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 \sim 6 pc .
We present a study of ionized gas based on the [ NeII ] ( 12.8 \mu m ) line , as well as multi-frequency radio continuum , HST Pa \alpha and Spitzer IRAC observations of the most compact member of the HII group , Sgr A East HII D. The radio continuum image at 6cm shows that this source breaks up into two equally bright ionized features , D1 and D2 .
The SED of the D source is consistent with it being due to a 25 \pm 3 M _ { \odot } star with a luminosity of 8 \pm 3 \times 10 ^ { 4 } \hbox { L } _ { \odot } .
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 \times 10 ^ { 4 } years giving a mass flux \sim 3 \times 10 ^ { -5 } M _ { \odot } 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 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 .