Massive star formation of the sgr a east hII regions near the galactic center

F. Yusef-Zadeh*, J. H. Lacy, M. Wardle, B. Whitney, H. Bushouse, D. A. Roberts, R. G. Arendt

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


A group of four compact HII regions associated with the well-known 50 km s-1 molecular cloud is the closest site of on-going star formation to the dynamical center of the Galaxy, at a projected distance of ∼6 pc. We present a study of ionized gas based on the [Ne ii] (12.8 μm) line, as well as multi-frequency radio continuum, Hubble Space Telescope Paα, and Spitzer Infrared Array Camera observations of the most compact member of the HII group, Sgr A East HII 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±3M star with a luminosity of 8±3×104 L. 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 3×104 years giving a mass flux ∼3 ±10-5 M yr-1 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 HII regions, Sgr A East A-C, have morphologies and kinematics that more closely resemble cometary flows seen in other compact HII regions, where gas moves along a paraboloidal surface formed by the interaction of a stellar wind with a molecular cloud.

Original languageEnglish (US)
Pages (from-to)1429-1439
Number of pages11
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 20 2010


  • Galaxy: center
  • Stars: early-type

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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