Virial properties of groups of galaxies.
Abstract
Modern techniques and data are used to derive virial parameters for numerous wellknown groups of galaxies. Virial masstolight ratios are typically 40120 solar units. The groups are gravitationally bound because (a) their crossing times are smaller than a Hubble time, and (b) the composite frequency distribution of their radial velocities is 'approximately' Gaussian. A correlation is observed between the virial masstolight ratio and the virial velocity dispersion. Contributions to this correlation by projection and quasiequilibrium effects, radial velocity uncertainties, and uncertainties in galactic mass are evaluated and found to be too small to explain the correlation. The average surface density of galaxies in groups appears to be independent of distance from the center out to a mean limiting radius.
 Publication:

The Astrophysical Journal
 Pub Date:
 September 1978
 DOI:
 10.1086/156422
 Bibcode:
 1978ApJ...224..724R
 Keywords:

 Galactic Clusters;
 Virial Theorem;
 Astronomical Catalogs;
 Galactic Evolution;
 Galactic Mass;
 Galactic Structure;
 Gravitational Effects;
 Luminosity;
 Mass Ratios;
 Radial Velocity;
 Tables (Data);
 Astrophysics;
 Groups of Galaxies:MasstoLight Ratios;
 Groups of Galaxies:Virial Theorem