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Our results are inconsistent with somerecent models of blue straggler formation that include collisionalformation mechanisms and may suggest that almost all observed bluestragglers are formed in binary systems.We present the first results of a large Advanced Camera for Surveys(ACS) survey of Galactic globular clusters.Inparticular, the location of the bump and the brightness of the tip ofthe red giant branch are problematic.
Several age indicators are thenfitted simultaneously, and the overall best-fitting isochrone isselected to determine the cluster age.
We also determine thegoodness-of-fit for different sets of indicators to estimate theconfidence level of our results. We find that ourisochrones provide no acceptable fit for all age indicators.
This Hubble Space Telescope(HST) Treasury project is designed to obtain photometry with S/N(signal-to-noise ratio) ~0.2 Msolar in a sample of globulars using the ACS Wide Field Channel.
Here we focus on clusters without previous HST imagingdata.
We find that the majority of the clusters have ages that are consistentwith the standard clusters at their metallicities.