Infall and Outflow of Molecular Gas in the Star forming Cores of Sgr B2

The molecular cloud Sgr B2 is one of the well-known massive star-forming region in our Galaxy. Sgr B2 is located in a special astrophysical environment near the Galactic center. ${\rm H_2CO}$ molecule is a useful probe to the physical conditions in the star forming region. Two fields centered at Sgr B2(N) and (M) were observed at 1.3 mm with the SMA including the two transitions of ${\rm H_2CO} (3_{03}-2_{02})~\&~(3_{21}-2_{20})$. Our results show that the majority of the dense molecular gas is falling into the major cores and the outflow traced by ${\rm H_2CO} (3_{21}-2_{20})$ appears to be decelerated from the Sgr B2(M) core. The preliminanry results has been published in GALACTIC CENTER WORKSHOP 2006 (Journal of Physics: Conference Series Volume 54, p468, 2006) Jun-Hui ZHAO
SMA image of Sgr B2 showing the dense molecular gas in the massive star forming cores. The color scale shows the intensity of ${\rm H_2CO} (3_{21}-2_{20})$. The contours are for ${\rm H_2CO} (3_{03}-2_{02})$. The spectra of ${\rm H_2CO} (3_{21}-2_{20})$ (red) and ${\rm H_2CO} (3_{03}-2_{02})$ (green) are shown towards several regions.