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The peculiar kinematics of the multiple populations in the globular cluster Messier 80 (NGC 6093)

S. Kamann, E. Dalessandro, N. Bastian, J. Brinchmann, M. den Brok, S. Dreizler, B. Giesers, F. Göttgens, T.-O. Husser, D. Krajnović, G. van de Ven, L. L. Watkins, L. Wisotzki

Abstract
We combine MUSE spectroscopy and Hubble Space Telescope ultraviolet (UV) photometry to perform a study of the chemistry and dynamics of the Galactic globular cluster Messier 80 (M80, NGC 6093). Previous studies have revealed three stellar populations that vary not only in their light-element abundances, but also in their radial distributions, with the concentration decreasing with increasing nitrogen enrichment. This remarkable trend, which sets M80 apart from other Galactic globular clusters, points towards a complex formation and evolutionary history. To better understand how M80 formed and evolved, revealing its internal kinematics is key. We find that the most N-enriched population rotates faster than the other two populations at a 2σ confidence level. While our data further suggest that the intermediate population shows the least amount of rotation, this trend is rather marginal (1-2σ). Using axisymmetric Jeans models, we show that these findings can be explained from the radial distributions of the populations if they possess different angular momenta. Our findings suggest that the populations formed with primordial kinematical differences.

Keywords
stars: abundances; stars: kinematics and dynamics; globular clusters: individual: M80; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Astrophysics of Galaxies

Monthly Notices of the Royal Astronomical Society
Volume 492, Issue 1, Page 966
2020 February

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Instituto de AstrofĆ­sica e CiĆŖncias do EspaƧo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
FundaĆ§Ć£o para a CiĆŖncia e a Tecnologia COMPETE 2020 PORTUGAL 2020 UniĆ£o Europeia