Dynamics of rich clusters of galaxies. I. The Coma cluster

Journal Article · Thu Jul 01 04:00:00 EDT 1982 · Astron. J.; (United States)

DOI:https://doi.org/10.1086/113178· OSTI ID:5201755

Kent, S M; Gunn, J E

The structure and dynamics of the Coma cluster are analyzed using self-consistent equilibrium dynamical models. Observational material for Coma is culled from a variety of sources. Projected surface, density, and velocity-dispersion profiles are derived extending out to a radius of 3/sup 0/ from the cluster center, which are essentially free from field contamination. Segregation of galaxies by luminosity and morphology are discussed and a quantitative estimate of the latter is made. The method of constructing self-consistent dynamical models is discussed. Four different forms of the distribution function are analyzed allowing for different possible dependences of f on energy and angular momentum. Properties of typical models that might resemble actual clusters are presented, and the importance of having velocity-dispersion information is empha sized. The effect of a central massive object such as a cD galaxy on the core structure is illustrated. A comparison of these models with Coma reveals that only models with a distribution function in which the ratio of tangential to radial velocity dispersions is everywhere constant give acceptable fits. In particular, it is possible to rule out models that have isotropic motions in the core and predominantly radial motions in the halo. For H/sub 0/ = 50, the best-fitting models give a total projected mass inside 3/sup 0/ of 2.9 x 10/sup 15/ M/sub sun/ , a core radius of 340--400 kpc (8.5'--10'), an upper limit to any central massive object of approx.10/sup 13/ M/sub sun/ , and a mass-to-blue-light ratio of M/L = 181. From cosmological considerations the cluster ''edge'' is determined to lie at rapprox.5/sup 0/--6/sup 0/. The possible distribution of ''dark matter'' in Coma is discussed and it is argued that this distribution cannot be significantly different from that of the galaxies. The dynamics of morphological segregation are examined quantitatively, and are explained at least qualitatively.

• Research Organization: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138
• OSTI ID: 5201755
• Journal Information: Astron. J.; (United States), Journal Name: Astron. J.; (United States) Vol. 87:7; ISSN ANJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DISTRIBUTION FUNCTIONS
DYNAMICS
ELECTROMAGNETIC RADIATION
FUNCTIONS
GALAXY CLUSTERS
IONIZING RADIATIONS
LUMINOSITY
MECHANICS
MORPHOLOGY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIAL VELOCITY
RADIATIONS
VELOCITY
X RADIATION