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Intergalactic HI Clouds

Published online by Cambridge University Press:  26 May 2016

F. H. Briggs*
Affiliation:
RSAA, Mount Stromlo Observatory, ANU Cotter Road, Weston Creek 2611 ACT, Australia

Abstract

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Neutral intergalactic clouds are so greatly out numbered by galaxies that their integral HI content is negligible in comparison to that contained in optically luminous galaxies. In fact, no HI cloud that is not associated with a galaxy or grouping of galaxies has yet been identified. This points to a causal relationship that relies on gravitational potentials that bind galaxies also being responsible for confining HI clouds to sufficient density that they can become self-shielding to the ionizing background radiation. Unconfined clouds of low density become ionized, but confined clouds find themselves vulnerable to instability and collapse, leading to star formation.

Type
Part 1. Census
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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