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Updated: Jun 5, 2025

Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5
Mark Gieles1,2, Denis Erkal3, Fabio Antonini4
1ICREA, Pg. Lluís Companys 23, E08010 Barcelona, Spain.
Abstract:
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 degrees 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 gigayear 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.
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