1995A&A...299...25T

We continue the analysis of star formation in a galactic nucleus by modeling the dynamical evolution of the nuclear gas: Initially, a massive gas cloud of 10⁸M_☉ and 200pc diameter sits in the extended stellar cluster of the nuclear bulge. The gas is supported against collapse by turbulent motions. As the turbulent energy is dissipated the cloud radius shrinks. Above some critical gas density, star formation occurs and the subsequent supernova explosions of type II can replenish the turbulent energy. Besides the loss of gas through star formation, there is a constant supply of fresh gas from outside the nucleus. In a previous paper we discussed repetitive bursts of star formation. Here we extend the discussion to four other possible scenarios: a) catastrophic collapse of the gas towards a very dense and massive stellar cluster with the subsequent formation of a supermassive star collapsing finally into a supermassive black hole, b) repetitive expulsions of the gas from the nucleus, c) quasi-stationarity, and d) violent mass influx into the nucleus initiated by collision with another galaxy. We present calculations for the four new scenarios under realistic assumptions of the basic parameters of a galactic nucleus. Because of the simplicity of our model, it cannot precisely limit the range of the parameters of a galactic nucleus under which a particular kind of solution is realized, but only show their order of magnitude. The simplicity has, on the other hand, the advantage that the numerical results can easily be understood and interpreted in a semi-quantitative way.