Ionized gas towards galactic centre - Constraints from low-frequency recombination lines

Anantharamaiah, K. R. ; Bhattacharya, D. (1986) Ionized gas towards galactic centre - Constraints from low-frequency recombination lines Journal of Astrophysics and Astronomy, 7 (3). pp. 141-153. ISSN 0250-6335

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Observations of the H272α recombination line towards the galactic centre show features near VLSR= 0, -50 and + 36 kms-1. We have combined the parameters of these features with the available H166α measurements to obtain the properties of the ionized gas present along the line of sight and also in the '3 kpc arm'. For the line-of-sight ionized gas we get an electron density around 7 cm-3 and a pathlength through it ~ 10-60 pc. The emission measure and the electron temperature are in the range 500-2900 pc cm-6 and 2000-6000 K. respectively. The ionized gas in the 3 kpc arm has an electron density of 30 cm-3 and extends over 9 pc along the line of sight if we assume an electron temperature of 104 K. Using the available upper limit to the intensity of the H351α recombination line, we show that the distributed ionized gas responsible for the dispersion of pulsar signals should have a temperature > 4500 K. and a minimum filling factor of 20 per cent. We also show that recombination lines from the 'warm ionized' gas proposed by McKee & Ostriker (1977) should be detectable in the frequency range 100-150 MHz towards the galactic centre with the sensitivity available at present.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Galactic Centre; Recombination Lines-galaxy; 3 kpc Arm-interstellar Medium; Distributed Ionized Gas
ID Code:27957
Deposited On:15 Dec 2010 12:41
Last Modified:17 May 2016 11:09

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