Investigating the effects of chemistry on molecular line profiles of infalling low mass cores
arXiv:1007.1093 · doi:10.1111/j.1365-2966.2010.17296.x
Abstract
We have coupled a chemical model with two dynamical models of collapsing low mass star-forming cores to predict abundances across the core of the commonly used infall tracers, CS and HCO, at various stages of the collapse. The models investigated are a new ambipolar diffusion model and the `inside-out' collapse model. We have then used these results as an input to a radiative transfer model to predict the line profiles of several transitions of these molecules. For the inside-out collapse model, we predict significant molecular depletion due to freeze-out in the core centre, which prevents the formation of the blue asymmetry (believed to be the `signature' of infall) in the line profiles. Molecular depletion also occurs in the ambipolar diffusion model during the late stages of collapse, but the line profiles still exhibit a strong blue asymmetry due to extended infall. For the inside-out collapse model to exhibit the blue asymmetry it is necessary to impose a negative kinetic temperature gradient on the core and suppress freeze-out. Since freeze-out is observed in several class 0 protostars which are thought to be collapsing, this presents a major inconsistency in the inside-out collapse model of star formation.
18 pages, 17 figures, accepted for publication in MNRAS
References in corpus (6)
- Evolutionary Signatures in the Formation of Low-Mass Protostars. II. Towards Reconciling Models and Observations
- Microscopic simulation of methanol and formaldehyde ice formation in cold dense cores
- Desorption From Interstellar Ices
- The Ionization Fraction of Barnard 68: Implications for Star and Planet Formation
- Molecular line profiles as diagnostics of protostellar collapse: modelling the `blue asymmetry' in inside-out infall
- The Evolution of Density Structure of Starless and Protostellar Cores