The fate of dense stellar systems

The fates of dense star clusters containing approximately 108 stars are investigated. If such systems have evolved to the stage when disruptive stellar collisions are important, the collisionally liberated gaseous debris may settle towards the centre. It has been suggested that this gas condenses into a population of 'new' main sequence stars. Such a stellar subsystem commences an autonomous contraction, at a rate controlled by collisions among the 'new' stars themselves, when it attains a fraction epsilon = (ellipticity of original cluster)sup(1/2) of the total cluster mass. The gas liberated by stellar collisions can no longer recondense into stars when the concomitant luminosity rises to the Eddington limit for the subsystem: at this stage the subsystem must dissolve into an amorphous gas cloud. Possible evolutionary tracks are discussed for the massive object thus formed. Dense star clusters may be responsible for some of the low-level manifestations of activity in galactic nuclei; but they are probably merely precursor stages of the more spectacular quasar-type phenomena, which develop after a massive object has formed. (author)