Planetary Camera observations of NGC 1275 - Discovery of a central population of compact massive blue star clusters

• Published in: The Astronomical journal 1992-03, Vol.103 (3), p.691-702
• Main Authors: Holtzman, Jon A., Faber, S. M., Shaya, Edward J., Lauer, Tod R., Groth, Edward J., Hunter, Deidre A., Baum, William A., Ewald, S. P., Hester, J. J., Light, Robert M.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; Earth, ocean, space; Exact sciences and technology; Quasars. Active or peculiar galaxies, objects, and systems; Stellar systems. Galactic and extragalactic objects and systems. The universe
• ISSN: 0004-6256; 1538-3881
• DOI: 10.1086/116094

The discovery of a population of bright blue pointlike sources within 5 kpc of the nucleus of NGC 1275 using HST Planetary Camera observations is reported. The typical object has MV of about -12 to -14. They are all blue, with V - R of less than about 0.3. The color distribution and lack of excess H-alpha emission are consistent with nearly all being continuum sources. Many sources are unresolved even with the HST and consequently have sizes of less than about 15 pc. It is suggested that these are young star clusters that will evolve to look like globular clusters. They are bluer than any clusters seen in the Milky Way or M87, and brighter than the blue clusters seen in the LMC. Ages of several hundred million years or less and corresponding masses of 10 exp 5 - 10 exp 8 solar masses are derived.