Mapping Observations of complex organic molecules around Sagittarius B2
  with ARO 12m telescope
  We performed high-sensitivity mapping observations of several complex organic
molecules around Sagittarius B2 with ARO 12m telescope at 3-mm wavelength.
Based on their spatial distribution, molecules can be classified as either
"extended" that detected not only in Sgr B2(N) and Sgr B2(M), or "compact" that
only detected toward or near to Sgr B2(N) and Sgr B2(M). The "extended"
molecules including glycolaldehyde (CH2OHCHO), methyl formate (CH3OCHO), formic
acid (t-HCOOH), ethanol (C2H5OH) and methyl amine (CH3NH2), while the "compact"
molecules including dimethyl ether (CH3OCH3), ethyl cyanide (C2H5CN), and amino
acetonitrile (H2NCH2CN). These "compact" molecules are likely produced under
strong UV radiation, while "extended" molecules are likely formed under
low-temperature, via gas-phase or grain surface reactions. The spatial
distribution of "warm" CH2OHCHO at 89 GHz differ from the spatial distribution
of "cold" CH2OHCHO observed at 13 GHz. We found evidence for an overabundance
of CH2OHCHO compared to that expected from the gas-phase model, which indicates
that grain-surface reactions are necessary to explain the origin of CH2OHCHO in
Sagittarius B2. Grain-surface reactions are also needed to explain the
correlation between the abundances of "cold" CH2OHCHO and C2H5OH. These results
demonstrate the importance of grain-surface chemistry in the production of
complex organic molecules.
