Dominant molecular formation pathway

Determine which formation pathway—gas-phase chemistry or chemistry on dust grains—dominates for a particular interstellar molecule under specified physical conditions.

Background

The paper investigates molecular formation in the massive star-forming region RCW 120, where molecules can form through gas-phase reactions or on the surfaces and mantles of dust grains. Although observational and modelling studies identify likely pathways for several species, molecules such as water may have multiple competing formation channels. The authors explicitly identify determining the dominant pathway for a particular molecule as an unresolved general problem; the present study uses molecular column-density correlations and astrochemical modelling to investigate, but does not solve, this question universally.