Chemical model of protostellar cores and applications

Abstract

Interstellar complex organic molecules (iCOMs) are thought to form on grain surfaces and subsequently enter the gas phase through desorption. This presentation will discuss the enhanced gas-grain chemical model, UCLCHEM, which now features a one-dimensional aspect, and its application in interpreting iCOM detections within protostellar environments. It is evident that some iCOMs, like methanol, are generated farther from the core, while others, such as ethanol, are found closer. The second update emphasizes the suprathermal rotation of grains caused by their interaction with directional radiation or gas flow. This dynamic rotation induces centrifugal energy on a thinner icy surface, lowering the potential barrier for iCOMs and increasing the rate of desorption. Rapid rotation can also break thick ice layers into smaller pieces through centrifugal forces. As a result, these small fragments release iCOMs transiently during thermal spikes, whereas larger fragments can accelerate thermal sublimation more effectively than the original icy grains. These new non-thermal desorption mechanisms significantly impact the understanding of iCOM origins in star-forming regions and highlight the importance of considering the effect of suprathermal rotation of icy grains when using molecules to trace physical conditions in these areas.