EPoS Contribution

Molecular lines in prestellar cores: what should we take into account when we deal with line profiles?

Yaroslav Pavlyuchenkov
ax-Planck-Institut für Astronomie, Heidelberg, Germany

Nowadays, molecular line observations represent a common method to probe physical conditions inside prestellar cores and protoplanetary disks. Such observations contain information not only about temperature and density but also about the chemical structure and gas kinematics in these objects and therefore can be used to infer the chemical age and evolutionary status of the cores. However, this information is well hidden in molecular line profiles and cannot be easily extracted.

In this contribution we illustrate various factors which affect molecular line profile formation and which should taken into account when interpreting observations of prestellar cores. The key factors responsible for the emergent line profile are the distributions of temperature, density, molecular abundances, and velocity. The molecular abundances depend, in turn, on a number of factors, which are not directly related to dynamics of the cloud. Among these factors are: the initial chemical composition, external UV field, cosmic ray intensity. Also, we have to take into account uncertainties of the chemical reaction rates and problems with line radiative transfer simulations for a turbulent medium. We illustrate the effect of the mentioned factors using step-by-step improvement of the prestellar core model. Starting with a static isothermal chemically uniform 1D model we put more and more physics into the model to see how it affects molecular line profiles. As a conclusion, we state that all the discussed factors are comparable and therefore are important if we are interested to model and interpret molecular line observations of prestellar cores.