Mapping observations of complex organic molecules around Sagittarius B2 with the ARO 12m telescope

We have performed high-sensitivity mapping observations of several complex organic molecules around Sagittarius B2 with the ARO 12m telescope at 3mm wavelength. Based on their spatial distribution, molecules can be classified as either 'extended', those detected not only in Sgr B2(N) and Sgr B2(M), or 'compact', those only detected toward or near Sgr B2(N) and Sgr B2(M). The 'extended' molecules include glycolaldehyde (CH₂OHCHO), methyl formate (CH₃OCHO), formic acid (t-HCOOH), ethanol (C₂H₅OH) and methyl amine (CH3NH₂), while the 'compact' molecules include dimethyl ether (CH₃OCH₃), ethyl cyanide (C₂H5CN), and amino acetonitrile (H₂NCH₂CN). These 'compact' molecules are likely produced under strong UV radiation, while the 'extended' molecules are likely formed at low temperatures, via gas-phase or grain-surface reactions. The spatial distribution of 'warm' CH₂OHCHO at 89 GHz differs 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-phasemodel, 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.