On the origin of the central 1″ hole in the stellar disk of sgr a* and the fermi gamma-ray bubbles

The supermassive black hole Sgr A* at the center of the Galaxy is surrounded by two misaligned disks of young, massive stars extending from 0.04 to 0.4 pc. The stellar surface density increases as r ^-2 toward Sgr A* but is truncated within 1″ (0.04 pc). We explore the origin of this annulus using a model in which star formation occurs in a disk of gas created through the partial capture of a gas cloud as it sweeps through the inner few parsecs of the galaxy and temporarily engulfs Sgr A*. We identify the locations within which star formation and/or accretion onto Sgr A* take place. Within 0.04 pc the disk is magnetically active and the associated heating and enhanced pressure prevents the disk from becoming self-gravitating. Instead, it forms a magneto-turbulent disk that drains onto Sgr A* in ≲ 3 × 10⁶ yr. Meanwhile, fragmentation of the gas beyond the central 0.04 pc hole creates the observed young stellar disk. The two large-scale bubbles of gamma-ray emission extending perpendicular to the Galactic plane may be created by a burst of accretion of 1 × 10 ⁵ M of gas lying between 0.01 and 0.03 pc. The observed stellar ages imply that this capture event occurred 10^6.5 yr ago, thus such events occurring over the lifetime of the Galaxy could have significantly contributed to the current mass of Sgr A* and to the inner few parsecs of the nuclear star cluster. We suggest that these events also occur in extragalactic systems.