Mon. Not. R. Astron. Soc., 403, 295-299 (2010/March-3)
HI in isolated extremely metal-deficient galaxies.
EKTA B. and CHENGALUR J.N.
Abstract (from CDS):
We present Giant Metrewave Radio Telescope Hi observations of two extremely metal-deficient (XMD) galaxies, UM133 and SDSSJ011914.27-093546.4, with no known nearby companions. Earlier Hi observations of XMD galaxies have shown that disturbed Hi morphologies and kinematics, generally related to tidal interaction with a companion, are common in them. However, some of these galaxies were already known to be in pairs before the Hi observations. The two galaxies studied here were specifically selected because they do not have any known nearby companions. None the less, we find that both the galaxies have highly disturbed Hi morphologies and velocity fields. These could have arisen from interactions with more distant companions than considered in our isolation criteria or merger with extremely gas-rich dwarf companions. It is also possible that distorted Hi distributions of these XMD galaxies are the result of cold gas accretion from the intergalactic medium. Our observations provide further support to the idea that inflow of metal-poor gas from the outskirts of a galaxy to the central star-forming regions (in the case of interaction), or cold gas accretion is the probable cause for the observed low emission-line metallicities of XMD galaxies.