Open AccessA Dark Hydrogen Cloud in the Virgo Cluster
Author(s) -
Robert Minchin,
Jonathan S. Davies,
M. J. Disney,
P. J. Boyce,
D. A. Garcia,
C. A. Jordan,
V. A. Kilborn,
R. H. Lang,
Sarah C. M. Roberts,
S. Sabatini,
W. van Driel
Publication year - 2005
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/429538
Subject(s) - physics , astrophysics , solar mass , virgo cluster , dark matter , dark galaxy , galaxy , halo , astronomy , dark matter halo , surface brightness , sky , velocity dispersion , galaxy cluster
VIRGOHI21 is an HI source detected in the Virgo Cluster survey of Davies etal. (2004) which has a neutral hydrogen mass of 10^8 M_solar and a velocitywidth of Delta V_20 = 220 km/s. From the Tully-Fisher relation, a galaxy withthis velocity width would be expected to be 12th magnitude or brighter; howeverdeep CCD imaging has failed to turn up a counterpart down to asurface-brightness level of 27.5 B mag/sq. arcsec. The HI observations showthat it is extended over at least 16 kpc which, if the system is bound, givesit a minimum dynamical mass of ~10^11 M_solar and a mass to light ratio ofM_dyn/L_B > 500 M_solar/L_solar. If it is tidal debris then the putativeparents have vanished; the remaining viable explanation is that VIRGOHI21 is adark halo that does not contain the expected bright galaxy. This object wasfound because of the low column density limit of our survey, a limit much lowerthan that achieved by all-sky surveys such as HIPASS. Further such sensitivesurveys might turn up a significant number of the dark matter halos predictedby Dark Matter models.Comment: Accepted by ApJ
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