Analytical and Numerical Studies of Central Galactic Outflows Powered by Tidal Disruption Events: A Model for the Fermi Bubbles?

Abstract

Capture and tidal disruption of stars by the supermassive black hole in the Galactic center (GC) should occur regularly. The energy released and dissipated by these processes will affect both the ambient environment of the GC and the Galactic halo. The single star of a super-Eddington eruption generates a subsonic outflow with an energy release of more than 1052 erg, which still is not high enough to push shock heated gas into the halo. Only routine tidal disruption of stars near the GC can provide enough cumulative energy to form and maintain large-scale structures like the Fermi Bubbles. The average rate of disruption events is expected to be 10−4 ~ 10−5 yr−1, providing the average power of energy release from the GC into the halo of $dot{W}sim 3 imes {10}^{41}$ erg s−1, which is needed to support the Fermi Bubbles. The GC black hole is surrounded by molecular clouds in the disk, but their overall mass and filling factor are too low to significantly stall the shocks from tidal disruption events. The de facto continuous energy injection on timescales of megayears will lead to the propagation of strong shocks in a density stratified Galactic halo and thus create elongated bubble-like features that are symmetric to the Galactic midplane.