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

TL;DR

This study maps complex organic molecules around Sagittarius B2, revealing their spatial distribution and suggesting grain-surface chemistry plays a key role in their formation, with implications for astrochemical processes.

Contribution

It provides high-resolution mapping of complex organic molecules around Sagittarius B2, distinguishing between 'extended' and 'compact' molecules and highlighting the importance of grain-surface reactions.

Findings

'Extended' molecules detected over larger regions, 'compact' molecules near Sgr B2.

Grain-surface reactions are necessary to explain CH2OHCHO abundance.

Spatial distribution differences indicate varied formation conditions.

Abstract

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.