Dynamical evolution of Milky Way globular clusters on the cosmological timescale

I. Mass loss and interaction with the nuclear star cluster

¹ Main Astronomical Observatory, National Academy of Sciences of Ukraine, 27 Akademika Zabolotnoho St, 03143 Kyiv, Ukraine
² Nicolaus Copernicus Astronomical Centre Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
³ Fesenkov Astrophysical Institute, Observatory 23, 050020 Almaty, Kazakhstan
⁴ Heriot-Watt International Faculty, K. Zhubanov Aktobe Regional University, Zhubanov Broth. Str. 263, 030000 Aktobe, Kazakhstan
⁵ Energetic Cosmos Laboratory, Nazarbayev University, Kabanbay Batyr Ave. 53, 010000 Astana, Kazakhstan
⁶ Faculty of Physics and Technology, Al-Farabi Kazakh National University, Al-Farabi Ave. 71, 050040 Almaty, Kazakhstan
⁷ Rudolf Peierls Centre for Theoretical Physics, Parks Road, OX1 3PU Oxford, UK
⁸ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, HUN-REN CSFK, MTA Centre of Excellence, Konkoly Thege Miklós út 15-17, 1121 Budapest, Hungary

Received: 16 April 2024
Accepted: 10 June 2024

Abstract

Context. Based on the Gaia DR3, we reconstructed the orbital evolution of the known Milky Way globular clusters and found that six objects, NGC 6681, NGC 6981, Palomar 6, NGC 6642, HP 1, and NGC 1904, very likely interact closely with the nuclear star cluster.

Aims. We study the dynamical evolution of selected Milky Way globular clusters and their interactions with the Galactic centre over cosmological timescales. We examine the global dynamical mass loss of these globular cluster systems, their close interactions with the Galactic centre, and the potential capture of stars by the Milky Way nuclear star cluster.

Methods. For the dynamical modelling of the clusters, we used the parallel N-body code φ-GPU, which allows star-by-star simulations of the systems. Our current code also enabled us to follow the stellar evolution of individual particles, including the formation of high-mass remnants. The modelling was carried out in a Milky Way-like, time-variable potential (with a dynamically changing mass and scale length), obtained from the IllustrisTNG-100 database, with a full integration time of eight billion years.

Results. Based on extensive numerical modelling and analysis, we estimated the mass loss and the global and inner structures of the selected six clusters. Over an evolution of eight billion years, the clusters lost ≈80% of their initial mass. We analysed the phase-space evolution of the individual unbound stars NGC 6681, NGC 6642, HP 1, and NGC 1904. We found that only NGC 6642 could potentially have been a source for populating the Milky Way nuclear star cluster in the past.