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We present the results of combining Hubble Space Telescope optical photometry with ground-based Ks-band photometry from the Gemini imagers NIRI and FLAMINGOS-I to study the globular-cluster populations in four early-type galaxies that are candidate r emnants of recent mergers (NGC1700, NGC2865, NGC4382, and NGC7727). These galaxies were chosen based on their blue colors and fine structure, such as shells and ripples that are indicative of past interactions. We fit the combined VIKs globular-cluster data with simple toy models of mixed cluster populations that contain three subpopulations of different age and metallicity. The fits, done via Chi-square mapping of the parameter space, yield clear evidence for the presence of intermediate-age clusters in each galaxy. We find that the ages of 1-2 Gyr for these globular-cluster subpopulations are consistent with the previously estimated merger ages for the host galaxies.
89 - Bryan W. Miller 2007
The globular cluster luminosity function, specific globular cluster frequency, S_N, specific globular cluster mass, T_MP, and globular cluster mass fraction in dwarf elliptical galaxies are explored using the full 69 galaxy sample of the HST WFPC2 Dw arf Elliptical Galaxy Snapshot Survey. The GCLFs of the dEs are well-represented with a t_5 function with a peak at M_{V,Z}^0(dE,HST) = -7.3 +/- 0.1. This is ~0.3 magnitudes fainter than the GCLF peaks in giant spiral and elliptical galaxies, but the results are consistent within the uncertainties. The bright-end slope of the luminosity distribution has a power-law form with slope alpha = -1.9 +/- 0.1. The trend of increasing S_N or T_MP with decreasing host galaxy luminosity is confirmed. The mean value for T_MP in dE,N galaxies is about a factor of two higher than the mean value for non-nucleated galaxies and the distributions of T_MP in dE,N and dE,noN galaxies are statistically different. These data are combined with results from the literature for a wide range of galaxy types and environments. At low host galaxy masses the distribution of T_MP for dE,noN and dI galaxies are similar. This supports the idea that one pathway for forming dE,noN galaxies is by the stripping of dIs. The formation of nuclei and the larger values of T_MP in dE,N galaxies may be due to higher star formation rates and star cluster formation efficiencies due to interactions in galaxy cluster environments.
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