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The Peculiar Radial Distribution of Multiple Populations in the Massive Globular Cluster M80

Dalessandro, E, Cadelano, M, Vesperini, E, Salaris, M, Ferraro, FR, Lanzoni, B, Raso, S, Hong, J, Webb, JJ and Zocchi, A (2018) The Peculiar Radial Distribution of Multiple Populations in the Massive Globular Cluster M80. Astrophysical Journal, 859 (1). ISSN 0004-637X

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Abstract

We present a detailed analysis of the radial distribution of light-element multiple populations (LE-MPs) in the massive and dense globular cluster M80, based on a combination of UV and optical Hubble Space Telescope data. Surprisingly, we find that first-generation (FG) stars (FG) are significantly more centrally concentrated than extreme second-generation (SG) stars out to ∼2.5rhfrom the cluster center. To understand the origin of such peculiar behavior, we used a set of N-body simulations following the long-term dynamical evolution of LE-MPs. We find that, given the advanced dynamical state of the cluster, the observed difference does not depend on the primordial relative distributions of FG and SG stars. On the contrary, a difference of ∼0.05-0.10 Mobetween the average masses of the two subpopulations is needed to account for the observed radial distributions. We argue that such a mass difference might be the result of the higher He abundance of SG stars (of the order of ΔY ∼0.05-0.06) with respect to FG stars. Interestingly, we find that a similar He variation is necessary to reproduce the horizontal branch morphology of M80. These results demonstrate that differences in mass among LE-MPs, due to different He content, should be properly taken into account for a correct interpretation of their radial distribution, at least in dynamically evolved systems. © 2018. The American Astronomical Society. All rights reserved..

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society; IOP Publishing
Date Deposited: 25 Jun 2018 09:38
Last Modified: 25 Jun 2018 09:38
DOI or Identification number: 10.3847/1538-4357/aabb56
URI: http://researchonline.ljmu.ac.uk/id/eprint/8885

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