We present H i 21cm emission observations of the z \sim 0.00632 sub-damped Lyman- \alpha absorber ( sub-DLA ) towards PG 1216+069 made using the Arecibo Telescope and the Very Large Array ( VLA ) .
The Arecibo H i 21cm spectrum corresponds to an H i mass of \sim 3.2 \times 10 ^ { 7 } M _ { \odot } , two orders of magnitude smaller than that of a typical spiral galaxy .
This is surprising since in the local Universe the cross-section for absorption at high H i column densities is expected to be dominated by spirals .
The H i 21cm emission detected in the VLA spectral cube has a low signal-to-noise ratio , and represents only half the total flux seen at Arecibo .
Emission from three other sources is detected in the VLA observations , with only one of these sources having an optical counterpart .
This group of H i sources appears to be part of complex “ W ” , believed to lie in the background of the Virgo cluster .
While several H i cloud complexes have been found in and around the Virgo cluster , it is unclear whether the ram pressure and galaxy harassment processes that are believed to be responsible for the creation of such clouds in a cluster environment are relevant at the location of this cloud complex .
The extremely low metallicity of the gas , \sim 1 / 40 -solar , also makes it unlikely that the sub-DLA consists of material that has been stripped from a galaxy .
Thus , while our results have significantly improved our understanding of the host of this sub-DLA , the origin of the gas cloud remains a mystery .