Exploiting Network Topology for Accelerated Bayesian Inference of Grain Surface Reaction Networks

• Published in: The Astrophysical journal Vol. 904; no. 2; pp. 197 - 211
• Main Authors: Heyl, Johannes, Viti, Serena, Holdship, Jonathan, Feeney, Stephen M.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-12-2020; IOP Publishing
• Subjects: Astrochemistry; Astrophysics; Astrostatistics strategies; Bayesian analysis; Dark interstellar clouds; Interstellar abundances; Interstellar chemistry; Interstellar matter; Interstellar medium; Network topologies; Organic chemistry; Reaction mechanisms; Reaction rates; Statistical inference; Surface chemistry; Surface reactions; Topology
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/abbeed

In the study of grain-surface chemistry in the interstellar medium, there exists much uncertainty regarding the reaction mechanisms with few constraints on the abundances of grain-surface molecules. Bayesian inference can be performed to determine the likely reaction rates. In this work, we consider methods for reducing the computational expense of performing Bayesian inference on a reaction network by looking at the geometry of the network. Two methods of exploiting the topology of the reaction network are presented. One involves reducing a reaction network to just the reaction chains with constraints on them. After this, new constraints are added to the reaction network and it is shown that one can separate this new reaction network into subnetworks. The fact that networks can be separated into subnetworks is particularly important for the reaction networks of interstellar complex-organic molecules, whose surface reaction networks may have hundreds of reactions. Both methods allow the maximum-posterior reaction rate to be recovered with minimal bias.