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Chemical Abundances and Kinematics of the Tidally Disrupting Metal-Poor Globular Cluster ESO280-SC06

Presentation #404.05 in the session Stellar Populations & Evolution — iPoster Session.

Published onJun 29, 2022
Chemical Abundances and Kinematics of the Tidally Disrupting Metal-Poor Globular Cluster ESO280-SC06

Globular Clusters (GCs) are compact, gravitationally bound, ancient systems containing up to 10 million stars that mostly orbit in galactic halos. GC stars were originally thought to have identical chemical abundances, since the stars were born in the same molecular cloud. However, observations show GCs ubiquitously contain chemically anomalous stars that are enhanced in light elements like N, Na, O, and Al. There is no definitive answer to the origin of these anomalies yet. Although chemically anomalous stars have been detected in all GCs to date, there has not been any data in most metal-poor and least luminous GCs so far. ESO280-SC06 is one of the least luminous and most metal-poor intact globular clusters known in the Milky Way. We performed the first chemical abundance analysis of ESO280-SC06 with high-resolution echelle spectra of 10 stars from Magellan/MIKE. Based on their N, Na, and Al abundances, we find 6/10 stars to have anomalous abundances. GCs tend to contain fewer chemically anomalous stars as they decrease in luminosity. ESO280-SC06 has twice as many chemically anomalous stars as expected for its luminosity. This either indicates that the most metal-poor GCs have unusually large numbers of chemically anomalous stars, or that ESO280-SC06 used to be more luminous but has lost mass to tidal disruption. We thus also determined the kinematics and orbit of ESO280-SC06. Based on this, we conclude that ESO280-SC06 was previously more massive with substantial mass loss due to tidal disruption. Our results emphasize the importance of considering tidal disruption when studying globular clusters, both in the Milky Way and beyond.

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