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Session 83 - Elliptical Galaxies.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
Globular clusters surrounding IC 4051, the sixth brightest elliptical galaxy in the Coma Cluster (redshift \approx 7200 km/sec), were recently observed with HST--WFPC2 in an effort to locate the ``turnover'' magnitude of the globular cluster luminosity function (GCLF). The turnover is a distance indicator directly linking Coma to objects in the Milky Way without involving intermediate distance markers such as the Virgo Cluster. The possible dependence of the GCLF on galaxy type and environment is being addressed in other studies.
We obtained eight full-orbit WFPC2 exposures (totaling 20,500 sec) with the F606W filter and two (totaling 5,200 sec) with F814W. These IC 4051 observations reach F606W \sim 28.1 mag, which probes the GCLF about 0.8 mag deeper than obtained earlier with WFPC2 in the Coma elliptical NGC 4881 (Baum et al., AJ, Dec 1995). Like NGC 4881, IC 4051 is located far from the center of the Coma Cluster, but it has roughly 10 times as many globulars. As in NGC 4881, the globulars of IC 4051 have a small dispersion in color index.
Our NGC 4881 data implied a minimum Coma distance of 108 Mpc (with a formal error of -11 Mpc), which corresponds to a maximum H_0 value of 67 km/sec per Mpc (with a formal error of +7 km/sec per Mpc). At the AAS meeting we will present a status report on the equivalent analysis of the IC 4051 data.
Program listing for Wednesday