Formation of Complex Organic Molecules in Prestellar Cores: An Extended Model
We present the results of chemical modeling of the formation of terrestrial-type complex organic molecules (COMs) under conditions typical for prestellar cores. We utilized an advanced gas-grain astrochemical model with multilayer approach to ice-surface chemistry and up-to-date treatment of reactive desorption based on recent experiments of Minissale et al. (submitted). Chemical network in the model is based on Vasyunin&Herbst (2013) with certain updates to gas-phase and surface rections involving COMs. With the chemical model, radial profiles of molecules including COMs were calculated for the case of prototypical prestellar core L1544 at the moment of time when modeled depletion factor of CO became equal to that observed.
We found that terrestrial-type COMs can be formed efficiently in L1544 up to the fractional abundances of 10(-10) wrt. to H. Abundances of many COMs such as CH3OCH3, HCOOCH3, HCOOH and others peak at similar radial distance of ~4000 AU. Gas-phase abundances of COMs depend on the efficiency of reactive desorption, which is in turn depends on the composition of outer monolayers of icy mantles. In prestellar cores, outer monolayers of mantles are likely include large fraction of CO, which may increase the efficiency of reactive desorption according to Dulieu et al. (in prep.), and makes formation of COMs under conditions typical for prestellar cores efficient.