Chemical differentiation between star-forming regions - The Orion Hot Core and Compact Ridge

Abstract

A dynamical-chemical model of mass star-forming regions, in which gas and dust grains are included, is presented. Consideration is given to the last 100,000 yr of the accretion phase of a protostellar object embedded in a dense and massive cloud with a density and temperature gradient. The gas and grain chemical evolution of two collapsing shells of this cloud is traced, until the end of the protostar accretion phase, at which time the density no longer increases. It is found that differences in thermal history during the gravitational collapse of the two circumstellar shells can lead to chemical differentiation between the Orion Hot Core and Compact Ridge. Detailed comparison between the present model results and observations of these two sources exhibits a mixed pattern of agreement and disagreement.