The Multiple Generations and Populations of the Massive Globular Cluster NGC 6273 (M 19)
Abstract
Although nearly all Galactic globular clusters exhibit large, and often correlated, star-to-star light element abundance variations, most systems do not display the same complexity for elements heavier than Si. In fact, the internal abundance variations of [Fe/H], [α/Fe], and heavier elements typically do not exceed ~10%. However, a growing number of the most massive clusters now show evidence of extended star formation and chemical enrichment histories, and at least two of these "iron-complex" globular clusters (ω Cen and M 54) are strongly suspected to have formed in or near the cores of accreted dwarf galaxies. In this context, we present new spectroscopic and photometric data for the massive cluster NGC 6273 obtained with the Magellan-M2FS and HST-WFC3 instruments. We find that NGC 6273 exhibits considerable chemical complexity, and was able to form at least 2-3 distinct generations of stars with different chemical compositions. The cluster also contains a trace population of α-poor stars, similar to the Sagittarius field population near M 54, that may have been accreted from a progenitor system.
- Publication:
-
American Astronomical Society Meeting Abstracts #229
- Pub Date:
- January 2017
- Bibcode:
- 2017AAS...22922105J