A Dark Hydrogen Cloud in the Virgo Cluster
Abstract
VIRGOHI21 is an HI source detected in the Virgo Cluster survey of Davies et al. (2004) which has a neutral hydrogen mass of 10^8 M_solar and a velocity width of Delta V_20 = 220 km/s. From the Tully-Fisher relation, a galaxy with this velocity width would be expected to be 12th magnitude or brighter; however deep CCD imaging has failed to turn up a counterpart down to a surface-brightness level of 27.5 B mag/sq. arcsec. The HI observations show that it is extended over at least 16 kpc which, if the system is bound, gives it a minimum dynamical mass of ~10^11 M_solar and a mass to light ratio of M_dyn/L_B > 500 M_solar/L_solar. If it is tidal debris then the putative parents have vanished; the remaining viable explanation is that VIRGOHI21 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 surveys such as HIPASS. Further such sensitive surveys might turn up a significant number of the dark matter halos predicted by Dark Matter models.
Keywords
Cite
@article{arxiv.astro-ph/0502312,
title = {A Dark Hydrogen Cloud in the Virgo Cluster},
author = {Robert Minchin and Jonathan Davies and Michael Disney and Peter Boyce and Diego Garcia and Christine Jordan and Virginia Kilborn and Robert Lang and Sarah Roberts and Sabina Sabatini and Wim van Driel},
journal= {arXiv preprint arXiv:astro-ph/0502312},
year = {2009}
}
Comments
Accepted by ApJL