Milone, Antonino; Bedin, L R; Piotto, G; Anderson, J; King, I R; Sarajedini, A; Dotter, Aaron; Chaboyer, Brian; Marin-Franch, A; Majewski, S; Aparicio, A; Reid, I Neill; Paust, Nathaniel
Photometry with the Hubble Space Telescope Advanced Camera for Surveys (HSTACS) reveals that the subgiant branch (SGB) of the globular cluster NGC 1851 splits into two well-defined branches. If the split is due only to an age effect, the two SGBs would imply two star formation episodes separated by ~1 Gyr. We discuss other anomalies in NGC 1851 that could be interpreted in terms of a double stellar population. Finally, we compare the case of NGC 1851 with the other two globulars known to host...[Show more]
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