The ACS Survey of Galactic Globular Clusters. VII. Relative Ages

Understand

The ACS Survey of Galactic Globular Clusters is a Hubble Space Telescope (HST) Treasury program designed to provide a new large, deep and homogeneous photometric database.

• Based on observations from this program, we have measured precise relative ages for a sample of 64 Galactic globular clusters by comparing the relative position of the clusters' main sequence turn offs, using main-sequence fitting to cross-compare clusters within the sample.
• This method provides relative ages to a formal precision of 2-7%.
• We demonstrate that the calculated relative ages are independent of the choice of theoretical model.