We present Australia Telescope Compact Array ( ATCA ) observations of a galaxy-sized intergalactic HI cloud ( “ the Vela Cloud ” ) in the NGC 3256 galaxy group .
The group contains the prominent merging galaxy NGC 3256 , which is surrounded by a number of HI fragments , the tidally disturbed galaxy NGC 3263 , and several other peculiar galaxies .
The Vela Cloud , with an HI mass of 3-5 \times 10 ^ { 9 } \cal M _ { \odot } , resides southeast of NGC 3256 and west of NGC 3263 , within an area of 9′ \times 16′ ( 100 kpc \times 175 kpc for an adopted distance of 38 Mpc ) .
In our ATCA data the Vela Cloud appears as 3 diffuse components and contains 4 density enhancements .
The Vela Cloud ’ s properties , together with its group environment , suggest that it has a tidal origin .
Each density enhancement contains \sim 10 ^ { 8 } \cal M _ { \odot } of HI gas which is sufficient material for the formation of globular cluster progenitors .
However , if we represent the enhancements as Bonnor-Ebert spheres , then the pressure of the surrounding HI would need to increase by at least a factor of 6 in order to cause the collapse of an enhancement .
Thus we do not expect them to form massive bound stellar systems like super star clusters or tidal dwarf galaxies .
Since the HI density enhancements have some properties in common with High Velocity Clouds , we explore whether they may evolve to be identified with these starless clouds instead .