Anantharamaiah, KR and Bhattacharya, D (1986) Ionized Gas towards Galactic Centre-Constraints from Low-Frequency Recombination Lines. In: Journal of Astrophysics & Astronomy, 7 (3). 141 -153.
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Observations of the H272Î± 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 -166 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 - 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 H351Î± recombination line, we show that the distributed ionized gas responsible for the dispersion of pulsar signals should have a temperature > 4500 - 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:||Journal Article|
|Additional Information:||Copyright of this article belongs to Indian Academy of Sciences.|
|Keywords:||galactic centre;recombination lines-Galaxy;3 kpc arminterstellar medium;distributed ionized gas.|
|Department/Centre:||Division of Physical & Mathematical Sciences > Physics|
|Date Deposited:||27 Aug 2009 04:39|
|Last Modified:||19 Sep 2010 05:35|
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