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A Dark Hydrogen Cloud in the Virgo Cluster

Minchin, Robert, Davies, Jonathan Ivor, Disney, Michael John, Boyce, Peter, Garcia, Diego, Jordan, Christine, Kilborn, Virgina, Lang, Robert Hugh, Roberts, Sarah Georgina, Sabatini, Sabina and van Driel, Wim 2005. A Dark Hydrogen Cloud in the Virgo Cluster. The Astrophysical Journal 622 (1) , L21-24. 10.1086/429538

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VIRGOHI 21 is an H I source detected in the Virgo Cluster survey of Davies et al. that has a neutral hydrogen mass of 108 M and a velocity width of ?V20 = 220 km s-1. From the Tully-Fisher relation, a galaxy with this velocity width would be expected to be 12 mag or brighter; however, deep CCD imaging has failed to turn up a counterpart down to a surface brightness level of 27.5 B mag arcsec-2. The H I observations show that it is extended over at least 16 kpc, which, if the system is bound, gives it a minimum dynamical mass of ~1011 M and a mass-to-light ratio of Mdyn/LB > 500 M/L. If it is tidal debris, then the putative parents have vanished; the remaining viable explanation is that VIRGOHI 21 is a dark halo that does not contain the expected bright galaxy. This object was found because of the low column density limit of our survey, a limit much lower than that achieved by all sky H I surveys such as those carried out at Parkes and Jodrell Bank. Further such sensitive surveys might turn up a significant number of the dark matter halos predicted by galaxy formation models.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Uncontrolled Keywords: Dark matter ; Galaxies: clusters: individual (Virgo); galaxies: General ; Radio lines: galaxies
ISSN: 0004-6256
Last Modified: 04 Jun 2017 01:41

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