Do We Need to Know the Temperature in Prestellar Cores?

Abstract

Molecular line observations of starless (prestellar) cores combined with a chemical evolution modeling and radiative transfer calculations are a powerful tool to study the earliest stages of star formation. However, conclusions drawn from such a modeling may noticeably depend on the assumed thermal structure of the cores. The assumption of isothermality, which may work well in chemo-dynamical studies, becomes a critical factor in molecular line formation simulations. We argue that even small temperature variations, which are likely to exist in starless cores, can have a nonnegligible effect on the interpretation of molecular line data and derived core properties. In particular, "chemically pristine" isothermal cores (low depletion) can have centrally peaked C18O and C34S radial intensity profiles, while having ringlike intensity distributions in models with a colder center and/or warmer envelope assuming the same underlying chemical structure. Therefore, derived molecular abundances based on oversimplified thermal models may lead to a misinterpretation of the line data.