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Massive Star Formation of the SGR a East H (sub II) Regions Near the Galactic CenterA group of four compact H II regions associated with the well-known 50 km/s molecular cloud is the closest site of on-going star formation to the dynamical center of the Galaxy, at a projected distance of approximately 6 pc. We present a study of ionized gas based on the [Ne II] (12.8 micron) line, as well as multi-frequency radio continuum, Hubble Space Telescope Pa alpha, and Spitzer Infrared Array Camera observations of the most compact member of the H II group, Sgr A East H II D. The radio continuum image at 6 cm shows that this source breaks up into two equally bright ionized features, D1 and D2. The spectral energy distribution of the D source is consistent with it being due to a 25 =/- 3 solar mass star with a luminosity of 8 +/- 3 x 10(exp 4) Solar luminosity . The inferred mass, effective temperature of the UV source, and the ionization rate are compatible with a young O9-B0 star. The ionized features D1 and D2 are considered to be ionized by UV radiation collimated by an accretion disk. We consider that the central massive star photoevaporates its circumstellar disk on a timescale of 3x (exp 4) years giving a mass flux approximately 3 x 10(exp -5) Solar Mass / year and producing the ionized material in D1 and D2 expanding in an inhomogeneous medium. The ionized gas kinematics, as traced by the [Ne II] emission, is difficult to interpret, but it could be explained by the interaction of a bipolar jet with surrounding gas along with what appears to be a conical wall of lower velocity gas. The other H II regions, Sgr A East A-C, have morphologies and kinematics that more closely resemble cometary flows seen in other compact H II regions, where gas moves along a paraboloidal surface formed by the interaction of a stellar wind with a molecular cloud.
Document ID
20110015447
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1088/0004-637X/725/2/1429
Authors
Yusef-Zadeh, F. (Northwestern Univ. Evanston, IL, United States)
Lacy, J. H. (Texas Univ. Austin, TX, United States)
Wardle, M. (MacQuarie Univ. Sydney, Australia)
Whitney, B. (Space Science Inst. Boulder, CO, United States)
Bushouse, H. (Space Telescope Science Inst. Baltimore, MD, United States)
Roberts, D. A. (Adler Planetarium Chicago, IL, United States)
Arendt, R. G. (Maryland Univ. Baltimore County Greenbelt, MD, United States)
Date Acquired
August 25, 2013
Publication Date
December 20, 2010
Publication Information
Publication: The Astrophysical Journal
Volume: 725
Subject Category
Astrophysics
Report/Patent Number
GSFC.JA.4829.2011
Funding Number(s)
CONTRACT_GRANT: NSF-AST-0607312
CONTRACT_GRANT: NSF-AST-0807400
Distribution Limits
Public
Copyright
Public Use Permitted.

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