STAR-FORMATION IN GALACTIC NUCLEI

We analyze the evolution of a massive gas cloud of order 10(8)M. in th e nucleus of a galaxy. The gas is located in the potential well of the central stellar cluster and is supported against free fall by turbule nt motions. As the turbulent energy dissipates via cloud-cloud collisi ons the radius of the gas cloud shrinks and at a critical density star s begin to form. Subsequent supernova explosions are then an important source of turbulent energy of the cloud. If the initial mass function for star formation is top-heavy with a lower limit m1 greater-than-or -equal-to 1M. then the pumping rate of turbulent energy from SN exceed s the dissipation rate of the gas and repetitive bursts of star format ion occur for a wide range of the basic parameters. We discuss this ca se in detail and conclude that if nuclear activity is defined by a lar ge luminosity (greater-than-or-equal-to 10(10)L.) from a small volume (R less-than-or-equal-to 1 kpc) activity it is an intrinsic process an d need not be triggered from outside. The role of an interacting galax y, which is frequently observed, is limited to the supply of fresh gas . In addition, we find under special conditions other types of solutio n to be discussed in a subsequent paper.