Investigating the effects of chemistry on molecular line profiles of infalling low mass cores

• Published in: arXiv.org
• Main Authors: Roberts, Julia F, Stace, Hugh A W, Rawlings, Jonathan M C
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 07.07.2010
• Subjects: Ambipolar diffusion; Astrochemistry; Asymmetry; Depletion; Low mass stars; Mathematical models; Organic chemistry; Physics - Solar and Stellar Astrophysics; Protostars; Radiative transfer; Star & galaxy formation; Star formation; Temperature gradients; Tracers
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1007.1093

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.