The cosmic distance scale |
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| Authors: | Sidney van den Bergh |
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| Institution: | (1) Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, R.R. # 5, V8X 4M6 Victoria, B.C., Canada |
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| Abstract: | Summary The status of the cosmic distance scale problem in early 1989 is reviewed. Internally consistent distances to Local Group galaxies are given in Tables 5 and 6. Within the Local Group the distance scale is found to be 11±5% smaller than that previously adopted by Sandage and Tammann. Distances to nearby galaxies are used as stepping stones to the Virgo cluster. The interpretation of the Tully-Fisher observations of Virgo spirals is found to be ambiguous because it is not yet clear which spirals are cluster members and which are background objects. Distance estimates of the Virgo cluster obtained by different techniques are listed in Table 11. The distance modulus of the Virgo cluster is found to be 31.5±0.2, corresponding to a distance of 20±2 Mpc. The elliptical galaxies in the core of the Virgo cluster haveV
0=1200±46 kms–1, which corresponds toV
LG=1082±48 km s–1. With an infall velocity of 250±50 km s–1 this yields a cosmological redshiftV=1332±69 km s–1, from which a Hubble parameter H0=67±8 km s–1 Mpc–1 is obtained. Space Telescope observations of distant Cepheids, Tully-Fisher observations of spirals in the Hercules eluster, and interference filter observations of Virgo planetary nebulae in the light of OIII], should soon result in a major improvement in the accuracy with which H0 is known. |
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| Keywords: | clusters of galaxies: clusters globular: cosmology: galaxies Magellanic Clouds: stars variable |
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