Universität zu Köln

Gaches, Brandt A. L., Bialy, Shmuel, Bisbas, Thomas G., Padovani, Marco, Seifried, Daniel and Walch, Stefanie (2022). Cosmic-ray-induced H-2 line emission Astrochemical modeling and implications for JWST observations. Astron. Astrophys., 664. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context. It has been proposed that H-2 near-infrared lines may be excited by cosmic rays and thus allow for a determination of the cosmic-ray ionization rate in dense gas. One-dimensional models show that measuring both the H-2 gas column density and H-2 line intensity enables a constraint on the cosmic-ray ionization rate as well as on the spectral slope of low-energy cosmic-ray protons in the interstellar medium. Aims. We aim to investigate the impact of certain assumptions regarding the H-2 chemical models and interstellar medium density distributions on the emission of cosmic-ray-induced H-2 emission lines. This is of particular importance for utilizing observations of these lines with the James Webb Space Telescope to constrain the cosmic-ray ionization rate. Methods. We compare the predicted emission from cosmic-ray-induced, rovibrationally excited H-2 emission lines for different one-and three-dimensional models with varying assumptions regarding the gas chemistry and density distribution. Results. We find that the model predictions of the H-2 line intensities for the (1-0)S(0), (1-0)Q(2), (1-0)O(2), and (1-0)O(4) transitions at 2.22, 2.41, 2.63, and 3.00 mu m, respectively, are relatively independent of the astro-chemical model and the gas density distribution when compared against the H-2 column density, making them robust tracers of the cosmic-ray ionization rate. Conclusions. We recommend the use of rovibrational H-2 line emission in combination with estimations of the cloud's H-2 column density to constrain the ionization rate and the spectrum of low-energy cosmic rays.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Gaches, Brandt A. L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bialy, Shmuel UNSPECIFIED UNSPECIFIED UNSPECIFIED Bisbas, Thomas G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Padovani, Marco UNSPECIFIED UNSPECIFIED UNSPECIFIED Seifried, Daniel UNSPECIFIED UNSPECIFIED UNSPECIFIED Walch, Stefanie UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-685167
DOI:	10.1051/0004-6361/202244090
Journal or Publication Title:	Astron. Astrophys.
Volume:	664
Date:	2022
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MOLECULAR CLOUDS; IONIZATION RATE; SILCC-ZOOM; IMPACT; CODE; CHEMISTRY; EVOLUTION; FRACTION; FLASH; CYCLE Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/68516