A study of neutral hydrogen in five small galaxy groups |
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Authors: | D. G. Barnes R. L. Webster |
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Affiliation: | Astrophysics and Supercomputing, Swinburne University of Technology, Mail 31, PO Box 218, Hawthorn, VIC 3122, Australia;School of Physics, University of Melbourne, VIC 3010, Australia |
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Abstract: | High-resolution H i imaging observations of a heterogeneous sample of small galaxy groups are presented. The five galaxy groups studied show a broad range of individual H i properties: e.g. loose groups surrounding LGG 138 and the genuinely compact LGG 455 are identified; a massive ring of neutral gas is discovered encircling two luminous galaxies in the LGG 138 group; a galaxy-sized mass of H i is found in LGG 455 confined to an extragalactic cloud which exceeds the threshold density for star formation, yet is optically invisible; and the CCG 1 group is argued to be a chance alignment of Centaurus cluster galaxies. Global results of the study are that the deficit of H i flux in synthesis imaging data compared with single-dish data is put forward as a quantitative measure of the diffuseness of neutral gas in galaxy groups; several groups contain gas-poor galaxies that ordinarily would contain detectable quantities of H i – this is interpreted as being caused by an increased chance of gas-sweeping collisions in the group environment; and some evidence is found to support previous findings that compact groups preferentially occur in loose systems. |
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Keywords: | galaxies: evolution galaxies: interactions radio lines: galaxies |
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