Turbulence measurements from HI absorption spectra

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dc.creatorRoy, Nirupam
dc.creatorPeedikakkandy, Leshma
dc.creatorChengalur, Jayaram N.
dc.date2008-03-17
dc.date2008-05-13
dc.date.accessioned2026-07-07T09:42:20Z
dc.date.available2026-07-07T09:42:20Z
dc.descriptionWe use the millennium Arecibo 21 cm absorption-line survey measurements to examine the issue of the non-thermal contribution to the observed Galactic HI line widths. If we assume a simple, constant pressure model for the HI in the Galaxy, we find that the non-thermal contribution to the line width, v_{nt} scales as v^2_{nt} \propto l^α, for v_{nt} larger than \sim 0.7 km s^{-1}. Here l is a derived length scale and α\sim 0.7 \pm 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 line widths narrower than \sim 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 line width to determine corrected HI kinetic temperature. The new limits that we obtain imply that a significantly smaller (\sim 40% as opposed to 60%) fraction of the atomic interstellar medium in our Galaxy is in the warm neutral medium phase.
dc.description5 pages, 7 figures. Corrected typos. Accepted for publication in MNRAS Letters. The definitive version will be available at http://www.blackwell-synergy.com
dc.identifierhttps://arxiv.org/abs/0803.2511
dc.identifierhttp://arxiv.org/abs/0803.2511
dc.identifier2008, MNRAS, 387, L18
dc.identifierdoi:10.1111/j.1745-3933.2008.00473.x
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/162144
dc.subjectAstrophysics
dc.titleTurbulence measurements from HI absorption spectra
dc.typetext

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