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Session 64 - Globular Clusters.
Oral session, Tuesday, January 14
I have undertaken a systematic survey of dwarf elliptical galaxies in order to find and study their globular cluster systems (GCSs). The sample represents 11 dE/dE,N galaxies in the Virgo cluster and the bright dE,N NGC 3115 DW1. In 10 of the galaxies a likely GCS has been detected as a > 1 \sigma excess of stellar-like objects. The mean specific frequency of GCs for dE galaxies is \sim 4 (for both dEs and dE,Ns), very similar to that found in giant elliptical galaxies, and higher than that in spirals. Lower-luminosity dEs have larger specific frequencies and may be due to significant mass loss at various epochs. The mass spectrum of the GCSs around 8 Virgo dE,Ns and NGC 3115 DW1 have slopes of \sim -1.8 to -1.9, in very good agreement with that observed for GCSs around giant (spiral and elliptical) galaxies. This suggests that the globular clusters formed via the same mechanism in galaxies of all masses and morphologies. These results are also consistent with the picture where GC's formed in the cores of supergiant molecular clouds (Harris amp; Pudritz 1994, ApJ, 429, 177). For 3 galaxies for which colors were obtained the GCs are bluer (in the mean) than that of the galaxy light, suggesting the GCs are more metal-poor (by \sim 0.5 dex in [Fe/H]) than the galaxy halo stars. However, the presently observed GCS would have been unable to create this offset; it would likely have arisen from a combination of a shallower IMF, other sites of star formation and a larger GC population.
Program listing for Tuesday