EDP Sciences
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Volume 375, Number 1, August III 2001
Page(s) 219 - 226
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20010810

A&A 375, 219-226 (2001)
DOI: 10.1051/0004-6361:20010810

Status of HI searches for CHVCs beyond the Local Group

R. Braun1 and W. B. Burton2

1  Netherlands Foundation for Research in Astronomy, PO Box 2, 7990 AA Dwingeloo, The Netherlands
2  Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands

(Received 3 April 2000 / Accepted 5 June 2001 )

Growing evidence supports the suggestion that the compact high-velocity clouds of H I (CHVCs) are located throughout the Local Group and continue to fuel galactic evolution. Recent distance estimates to individual objects lie in the range 150-850 kpc, implying an H I mass range of $10^{5.7}\rightarrow10^{7.2} M_\odot$ together with sizes ranging from 2-12 kpc, while the average linewidth is 30 km s-1 FWHM. It is natural to ask whether objects of this type would not already have been seen by current blind H I surveys of the extragalactic sky. We consider the properties of the deepest published surveys of this type and conclude that the sensitivity and coverage have now begun to reveal the high mass end of the distribution ( $M_{\rm HI}> 10^{7} M_\odot$). Achieving detection limits an order of magnitude deeper should finally enable direct study of these systems beyond the Local Group, or definitively rule out their existence.

Key words: ISM: atoms -- ISM: clouds -- galaxy: evolution -- galaxy: formation -- galaxies: dwarf -- galaxies: Local Group

Offprint request: R. Braun, rbraun@nfra.nl

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