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Arunav Kundu (STScI/U. Maryland), B.C. Whitmore (STScI)
We present an analysis of the properties of the globular cluster systems (GCS) of over 50 Elliptical and S0 galaxies from HST-WFPC2 wide band images in multiple colors. The metallicity and spatial distributions of the globular clusters hold vital clues about the formation and evolutionary history of the globular cluster systems and their host galaxies. We find evidence of bimodal color distributions in nearly half of our sample galaxies, and in each case we find that the more metal rich clusters are closer to the center of the galaxy than the metal poor ones. The merger model of globular cluster formation satisfactorily explains the properties of the GCS of galaxies with bimodal distributions. However the metal rich cluster population in some S0 galaxies (e.g. NGC 3115) appear to be associated with a thick disk unlike the more spherical distribution in elliptical galaxies, which suggests that these S0 galaxies have not undergone a major merger in their history. We present the first detailed study of the GCSs of S0 galaxies
We also study the globular cluster luminosity function (GCLF) of the candidate galaxies and it's suitability as a distance indicator. Our studies indicate that the distances derived using the turnover luminosity of the GCLF are consistent with those derived from other methods like surface brightness fluctuations and have comparable errors. We report on the effect of environment, color and galaxy type on the absolute value of the turnover luminosity of the GCLF. The superior angular resolution of the HST enabled us to measure, for the first time, the half light radius (rh) of individual clusters in a large number of galaxies. We find that the median value of rh in most galaxies is \approx3 pc. We suggest that it may be possible to use this value for secondary distance calibrations.
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