in Mass-Transfer Induced Activity in Galaxies, ed. I. Shlosman (Cambridge University Press, Cambridge), 1-22 (1994)

Mass-Transfer Induced Activity in Galaxies: an Introduction

E.S. Phinney

Theoretical Astrophysics, 130-33 California Institute of Technology, Pasadena, California 91125

Galaxies with elevated metabolic rates get energy from their gaseous food by extracting its nuclear energy (in stars), and its gravitational energy (via accretion onto massive black holes). There is strong evidence that interactions with other galaxies trigger star formation activity, and weaker evidence that it triggers black hole accretion (nuclear activity). We review the processes by which interactions can remove angular momentum from gas, particularly gravitational torques and the m=2, m=1, Jeans and fission instabilities that give rise to them. There is ample evidence, both theoretical and observational, that these can remove enough angular momentum to move much of a galaxy's gas from ~3kpc to ~300pc. This is still many decades from the ~10^{-5} pc scales of stars and black hole horizons. We discuss star formation, the interpretation of simulations, and cosmological implications. The evolution of binary supermassive black holes, and the problem of forming a dense (< 1 pc) nuclear star cluster are examined.

1 What is Mass-Transfer Induced Activity in Galaxies?

2 Induced Activity in Galaxies

2.1 Observations favoring induced activity
2.2 Observations Conflicting (?) with Induced Activity
2.3 The Canonical Theoretical Model of Induced Activity

3 Models of the First Stage of Mass Transfer ( ~3kpc to ~300pc)

3.1 The Significance of Resonances
3.2 Bars from Stars
3.3 `Bars' from Black Holes
3.4 Instabilities with m=1

4 Behavior of Gas

5 Star Formation

5.1 Nuclear (< 10 pc) Star Formation

6 Concluding Remarks