CF$^+$ excitation in the interstellar medium
Abstract
The detection of CF in interstellar clouds potentially allows astronomers to infer the elemental fluorine abundance and the ionization fraction in ultraviolet-illuminated molecular gas. Because local thermodynamic equilibrium (LTE) conditions are hardly fulfilled in the interstellar medium (ISM), the accurate determination of the CF abundance requires one to model its non-LTE excitation via both radiative and collisional processes. Here, we report quantum calculations of rate coefficients for the rotational excitation of CF in collisions with para- and ortho-H2 (for temperatures up to 150 K). As an application, we present non-LTE excitation models that reveal population inversion in physical conditions typical of ISM photodissociation regions (PDRs). We successfully applied these models to fit the CF emission lines previously observed toward the Orion Bar and Horsehead PDRs. The radiative transfer models achieved with these new rate coefficients allow the use of CF as a powerful probe to study molecular clouds exposed to strong stellar radiation fields.
Cite
@article{arxiv.2012.02027,
title = {CF$^+$ excitation in the interstellar medium},
author = {Benjamin Desrousseaux and François Lique and Javier R. Goicoechea and Ernesto Quintas-Sánchez and Richard Dawes},
journal= {arXiv preprint arXiv:2012.02027},
year = {2021}
}