Dynamical evolution of Milky Way globular clusters on the cosmological timescale II. Terzan 2, 4, and 5 mass loss and collision tracking

Abstract

We investigate the long-term dynamical evolution of Ter2, Ter4, and Ter5, focusing on their mutual interactions, mass-loss behaviour, and survivability in the dense Galactic centre environment. We performed a suite of high-resolution direct N-body simulations over 8 Gyr, modelling three individual clusters that we also modelled as combined systems. We compared reference runs of isolated clusters with simulations of the full three-cluster system to quantify possible differences in mass loss, potential energy, and orbital behaviour. Our simulations reveal multiple close encounters between the Terzan clusters. The most significant encounters occur between Ter2-Ter4 and Ter4-Ter5, with their tidal radii exceeding the minimum separation. A notable case is the pair Ter2-Ter4, which approaches within 10 pc at a relative velocity of ~320 km/s. We found that the mass-loss rate is higher for the low-mass Ter2 and Ter4 systems in the combined three-cluster simulations than in our similar isolated runs, highlighting the importance of mutual cluster interactions. The common run clearly demonstrates that mutual gravitational interactions between clusters drive significant triaxial deformations, especially for Ter2 and Ter5, which evolve from nearly spherical to distinctly prolate shapes. In contrast, the isolated runs show clusters that remained almost perfectly spherical, confirming that the observed shape changes are correlated with the mutual interactions. The survivability and dynamical evolution of Galactic centre globular clusters cannot be fully understood without accounting for collective interactions among all systems within a few kiloparsecs. Our results emphasise the necessity of complex multi-cluster modelling in realistic Galactic potentials to capture the long-term fate of surviving and dissolved clusters