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

Mark Wardle, Farhad Yusef-Zadeh

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

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 106.5 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.

Original languageEnglish (US)
Article numberL14
JournalAstrophysical Journal Letters
Volume787
Issue number1
DOIs
StatePublished - May 20 2014

Keywords

  • Galaxy: center
  • accretion, accretion disks
  • galaxies: active
  • gamma rays: galaxies
  • magnetohydrodynamics (MHD)
  • stars: formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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