Discovery of a massive, young star cluster in the filaments of NGC 1275

Optical and near-UV spectroscopy of an emission-line filament in the low-velocity system of NGC 1275 has revealed the presence of a young star-forming region, as evidenced by a very blue continuum source coincident with line emission characteristic of H II regions. This is the first direct detection of star formation in gas thought to be part of a cooling flow. If this young cluster is representative of star formation in cooling-flow galaxies, the current initial mass function (IMF) for these objects is not truncated at a level that excludes the formation of massive stars. For a Salpeter IMF, the cluster contains a mass similar to the largest globular clusters associated with the Milky Way (about 5 x 10 to the 6th solar masses). A dynamical constraint on the total mass of the stellar cluster may be available through measurement of its emission-line widths. It is suggested that the A-star continuum characterizing the near-nuclear population of NGC 1275 is better explained as the signature of a fading starburst, rather than as star formation in a cooling flow. 27 refs