First evidence of fully spatially mixed first and second generations in globular clusters: the case of NGC 6362

TL;DR

This study provides the first evidence of fully spatially mixed multiple stellar populations in a low-mass globular cluster, NGC 6362, challenging previous assumptions about their spatial segregation.

Contribution

It demonstrates that NGC 6362 hosts two populations that are completely spatially mixed, supported by photometric analysis and simulations, which is unprecedented in globular cluster studies.

Findings

Both populations share the same radial distribution.

NGC 6362 is one of the least massive clusters with multiple populations.

The cluster likely lost up to 80% of its original mass.

Abstract

We present the first evidence of multiple populations in the Galactic globular cluster NGC 6362. We used optical and near-UV Hubble Space Telescope and ground based photometry, finding that both the sub giant and red giant branches are split in two parallel sequences in all color magnitude diagrams where the F336W filter (or U band) is used. This cluster is one of the least massive globulars (M_tot~5x10^4 M_sun) where multiple populations have been detected so far. Even more interestingly and at odds with any previous finding, we observe that the two identified populations share the same radial distribution all over the cluster extension. NGC 6362 is the first system where stars from different populations are found to be completely spatially mixed. Based on N-body and hydrodynamical simulations of multiple stellar generations, we argue that, to reproduce these findings, NGC 6362 should have lost up to the 80% of its original mass