Disks of Stars in the Galactic center triggered by Tidal Disruption Events

Abstract

In addition to a supermassive black hole (SMBH), the central parsec of the Milky Way hosts over a hundred of massive, high velocity young stars whose existence, and organisation of a subset of them in one, or possibly two, mis-aligned disks, is puzzling. Due to a combination of low medium density and strong tidal forces in the vicinity of Sgr A*, stars are not expected to form. Here we propose a novel scenario for their in-situ formation: a jetted tidal disruption event (TDE) from an older wandering star triggers an episode of positive feedback of star formation in the plane perpendicular to the jet, as demonstrated via numerical simulations in the context of jet-induced feedback in galactic outflows. An over-pressured cocoon surrounding the jet shock-compresses clumps to densities high enough to resist the SMBH tidal field. The TDE rate of $10^{-5}-10^{-4}$ yr${}^{-1}$ per galaxy, out of which a few percent events are jetted, implies a jetted TDE event per galaxy to occur every few million years. This timescale is interestingly of the same order of the age of the disk stars. The mass function predicted by our mechanism is top-heavy. Additionally, since TDEs are isotropic, our model predicts a random orientation for the disk of stars with respect to the plane of the galaxy and, due to the relatively high TDE rate, it can account for multiple disks of stars with uncorrelated orientations.

ApJL in press

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