The Metallicity Distribution of Intracluster Stars in Virgo

We have used the Hubble Space Telescope's Advanced Camera for Surveys (ACS)to detect and measure ~5300 stars in a single intracluster field in the VirgoCluster. By performing F606W and F814W photometry on these stars, we havedetermined their metallicity distribution function, and constrained the typesof stars present in this portion of Virgo's intracluster space. Based on thesmall number of stars detected brighter than the red giant branch (RGB) tip, wesuggest that in this region, Virgo's intracluster stars are mostly old (>~10Gyr). Through analysis of the RGB stars themselves, we determine that thepopulation contains the full range of metallicities probed (-2.3<[M/H]<0.0). Wealso present evidence that the younger (<10 Gyr) component of the population ismore metal-rich, with [M/H]>-0.5. The spatial distribution of the mostmetal-poor stars in the field shows significantly more structure than that ofthe metal-rich stars, indicating that the intracluster population is notwell-mixed. We discuss the implications these observations have for theproduction of intracluster stars and the dynamical evolution of the VirgoCluster.Comment: 36 pages, 1 table, 13 figures (resolution lowered for Figs. 4, 6, and 7), accepted for publication in Ap