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A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5

Geiles, Mark, Erkal, Denis, Antonini, Fabio, Balbinot, Eduardo and Penarrubia, Jorge 2021. A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5. Nature Astronomy 5 , pp. 957-966. 10.1038/s41550-021-01392-2
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Palomar 5 is one of the sparsest star clusters in the Galactic halo and is best known for its spectacular tidal tails, spanning over 20° across the sky. With N-body simulations, we show that both distinguishing features can result from a stellar-mass black hole population, comprising ~20% of the present-day cluster mass. In this scenario, Palomar 5 formed with a ‘normal’ black hole mass fraction of a few per cent, but stars were lost at a higher rate than black holes, such that the black hole fraction gradually increased. This inflated the cluster, enhancing tidal stripping and tail formation. A billion years from now, the cluster will dissolve as a 100% black hole cluster. Initially denser clusters end up with lower black hole fractions, smaller sizes and no observable tails. Black hole-dominated, extended star clusters are therefore the likely progenitors of the recently discovered thin stellar streams in the Galactic halo.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Nature Research
ISSN: 2397-3366
Date of First Compliant Deposit: 1 June 2021
Date of Acceptance: 7 May 2021
Last Modified: 13 Oct 2021 21:18

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