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ALMA SiO (5-4) Observations: Protostellar Outflows near Sgr A*
Yusef-Zadeh, Farhad ( Northwestern University ); Royster, M. ( Northwestern University ); Wardle, M. ( Macquarie University, Australia ); Arendt, R. ( Crest/UMBC/NASA ); Bushouse, H. A. ( STScI ); Lis, D. C. ( Cal Tech ); Pound, M. W. ( U. of Maryland ); Roberts, D. A. ( Northwestern University ); Whitney, B. ( Space Science Institute ); Wootten, A. ( NRAO ) show affiliations
American Astronomical Society, AAS Meeting #222, #310.05
Published in Jun 2013
ALMA observations of the Galactic center resulted in the detection of a number of SiO (5-4) clumps of molecular gas in the 2-pc molecular ring orbiting Sgr A*. Eleven clumps of SiO (5-4) are also found within 0.6pc (15'') of Sgr A*. The three SiO (5-4) clumps closest to Sgr A* show the largest central velocities of ~150 km/s and broadest asymmetric linewidths with full width zero intensity (FWZI) 110-147 km/s. Other clumps beyond the inner 15'' show narrow linewidths (FWZI ~18-56 km/s. Using CARMA SiO (2-1) data, LVG modeling of the broad velocity clumps, constrain the H2 gas density (3-9)x10^5 cm^-3 for an assumed kinetic temperature 100-200K. The SiO clumps combined with evidence of YSO candidates are interpreted as highly embedded protostellar outflows, signifying an early stage of massive star formation near Sgr A* in the last 10^4-10^5 years. Star formation near Sgr A* is forbidden, unless the gas density is large enough for self-gravity to overcome the strong tidal shear of the back hole. We discuss different mechanisms that increase the gas density so that star formation can take place in this tidally stressed environment.
(c) 2013: American Astronomical Society