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Estimating the kinetic temperature from H I 21-cm absorption studies: correction for turbulence broadening

Koley, Atanu and Roy, Nirupam (2019) Estimating the kinetic temperature from H I 21-cm absorption studies: correction for turbulence broadening. In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 483 (1). pp. 593-598.

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Official URL: http://dx.doi.org/10.1093/mnras/sty3152

Abstract

The neutral hydrogen 21-cm transition is a useful tracer of the neutral interstellar medium. However, it is often not straightforward to infer physical conditions from the observed 21-cm absorption and/or emission spectra. One complication when estimating the temperature of the atomic gas is that the linewidth can have a significant contribution from non-thermal broadening. Here, we propose a formalism to separate the thermal and non-thermal broadening using a self-consistent model of turbulence broadening of the HI 21-cm absorption components. By applying this novel method, we have estimated the spin and the kinetic temperature of diffuse Galactic neutral hydrogen, and we have found that a large fraction of gas has a temperature in the unstable range. The turbulence is found to be subsonic or transonic in nature, and the clouds seem to have a bimodal size distribution. Assuming that the turbulence is magnetohydrodynamic in nature, the estimated magnetic field strength is of mu G order, and is found to be uncorrelated with the H I number density.

Item Type: Journal Article
Additional Information: copyright for this article belongs to OXFORD UNIV PRESS
Keywords: turbulence; ISM: atoms; ISM: general; ISM: structure; radio lines: ISM
Department/Centre: Division of Physical & Mathematical Sciences > Joint Astronomy Programme
Division of Physical & Mathematical Sciences > Physics
Depositing User: Id for Latest eprints
Date Deposited: 15 Jul 2019 10:25
Last Modified: 15 Jul 2019 10:25
URI: http://eprints.iisc.ac.in/id/eprint/62298

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