Chemical Variation among Protostellar Cores: Dependence on Prestellar Core Conditions

TL;DR

This study investigates how prestellar core conditions influence the chemical complexity in star-forming regions, revealing dependencies of hot corino and WCCC chemistry on temperature, extinction, and static phase duration.

Contribution

It introduces a layered ice-mantle chemical model to analyze the impact of static phase conditions on complex organic molecule formation in protostellar cores.

Findings

WCCC activity increases with lower temperature and extinction.

COM formation varies with static phase temperature and photolysis effects.

Static phase duration has minimal impact on COM abundances.

Abstract

Hot corino chemistry and warm carbon chain chemistry (WCCC) are driven by gas-grain interactions in star-forming cores: radical-radical recombination reactions to form complex organic molecules (COMs) in the ice mantle, sublimation of CH$_4$ and COMs, and their subsequent gas-phase reactions. These chemical features are expected to depend on the composition of ice mantle which is set in the prestellar phase. We calculated the gas-grain chemical reaction network considering a layered ice-mantle structure in star-forming cores, to investigate how the hot corino chemistry and WCCC depend on the physical condition of the static phase before the onset of gravitational collapse. We found that WCCC becomes more active, if the temperature is lower, or the visual extinction is lower in the static phase, or the static phase is longer. Dependence of hot corino chemistry on the static-phase condition is more complex. While CH$_3$OH is less abundant in the models with warmer static phase, some COMs are formed efficiently in those warm models, since there are various formation paths of COMs. If the visual extinction is lower, photolysis makes COMs less abundant in the static phase. Once the collapse starts and visual extinction increases, however, COMs can be formed efficiently. Duration of the static phase does not largely affect COM abundances. Chemical diversity between prototypical hot corinos and hybrid sources, in which both COMs and carbon chains are reasonably abundant, can be explained by the variation of prestellar conditions. Deficiency of gaseous COMs in prototypical WCCC sources is, however, hard to reproduce within our models.