On the formation of glycolaldehyde in dense molecular cores

TL;DR

This study models glycolaldehyde formation in dense molecular cores at 10K, finding that certain grain-surface reactions, especially H3CO + HCO, are likely responsible for its observed abundance.

Contribution

It evaluates multiple formation mechanisms for glycolaldehyde, identifying the most chemically feasible grain-surface routes at low temperatures.

Findings

Gas-phase formation is unlikely.

Only two grain-surface routes are efficient at 10K.

H3CO + HCO is the most promising mechanism.

Abstract

Glycolaldehyde is a simple monosaccharide sugar linked to prebiotic chemistry. Recently it was detected in a molecular core in the star-forming region G31.41+0.31 at a reasonably high abundance. We investigate the formation of glycolaldehyde at 10K to determine whether it can form efficiently under typical dense core conditions. Using an astrochemical model, we test five different reaction mechanisms that have been proposed in the astrophysical literature, finding that a gas-phase formation route is unlikely. Of the grain-surface formation routes, only two are efficient enough at very low temperatures to produce sufficient glycolaldehyde to match the observational estimates, with the mechanism culminating in CH3OH + HCO being favoured. However, when we consider the feasibility of these mechanisms from a reaction chemistry perspective, the second grain-surface route looks more promising, H3CO + HCO.