Published in "The Evolution of Galaxies and Stellar Populations", eds. Beatrice M. Tinsley and Richard B. Larson, Yale University Observatory, 1977.


Alar Toomre

Massachusetts Institute of Technology

Abstract. As I hardly need to remind you, it has dawned rather widely in the last few years that the old notion of dynamical friction - tucked away in several 1943-vintage appendices to Chandrasekhar's (1942) book, and long appreciated mostly just by stellar dynamicists impressed by the rapid sinking of heavy masses in N-body simulations of star clusters - applies even to galaxies in a variety of settings. In his review, Ostriker has already stressed one such setting, the great clusters like Coma. Here I will focus on just the opposite extreme; some strange goings-on in mere pairs. Of course, neither of us would dispute that many modest groups and loose clusters of galaxies exist also, but for the moment it seems best to ignore them.

Table of Contents