THE YOUNG STAR CLUSTER IN NGC 1275 - H-ALPHA LINEWIDTH AND STAR-FORMATION PROPERTIES

High spectral resolution observations of the massive young star cluster in the filaments of NGC 1275 reveal that the associated Hα emission line has a velocity width comparable to, or somewhat less than, that of Hα in typical giant H II regions of similar emission-line luminosity. If this linewidth reflects virial motions of matter within the star-forming region, as has been suggested for other giant H II regions, the mass fraction represented by massive, ionizing stars is not unusually small in this object, and may actually be somewhat larger than average. This behavior is contrary to scenarios of preferential low-mass star formation that have been invoked to reconcile x-ray and optical indications of mass accretion in this object and other cooling-flow galaxies. The observations also confirm that the cluster emission connects smoothly in projected location and velocity with emission from a low-ionization nebular filament. If this region is typical of star formation in cooling flows, it provides strong evidence that the mass accretion rate is less than that predicted from estimates based on x-ray cooling.