Core Radii of Clusters of Galaxies at Different Redshifts
Abstract
Number counts of galaxies for five rich clusters of galaxies with redshifts ranging from z = 0.022 to z = 0.38 are fitted to isothermal gas-sphere models. A model with the same cutoff fits all five clusters. Core radii (= radius at which the surface number density equals one-half its peak value) are obtained for each of the clusters. At least three of the four smaller-redshift clusters have the same linear core radius to within a dispersion of 1 15 percent about an average value of (0.117 + 0.015) Mpc for H0 = 100km s ' Mpc-1. The most distant cluster (z = 0.38) has the same linear core radius if q0 to 1. The results are consistent with zero-pressure cosmological models having q0 = 1 1 1. Additional clusters must be studied in order to obtain better information regarding the intrinsic dispersion of core radii. Subject headings: celestial mechanics - cosmology - galaxies, clusters of
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1973
- DOI:
- 10.1086/151999
- Bibcode:
- 1973ApJ...180..699B