2008/03/31 by Nirupam Roy, Leshma Peedikakkandy, Jayaram N. Chengalur · 1 citation
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1111/j.1745-3933.2008.00473.x
published as 2008, MNRAS, 387, L18 · 5 pages, 7 figures. Corrected typos. Accepted for publication in MNRAS Letters. The definitive version will be available at http://www.blackwell-synergy.com
openalex publication_date 2008/04/08 · arxiv created 2008/05/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Abstract We use the millennium Arecibo 21-cm absorption-line survey measurements to examine the issue of the non-thermal contribution to the observed Galactic H i linewidths. If we assume a simple, constant pressure model for the H i in the Galaxy, we find that the non-thermal contribution to the linewidth, vnt scales as v2nt∝lα, for vnt larger than ∼0.7 km s−1. Here, l is a derived length-scale and α ∼ 0.7 ± 0.1. This is consistent with what one would expect from a turbulent medium with a Kolmogorov scaling. Such a scaling is also predicted by theoretical models and numerical simulations of turbulence in a magnetized medium. For non-thermal linewidths narrower than ∼0.7 km s−1, this scaling breaks down, and we find that the likely reason is ambiguities arising from Gaussian decomposition of intrinsically narrow, blended lines. We use the above estimate of the non-thermal contribution to the linewidth to determine corrected H i kinetic temperature. The new limits that we obtain imply that a significantly smaller (∼40 per cent as opposed to 60 per cent) fraction of the atomic interstellar medium in our Galaxy is in the warm neutral medium phase.