Open AccessMassive H i clouds with no optical counterparts as high‐density regions of intragroup H i rings and arcs
Author(s) -
Bekki K.,
Koribalski B. S.,
Ryder S. D.,
Couch W. J.
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.1745-3933.2005.08625.x
Subject(s) - physics , astrophysics , galaxy , ring (chemistry) , star formation , surface brightness , intergalactic travel , arc (geometry) , galaxy group , galaxy formation and evolution , geometry , chemistry , mathematics , organic chemistry , redshift
We present a new scenario in which massive intragroup H i clouds are the high‐density parts of large H i rings/arcs formed by dynamical interaction between galaxy groups and gas‐rich, low surface brightness (LSB) galaxies with extended gas discs. Our hydrodynamical simulations demonstrate that the group tidal field is very efficient at stripping the outer H i gas of the disc if the gaseous disc of the LSB galaxy extends 2–5 times further than the stellar disc. We find that a massive, extended ‘leading stream’ orbiting the centre of the group can form out of the stripped outer H i envelope, while the severely shrunken LSB galaxy, whose stellar disc remains unaffected, continues on its path. The result is a relatively isolated, massive H i cloud with a ring‐ or arc‐like shape, a very inhomogeneous density distribution ( N H i ∼ 1.0 × 10 17 –1.1 × 10 20 atom cm −2 ) , and, initially, no stellar content. Only the high‐density peaks of the simulated intragroup H i ring/arc can be detected in many current H i observations. These will appear as relatively isolated ‘H i islands’ near the group centre. We also find that star formation can occur within the ring/arc, if the total gas mass within the intragroup ring/arc is very large (∼4 × 10 9 M ⊙ ) . We discuss these results in terms of existing observations of intragroup gas (e.g. the Leo Ring and HIPASS J0731–69) and intergalactic H ii regions.