Relaxation and tidal stripping in rich clusters of galaxies. I. Evolution of the mass distribution

Journal Article · Sat Jan 01 04:00:00 EST 1983 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/160571· OSTI ID:6239757

Merritt, D

A set of differential equations is derived which describes the evolution of a rich cluster of galaxies over relaxation time scales. Two physical processes are included. Exchange of orbital kinetic energy between galaxies of different masses, due to gravitational two-body encounters, is computed from the isotropic, orbit-averaged Fokker-Planck equation. Tidal stripping of galaxies with massive halos is approximated by the corss sections of Richstone. The fraction of cluster mass in the ''background'' is allowed to increase with time as the galaxies are stripped; the energy of the background also increases due to dynamical interaction with the galaxies. The equations are integrated numerically, starting from a Schechter distribution of galaxy masses. Unless most of the virial mass in initially in the background, tidal stripping tends to obscure the effects of mass segregation (though not, presumably, luminosity segregation) by rapidly depleting the cluster core of massive galaxies. The background so produced dominates the core and is strongly concentrated to the center, falling off as r/sup -4/ at large radii. Putting most of the mass initially in the background increases the importance of mass segregation relative to stripping; in this case the galaxy distribution develops a significantly smaller core radius than the background. The final core mass distribution is qualitatively similar in both cases to that of a cD galaxy, in that it contains a central mass of low velocity dispersion surrounded by a high velocity dispersion envelope. However, the mass in the cluster core tends to decrease with time. Tidal strippings greatly increases dynamical friction time scales by reducing galaxy masses, and these results suggest that the small amounts of luminosity segregation observed in rich clusters might be consistent with all of the cluster mass having been originally tied to galaxies.

• Research Organization: National Radio Astronomy Observatory
• OSTI ID: 6239757
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 264:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DIFFERENTIAL EQUATIONS
EQUATIONS
FOKKER-PLANCK EQUATION
GALACTIC EVOLUTION
GALAXY CLUSTERS
LUMINOSITY
MASS
MATHEMATICAL MODELS
MORPHOLOGY
NUMERICAL SOLUTION
OPTICAL PROPERTIES
ORBITS
PARTIAL DIFFERENTIAL EQUATIONS
PHYSICAL PROPERTIES