STAR AND CLUSTER FORMATION IN NGC-1275

Imaging of the nuclear region of the central galaxy in the Perseus Cluster, NGC 1275, has confirmed the existence of luminous, blue, and unresolved objects surrounding the nucleus. A search of archival material indicates that none of these objects has varied significantly over the past 8 yr and that no new bright objects have either appeared or disappeared. This eliminates either ultraluminous stars or supernovae as explanations of these sources; young and luminous star clusters are the most probable interpretation. Analysis of the photometry of these clusters suggests that they have formed continuously at least over the past several hundred million years, making it unlikely that a galaxy-galaxy interaction triggered the star formation. However, an interaction with another galaxy, while not necessary to supply the gas for the cluster formation, may provide the perturbation necessary to get the star formation underway. A more realistic interpretation is that the process being observed is a result of the massive cooling flow known to exist around NGC 1275. Masses up to 10(7) M. are estimated for the most massive clusters, and at least 0.2% of the total mass deposited by the cooling flow is being formed into clusters. When the contribution from the background light from the galaxy is included, it appears that a large fraction of the cooling flow mass into the central 8 kpc of the galaxy is being converted into stars. From the current properties of these clusters, together with evolutionary models, we demonstrate that the NGC 1275 clusters are plausible precursors for systems resembling the globular clusters in the Milky Way Galaxy. A scenario is developed for star formation in a cooling flow in which gas clouds confined by weak magnetic fields are allowed to remain at low densities below approximately 10(4) K. The critical Jeans mass for such magnetically supported clouds is then approximately 10(6) M.. Cloud-Cloud collisions and coagulation in the high cloud density environment at the center of the galaxy then causes some clouds to become gravitationally unstable and to form globular clusters.