RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 10 June 2016, 14:00-14:20; Duffield Lecture Theatre

Chengyuan Li

"Using the sub-giant branch to constrain the star formation history of intermediate-age clusters"

The presence of extended main-sequence turn-off (eMSTO) regions in intermediate-age, 1–2 Gyr-old star clusters in the Large and Small Magellanic Clouds is often interpreted as resulting from extended star-formation histories (SFHs) that last ≥ 300 Myr. This strongly conflicts with the traditional view of stellar clusters, which are thought of as single-aged stellar populations. In this talk, I will show our investigation into these issues by exploring the morphology of the sub-giant branch (SGB) of LMC and SMC clusters. We find that for most cases, the width of the SGB favors the single-aged stellar population interpretation and rules out an extended SFH. For clusters that have a very low escape velocity, they have unlikely undergone significant mass loss at an early stage, thus indicating that they may lack the capacity to capture most of their initial, expelled gas from stellar evolutionary processes.