the two curves.](./images/PLOT_mmw_comparison){width="0.85\columnwidth"}

Figure \[fig:lbg\_mmwdistribution\] plots the cumulative PDF of the velocity widths (corrected for instrumental resolution) of the 32 LBGs (thick stepped line), taken from table 1, Paper I. For the seven galaxies with spatially resolved velocity profiles, $\sigma$ was measured from the central line profile.

Also plotted in Figure \[fig:lbg\_mmwdistribution\] is the MMW prediction for the distribution of halo circular velocities at a radius of 7kpc (thin stepped line). This was calculated starting with the distribution of halo velocities at the virial radius $V_h$ from figure 4 of MMW. For the NFW profile, the conversion to circular velocity at radius R is $$\Big(\frac{V_{c \rm R}}{V_h}\Big)^2=\frac{1}{x}\frac{\ln(1+cx)-(cx)/(1+cx)}
{\ln(1+c)-c/(1+c)},$$ where $x=R/R_h$. We use the relation $R_h=V_h/(10H(z))$ and we assume concentration $c=4$. These are the circular velocities computed ignoring the effects of baryonic dissipation, which will raise the circular velocities. This increase is probably substantial but is difficult to predict reliably. The simple adiabatic contraction model (Mo, Mao & White 1998) indicates that the circular velocities $V_{c7}$ could increase by a factor of about 1.5, but the detailed processes involved in baryonic contraction are poorly understood. There is both theoretical (El-Zant, Shlosman, & Hoffman 2001) and observational (Binney & Evans 2001) evidence 