## 1. IntroductionIn recent years, evolution of galaxy clusters has attracted ever
more attention. On the one hand, it has become accessible for
observations, both with ground-based and space instruments. On the
other hand, discovery of Butcher-Oemler effect testifies to an epoch
of fast evolution in clusters, associated with galaxy interaction.
Mergers of galaxies
One of the effects associated with mergers is rapid evolution of the galaxy mass and angular momentum distribution function , related to appearance of massive galaxies. Calculation of is of great interest both by itself and in the context of a merger model of activity suggested by Kats & Kontorovich (1990, 1991). Given , one can predict the luminosity function of active galactic nuclei in this model. The mass function of merging galaxies
can be described in terms of the Smoluchowski
kinetic equation. As Cavaliere et al. (1991, 1992) and,
independently, Kontorovich et al. (1992), Kats et al. (1992) have shown, mergers result in an analog of phase transition (or
"explosive evolution"), which implies fast formation of a distribution
tail (corresponding to massive galaxies) and a "new phase":
cD-galaxies
The joint distribution function which takes into consideration both mass and angular momentum can be described by a generalized Smoluchowski equation (see Kats & Kontorovich 1990, 1992, where this equation was solved in the simplest case of a constant merger probability - an analog of phase transition does not take place in this variant - and without allowance for the orbital angular momentum). In this paper we present the results of simulation of galaxy mass and momentum evolution in clusters, with the orbital momentum and more realistic mass dependence of the merger probability taken into account. In Sect. 2 we discuss Monte Carlo simulation of mergers. In Sect. 3 we compare the results for with a direct numerical solution of the Smoluchowski equation. Sect. 4 contains discussion of the results. © European Southern Observatory (ESO) 1997 Online publication: April 6, 1998 |