091 - 1096
Database
ISI
SICI code
0004-6280(1996)108:730<1091:TEDS>2.0.ZU;2-X
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 w ell-established Coma/Virgo distance ratio, this yields a Hubble parame ter H-0=81+/-8 km s(-1) Mpc(-1). By combining this value with an age o f the Universe greater than or similar to 16.8+/-2.1 Gyr that is deriv ed from the metal-poor globular cluster M92, one obtains f(Omega,Lambd a)greater than or similar to 1.39+/-0.22. This value is only marginall y consistent with an Einstein-de Sitter universe with Omega=0 and Lamb da=0, which has f=1. An Einstein-de Sitter universe with Omega=1 and L ambda=0, for which f=2/3, appears to be excluded at the 3 sigma level. It is shown that some recent small values of H-0 may have resulted fr om the large intrinsic dispersion in the linear diameters of galaxies, and from the fact that well-observed supernovae of Type Ia exhibit a luminosity range of similar to 20 at maximum light. A representative s ample 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)greater than or similar to 1.24 .