Open AccessDark galaxies or tidal debris? Kinematical clues to the origin of massive isolated H i clouds
Author(s) -
Bekki Kenji,
Koribalski Bärbel S.,
Kilborn Virginia A.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society: letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.067
H-Index - 122
eISSN - 1745-3933
pISSN - 1745-3925
DOI - 10.1111/j.1745-3933.2005.00076.x
Subject(s) - physics , astrophysics , galaxy , dark matter , surface brightness , virgo cluster , debris , stars , tidal force , astronomy , dark galaxy , spiral galaxy , galaxy cluster , galaxy formation and evolution , disc galaxy , meteorology
An extended H i cloud (VIRGOH i 21) with an H i mass of ∼10 8 M ⊙ and no apparent optical counterpart was recently discovered in the Virgo cluster. In order to understand the origin of physical properties of apparently isolated H i clouds like VIRGOH i 21, we numerically investigate physical properties of tidal H i debris that were formed by galaxy–galaxy interactions in clusters of galaxies. Our hydrodynamical simulations demonstrate that tidal debris with total H i masses of 10 8 –10 9 M ⊙ can have (1) a wide spread of H i velocities (>200 km s −1 ) , (2) a small mass fraction of stars (∼10 per cent), and (3) a mean B ‐band surface brightness of the stellar components fainter than 30 mag arcsec −2 . These results suggest that VIRGOH i 21, which lies at a projected distance of ∼150 kpc from the one‐armed, H i ‐rich spiral galaxy M99 (NGC 4254), is tidal debris. We propose that the comparison between the simulated and the observed velocity fields of H i clouds allows us to better understand their nature and origin (e.g. whether they are just tidal debris or are ‘dark galaxies’ that have H i gas only and are embedded within dark matter haloes).