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Observational Signatures of Cosmic-Ray Interactions in Molecular Clouds

Owen, ER; On, AYL; Lai, S-P; Wu, K; (2021) Observational Signatures of Cosmic-Ray Interactions in Molecular Clouds. The Astrophysical Journal , 913 (1) , Article 52. 10.3847/1538-4357/abee1a. Green open access

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Abstract

We investigate ionization and heating of gas in the dense, shielded clumps/cores of molecular clouds bathed by an influx of energetic, charged cosmic rays (CRs). These molecular clouds have complex structures, with substantial variation in their physical properties over a wide range of length scales. The propagation and distribution of CRs is thus regulated accordingly, in particular, by the magnetic fields threaded through the clouds and into the dense regions within. We have found that a specific heating rate reaching 10−26 erg cm−3 s−1 can be sustained in the dense clumps/cores for Galactic environments, and this rate increases with CR energy density. The propagation of CRs and heating rates in some star-forming filaments identified in IC 5146 are calculated, with the CR diffusion coefficients in these structures determined from magnetic field fluctuations inferred from optical and near-infrared polarizations of starlight, which is presumably a magnetic field tracer. Our calculations indicate that CR heating can vary by nearly three orders of magnitude between different filaments within a cloud due to different levels of CR penetration. The CR ionization rate among these filaments is similar. The equilibrium temperature that could be maintained by CR heating alone is of order 1 K in a Galactic environment, but this value would be higher in strongly star-forming environments, thus causing an increase in the Jeans mass of their molecular clouds.

Type: Article
Title: Observational Signatures of Cosmic-Ray Interactions in Molecular Clouds
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-4357/abee1a
Publisher version: http://doi.org/10.3847/1538-4357/abee1a
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10128806
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