http://arxiv.org/abs/2102.11348
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 at present day. Black hole-dominated, extended star clusters are therefore the likely progenitors of the recently discovered thin stellar streams in the Galactic halo.
M. Gieles, D. Erkal, F. Antonini, et. al.
Wed, 24 Feb 21
21/64
Comments: 32 pages, 7 figures, 3 tables, submitted to Nature Astronomy
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