of $V_r/\sigma$ of the seven galaxies. We found that a value $\alpha(obs)=\sqrt{2}$ (motivated by the isothermal sphere model) provided a satisfactory fit. This value of $\alpha(obs)$ then converts the distribution of the 32 values of $\sigma$, assumed representative of the population, to the distribution of $V_{c7}$ for LBGs. We compared this against the, larger, required value of $\alpha(req)=2.6$ that would be needed to reconcile the measured distribution of $\sigma$ with the distribution of $V_{c7}$ predicted by the massive–halo model. The small value of $\alpha(obs)$ was inconsistent with the required value of $\alpha(req)$, implying halo virial masses an order of magnitude smaller than the predictions of the massive–halo model.

Our previous analysis made a number of simplifying assumptions. In computing $\alpha(obs)$ we took no account of the effect of atmospheric seeing, which would blur the light from the bright, baryon dominated centres of the galaxies to the faint outer parts, smoothing the transition from $+$ve to $-$ve velocity in the rotation curve, such that the rotation velocity would be underestimated. The data we analysed were taken in average conditions of 0.5arcsec seeing, and the rotation velocities were measured at an average offset of 0.64arcsec. Erb et al. (2004) give an indication 