Relaxation and tidal stripping in rich clusters of galaxies. III. Growth of a massive central galaxy

Journal Article · Fri Feb 01 04:00:00 EST 1985 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/162860· OSTI ID:5862317

Merritt, D

The rate at which a massive galaxy (''cannibal'') grows by capturing other galaxies at the center of a rich, relaxed cluster is calculated. It is shown that the orbital decay preceding capture tends to leave the distribution of orbital velocities isotropic. As a result, most captures occur from nearly radial orbits, and relatively few from circular orbits. The capture rate is initially very low, due to the paucity of low-velocity galaxies, and to the fact that orbital decay times are comparable to a Hubble time. Encounters between galaxies further inhibit their orbital decay; this effect is important when the fraction of a cluster's mass that is bound to galaxies exceeds approx.15%. Assuming that less than approx.20% of a cluster's mass is attached to galaxies, and that the cluster velocity dispersion exceeds approx.500 km s/sup -1/, the typical rate of growth of a central galaxy by capture is rather small, amounting to somewhat less than 1 L* in a cluster lifetime. It is suggested (as in a previous paper) that most cD galaxies formed relatively rapidly, during the collapse and virialization of compact groups or poor clusters, and not during the quieter postcollapse stages as previous authors have advocated. The peculiar object V Zw 311 may be an example of a cD galaxy that is presently forming in this way. Subject headings: clustering-galaxies: evolution-galaxies: structure

• Research Organization: Department of Astronomy, University of California, Berkeley
• OSTI ID: 5862317
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 289:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANALYTICAL SOLUTION
DIFFERENTIAL EQUATIONS
EQUATIONS
EQUATIONS OF MOTION
GALACTIC EVOLUTION
GALAXIES
GALAXY CLUSTERS
MASS
MATHEMATICAL MODELS
MORPHOLOGY
ORBITS
PARTIAL DIFFERENTIAL EQUATIONS