Dynamical evolution of the young stars in the Galactic center: N-body simulations of the S-stars

Abstract

We use N-body simulations to study the evolution of the orbital eccentricities of stars deposited near (<0.05 pc) the Milky Way massive black hole (MBH), starting from initial conditions motivated by two competing models for their origin: formation in a disk followed by inward migration; and exchange interactions involving a binary star. The first model predicts modest eccentricities, lower than those observed in the S-star cluster, while the second model predicts higher eccentricities than observed. The N-body simulations include a dense cluster of 10 M_sun stellar black holes (SBHs), expected to accumulate near the MBH by mass segregation. Perturbations from the SBHs tend to randomize the stellar orbits, partially erasing the dynamical signatures of their origin. The eccentricities of the initially highly eccentric stars evolve, in 20 Myr (the S-star lifespan), to a distribution that is consistent at the ~95 % level with the observed eccentricity distribution. In contrast, the eccentricities of the initially more circular orbits fail to evolve to the observed values in 20 Myr, arguing against the disk migration scenario. We find that 20 % - 30 % of the S-stars are tidally disrupted by the MBH over their lifetimes, and that the S-stars are not likely to be ejected as hypervelocity stars outside the central 0.05 pc by close encounters with stellar black holes.

6 pages, 2 figures. Minor corrections, Sumitted to ApJ

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• A numerical study of vector resonant relaxation
• The young stars in the Galactic Center
• On post-Newtonian orbits and the Galactic-center stars
• Formation and evolution of nuclear star clusters with in-situ star-formation: Nuclear cores and age segregation
• The S-Star Cluster at the Center of the Milky Way: On the nature of diffuse NIR emission in the inner tenth of a parsec
• Steeper stellar cusps in galactic centers from binary disruption
• Where intermediate-mass black holes could hide in the Galactic Centre: A full parameter study with the S2 orbit
• The statistical mechanics of relativistic orbits around a massive black hole
• Massive binary star mergers in galactic nuclei: implications for blue stragglers, binary S-stars and gravitational waves
• On the Newtonian and Spin-induced Perturbations felt by the Stars Orbiting around the Massive Black Hole in the Galactic Center
• Star cluster disruption by a massive black hole binary
• Star formation at the Galactic Centre: coevolution of multiple young stellar discs
• The properties of hypervelocity stars and S-stars originating from an eccentric disc around a supermassive black hole
• Forming Young and Hypervelocity Stars in the Galactic Centre via Tidal Disruption of a Molecular Cloud
• Evolution of eccentric stellar disks around supermassive black holes: the complex disk disruption dynamics and the milliparsec stars
• Sculpting the Stellar Cusp in the Galactic Center
• Probing the formation of planetesimals in the Galactic Centre using Sgr A* flares
• The S stars' zone of avoidance in the Galactic center
• Astrophysics with the Laser Interferometer Space Antenna
• Double progenitor origin of the S-star cluster
• A Recent Supermassive Black Hole Binary in the Galactic Center Unveiled by the Hypervelocity Stars
• Disks of Stars in the Galactic center triggered by Tidal Disruption Events
• A solution to the paradox of youth in the Galactic centre