SBS 0335-052 and its companion 0335-052W are shown to be a unique pair of currently forming dwarf galaxies associated with a huge HI cloud (Izotov et al. 1997, Lipovetsky et al. 1997, Thuan et al. 1997, Pustilnik et al. 1997). We present the analysis of the velocity field of this HI cloud, obtained with the VLA, and the model of its rotation curve to derive the total mass distribution in this system. We argue that this gas cloud is rotationally supported in the gravitational potential of a massive DM halo, and discuss the implications of this fact for galaxy formation and evolution scenarios. This unique system apparently preserves the original unperturbed structure of its DM halo and is thus very valuable to confront halo properties with model predictions. The parameters of the DM halo and neutral gas set limits, based on observational evidence, to the range of physical conditions under which a pristine hydrogen cloud can survive as a stable object over cosmlogical time scales. We discuss the possible effect of the massive spiral galaxy at the projected distance of about 100/h kpc to these forming galaxies.
IAU Joint Discussion
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