ALMA observations of the Galactic center: SiO outflows and high-mass star formation near Sgr A*

F. Yusef-Zadeh*, M. Royster, M. Wardle, R. Arendt, H. Bushouse, D. C. Lis, M. W. Pound, D. A. Roberts, B. Whitney, A. Wootten

*Corresponding author for this work

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

ALMA observations of the Galactic center with a spatial resolution of 2.″61 × 0.″97 resulted in the detection of 11 SiO (5-4) clumps of molecular gas within 0.6 pc (15″) of Sgr A*, interior to the 2 pc circumnuclear molecular ring. The three SiO (5-4) clumps closest to Sgr A* show the largest central velocities, ≃150 km s-1, and the broadest asymmetric line widths with full width zero intensity (FWZI) ≃110-147 km s-1. The remaining clumps, distributed mainly to the NE of the ionized mini-spiral, have narrow FWZI (≃18-56 km s -1). Using CARMA SiO (2-1) data, Large Velocity Gradient modeling of the SiO line ratios for the broad velocity clumps constrains the column density N(SiO) ≃1014 cm-2, and the H2 gas density cm -3 for an assumed kinetic temperature 100-200 K. The SiO clumps are interpreted as highly embedded protostellar outflows, signifying an early stage of massive star formation near Sgr A* in the last 104-10 5 yr. Support for this interpretation is provided by the SiO (5-4) line luminosities and velocity widths which lie in the range measured for protostellar outflows in star-forming regions in the Galaxy. Furthermore, spectral energy distribution modeling of stellar sources shows two young stellar object candidates near SiO clumps, supporting in situ star formation near Sgr A*. We discuss the nature of star formation where the gravitational potential of the black hole dominates. In particular, we suggest that external radiative pressure exerted on self-shielded molecular clouds enhances the gas density, before the gas cloud becomes gravitationally unstable near Sgr A*. Alternatively, collisions between clumps in the ring may trigger gravitational collapse.

Original languageEnglish (US)
Article numberL32
JournalAstrophysical Journal Letters
Volume767
Issue number2
DOIs
StatePublished - Apr 20 2013

Keywords

  • Galaxy: center
  • ISM: jets and outflows
  • ISM: molecules
  • stars: protostars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Yusef-Zadeh, F., Royster, M., Wardle, M., Arendt, R., Bushouse, H., Lis, D. C., Pound, M. W., Roberts, D. A., Whitney, B., & Wootten, A. (2013). ALMA observations of the Galactic center: SiO outflows and high-mass star formation near Sgr A*. Astrophysical Journal Letters, 767(2), [L32]. https://doi.org/10.1088/2041-8205/767/2/L32