Tidal Disruption of Stellar Clusters and the Spatial Distribution of Their Remnants Near the Galactic Center

Abstract

The accretion of massive star clusters via dynamical friction has previously been established to be a likely scenario for the buildup of nuclear stellar clusters (NSCs). A remaining issue is whether strong external tidal perturbation may lead to the severe disruption of loosely bound clusters well before they sink deeply into the center of their host galaxies. We carry out a series of N-body simulations and verify our early idealized analytic models. We show that if the density profile of the host galaxies can be described by a power-law distribution with an index of α < 1, the cluster would be compressed in the radial direction by the external galactic tidal field. In contrast, the galactic tidal perturbation is disruptive in regions with a steep, α > 1, density falloff or in the very center where gravity is dominated by the point-mass potential of supermassive black holes (SMBHs). This sufficient criterion supplements the conventional necessary Roche-lobe-filling condition in determining the preservation versus disintegration of satellite stellar systems. We simulate the disruption of stellar clusters that venture onto nearly circular, modestly, or highly eccentric orbits into the center of galaxies with a range of background density profiles and SMBHs. We obtain the spatial distribution of the stellar cluster remnants. We apply these results to the NSC within a few parsecs from SMBH Sgr A* at the Galactic Center. Recent observations indicate the coexistence of two populations of stars with distinctively separate ages and metallicities. We verify that the subsolar-metallicity population can be the debris of disrupted stellar clusters.