Globular clusters in the Galactic center region: Expected behavior within the infall and merger scenario

Abstract

In this work, we reexamine the infall and merger scenario of massive clusters in the Milky Way’s potential well as a plausible Milky Way formation mechanism. We aim to understand how the stars of the merging clusters are redistributed during and after the merger process. We used, for the first time, high-resolution simulations with concentrated in the 300 pc around the Galactic center. We adopted simulations developed in the framework of the Modelling the Evolution of Galactic Nuclei (MEGaN) project. We compared the evolution of representative clusters in the mass and concentration basis in the vicinity of a supermassive black hole. We used the spatial distribution, density profile, and the 50% Lagrange radius (half mass radius) as indicators along the complete simulation to study the evolutionary shape in physical and velocity space and the final fate of these representative clusters. We find that the least massive clusters are quickly (< 10 Myr) destroyed. On the other hand, the most massive clusters have a long evolution, showing variations in the morphology, especially after each passage close to the supermassive black hole. The deformation of the clusters depends on the concentration, with general deformations for the least concentrated clusters and outer strains for the more concentrated ones. At the end of the simulation, a dense concentration of stars belonging to the clusters was formed. The particles that belong to the most massive and most concentrated clusters are concentrated in the innermost regions, meaning that the most massive and concentrated clusters contribute a more significant fraction of particles to the final concentration. This finding suggests that the population of stars of the nuclear star cluster formed through this mechanism comes from massive clusters rather than low-mass globular clusters.