Binary model for the coma cluster of galaxies

Journal Article · Fri Jun 15 04:00:00 EDT 1979 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/157124· OSTI ID:6130926

Valtonen, M J; Byrd, G G

We study the dynamics of galaxies in the Coma cluster and find that the cluster is probably dominated by a central binary of galaxies NGC 4874--NGC4889. We estimate their total mass to be about 3 x 10/sup 14/ M/sub sun/ by two independent methods (assuming in Hubble constant of 100 km s/sup -1/ Mpc/sup -1/). This binary is efficient in dynamically ejecting smaller galaxies, some of of which are seen in projection against the inner 3/sup 0/ radius of the cluster and which, if erroneously considered as bound members, cause a serious overestimate of the mass of the entire cluster. Taking account of the ejected galaxies, we estimate the total cluster mass to be 4--9 x 10/sup 14/ M/sub sun/, with a corresponding mass-to-light ratio for a typical galaxy in the range of 20--120 solar units. The origin of the secondary maximum observed in the radial surface density profile is studied. We consider it to be a remnant of a shell of galaxies which formed around the central binary. This shell expanded, then collapsed into the binary, and is now reexpanding. This is supported by the coincidence of the minimum in the cluster eccentricity and radical velocity dispersion at the same radial distance as the secondary maximum. Numerical simulations of a cluster model with a massive central binary and a spherical shell of test particles are performed, and they reproduce the observed shape, galaxy density, and radial velocity distributions in the Coma cluster fairly well. Consequences of extending the model to other clusters are discussed.

• Research Organization: Department of Physics and Astronomy, University of Alabama
• OSTI ID: 6130926
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 230:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RADIO SOURCES
DISTRIBUTION
GALAXIES
GALAXY CLUSTERS
MASS
RADIAL VELOCITY
RADIO GALAXIES
SPATIAL DISTRIBUTION
VELOCITY
VIRIAL THEOREM