Searching for multiple populations in the integrated light of the young and extremely massive clusters in the merger remnant NGC 7252

Abstract

ABSTRACT Recent work has shown that the properties of multiple populations (MPs) within massive stellar clusters (i.e. in the extent of their abundance variations as well as the fraction of stars that show the anomalous chemistry) depend on the mass as well as the age of the host cluster. Such correlations are largely unexpected in current models for the formation of MPs and hence provide essential insight into their origin. Here, we extend our previous study into the presence or absence of MPs using integrated light spectroscopy of the ∼600 Myr, massive (∼107–108 M⊙) clusters, W3 and W30, in the galactic merger remnant, NGC 7252. Due to the extreme mass of both clusters, the expectation is that they should host rather extreme abundance spreads, manifested through high mean [Na/Fe] abundances. However, we do not find evidence for a strong [Na/Fe] enhancement, with the observations being consistent with the solar value. This suggests that age is playing a key role, or alternatively that MPs only manifest below a certain stellar mass, as the integrated light at all ages above ∼100 Myr is dominated by stars near or above the main-sequence turn-off.