Telescope limits on cool H I in galaxy groups
نویسندگان
چکیده
We present Giant Metrewave Radio Telescope 21-cm HI observations towards a sample of compact radio sources behind galaxy groups, to search for cool HI. The results – from high dynamic range spectra for 8 lines-of-sight through 7 galaxy groups – do not show any evidence for absorption by cool HI. At a resolution of 20 km s −1 , the optical depth upper limits obtained were between 0.0075 and 0.035 (3σ); these correspond to upper limits of a few times 10 23 m −2 for the column density of any cool HI along these lines of sight (assuming a spin temperature of 100 K).
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