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Excitation temperature of the warm neutral medium as a new probe of the Lyα radiation field


Murray, CE and Lindner, RR and Stanimirovic, S and Goss, WM and Heiles, C and Dickey, J and Pingel, NM and Lawrence, A and Jencson, J and Babler, BL and Hennebelle, P, Excitation temperature of the warm neutral medium as a new probe of the Lyα radiation field, Astrophysical Journal Letters, 781, (2) Article L41. ISSN 2041-8205 (2014) [Refereed Article]

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Copyright 2014 The American Astronomical Society

DOI: doi:10.1088/2041-8205/781/2/L41


We use the Karl G. Jansky Very Large Array to conduct a high-sensitivity survey of neutral hydrogen (HI) absorption in the Milky Way. In combination with corresponding HI emission spectra obtained mostly with the Arecibo Observatory, we detect a widespread warm neutral medium component with excitation temperature (Ts) = 7200+1800-1200 K (68% confidence). This temperature lies above theoretical predictions based on collisional excitation alone, implying that Lya scattering, the most probable additional source of excitation, is more important in the interstellar medium (ISM) than previously assumed. Our results demonstrate that HI absorption can be used to constrain the Lya radiation field, a critical quantity for studying the energy balance in the ISM and intergalactic medium yet notoriously difficult to model because of its complicated radiative transfer, in and around galaxies nearby and at high redshift.

Item Details

Item Type:Refereed Article
Keywords:ISM: clouds;ISM: structure
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Dickey, J (Professor John Dickey)
ID Code:89255
Year Published:2014
Web of Science® Times Cited:19
Deposited By:Mathematics and Physics
Deposited On:2014-02-27
Last Modified:2022-08-31

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