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 100 massive, high-velocity young stars whose existence, and organization of a subset of them in one, or possibly two, misaligned 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 overpressured 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 of 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, can account for multiple disks of stars with uncorrelated orientations.

Stellar Black Holes Can “Stretch” Supermassive Black Hole Accretion Disks

“…The outer regions of the accretion disk are far from the central supermassive black hole (SMBH), where self-gravity plays a dominant role, and the disk inevitably collapses to form stars (e.g., Kolykhalov & Syunyaev 1980;Shlosman & Begelman 1989). Nuclear star formation can also be triggered by jetted tidal disruption events in SMBHs (e.g., Perna & Grishin 2022). In addition, stars near the center of the galaxy can interact with the SMBH accretion disk, resulting in a loss of orbital energy and angular momentum, and are captured by the accretion disk (e.g., Syer et al 1991;Cantiello et al 2021).…”