GMRT observations of interstellar clouds in the 21cm line of atomic hydrogen |
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| Authors: | Rekhesh Mohan K S Dwarakanath G Srinivasan Jayaram N Chengalur |
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| Institution: | (1) Raman Research Institute, 560 080 Bangalore, India;(2) National Center for Radio Astrophysics, Ganeshkhind, 411 007 Pune, India |
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| Abstract: | Nearby interstellar clouds with high (|ν|≥10km s−1) random velocities although easily detected in NaI and CaII lines have hitherto not been detected (in emission or absorption)
in the HI 21cm line. We describe here deep Giant Metrewave Radio Telescope (GMRT) HI absorption observations toward radio
sources with small angular separation from bright O and B stars whose spectra reveal the presence of intervening high random
velocity CaII absorbing clouds. In 5 out of the 14 directions searched we detect HI 21cm absorption features from these clouds.
The mean optical depth of these detections is ∼0.09 and FWHM is ∼10km s−1, consistent with absorption arising from CNM clouds. |
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| Keywords: | ISM: clouds kinematics and dynamics Radio lines: ISM |
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