The Spatial Scale of Glycolaldehyde in the Galactic Center

Abstract

We previously reported the spectral detection of the first interstellar sugar, which is known as glycolaldehyde (CH2OHCHO), by observing six separate millimeter-wave rotational transitions with the NRAO 12 m telescope while pointed toward the Sagittarius B2 North hot core source known as the Large Molecule Heimat (LMH) source. In the present BIMA array work, we have spatially mapped Sgr B2 using the 808-717 transition of glycolaldehyde at 82.4 GHz. We find that glycolaldehyde has a spatial scale of ≥60'' unlike its isomers methyl formate and acetic acid, which are concentrated in the LMH source that has a spatial scale of ≤5''. We estimate that the relative abundance ratios of (acetic acid) : (glycolaldehyde) : (methyl formate) are ~1 : 0.5 : 26 within the LMH source. It is likely that the conditions of the LMH source favor the chemically reactive nature of glycolaldehyde over its isomers and other large molecules such as dimethyl ether. The ensuing chemistry leads to glycolaldehyde destruction in the LMH source and glycolaldehyde survival outside of the LMH source in extended cloud extremities. This scenario is supported by comparison of line widths, which shows that glycolaldehyde possesses a factor of 2-3 greater line width than those of other complex molecules that are confined largely to the LMH source.