Poster Title: GLOBULAR CLUSTERS AS PROBES OF GALAXY EVOLUTION
Abstract: If globular clusters form during major mergers between galaxies their age distribution should provide a strong test to galaxy formation theories. We present the results of our analysis on the UBV photometric data of globular clusters in the elliptical galaxy NGC 5128 (Cen A). We used U-B as metallicity indicator. We show that, unlike other popular broadband colours (e.g., V-I), U-B is free from the age-metallicity degeneracy and thus uniquely determines metallicity using Milky Way cluster data. Then, we apply the technique to the clusters of NGC 5128 and found the following. There is a large spread in U-B, which corresponds to [Fe/H] of -2.3 through possibly over +0.3 and a large spread in B-V, which corresponds to ages of 2 through 13 Gyr. Yet, for a given metallicity, the scatter in age is very small. The derived mean age estimate gradually decreases with increasing metallicity, indicating a strikingly well-defined age-metallicity relation, unseen anywhere ever before. The result, if interpreted naively, supports the scenario in which globular clusters form episodically throughout redshifts since early universe, a prediction of hierarchical galaxy formation scenarios. We show that an even stronger test can be made if far-UV data, which can be obtained using HST and GALEX, are additionally provided.
Link to poster: N/A