Globulars to 27.6 Magnitude in the Coma Cluster

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Session 52 -- Elliptical Galaxies
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[52.04] Globulars to 27.6 Magnitude in the Coma Cluster

W. A. Baum, M. Hammergren (U. Washington), R. M. Light, S. P. Ewald (Caltech), E. J. Groth (Princeton), E. A. Ajhar, T. R. Lauer, C. R. Lynds, E. J. O'Neil (KPNO), J. A. Holtzman (Lowell Obs.), S. M. Faber, C. J. Grillmair (Lick/UCSC)

We provide an updated report on exploratory HST-WFPC2 observations of NGC 4881, a bright E0 galaxy 18 arcmin from the center of the Coma Cluster. The redshift of the Coma Cluster, adjusted for local motion, is about 7200 km/sec. The two main results are: ~(1) ~We find NGC 4881 to have an unusually low specific frequency of globular clusters (GCs). That finding needs to be understood in terms of GC formation, migration, and survival in the environment of a dense cluster of galaxies. (2) ~Our photometry of NGC 4881's globular clusters also shows them to be increasing in number per 0.4--mag bin down to a threshold of $V = 27.6$ mag. We have evidently not yet passed the peak (turnover) of the GC luminosity function, which would yield a Coma distance based directly on GC distances in the Milky Way and M31. The threshold can be pushed fainter in NGC 4881 to seek the turnover if additional observations are made, but our present data are already of interest. If the turnover of the luminosity function is located at $M_V \approx -7.4$ mag (as in the Milky Way and M 31), our present result argues for a Coma Cluster distance $\geq 100$ Mpc.

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