this case the average mass will be lower and the range of masses will be larger. This conclusion finds some support in the recent clustering analysis of Adelberger et al. (2005): by matching the clustering strength, and space density to the corresponding quantities for haloes in an n–body simulation they derive a median halo mass of $10^{11.86\pm0.3}$[${\mathrm M_{\odot}\thinspace}$]{}. Our analysis suggests lower masses still. Our result appears to be more consistent with the predicted masses of the collisional starburst model of SPF, which has a median halo mass of $10^{11.3}$[${\mathrm M_{\odot}\thinspace}$]{}. The picture that emerges is one which leaves some of the most–massive haloes available for occupation by other populations which do not meet the LBG selection criteria.

These conclusions rest on the analysis of a small number of rotation curves of low signal–to–noise, without the benefit of complementary high–resolution imaging. Recently Erb et al. (2004) have questioned whether the majority of LBGs are dynamically relaxed, which would undermine the basis of our calculation. In an attempt to maximise the chances of measuring rotation, they used HST imaging of a sample of galaxies at $z\sim 2$ to select the fraction with morphologies consistent with the expectation for edge-on disks. They 