across the slit to produce luminosity–weighted observed rotation curves along the slit.

Example rotation curves for a galaxy with $V_h=220$[kms$^{-1}$]{}, and inclination angle $i=60^{\circ}$, oriented along the slit, are provided in Figure \[fig:lbg\_rotationcurve\]. The curves from top to bottom represent: i) the NFW circular velocity profile along the major axis; ii) the luminosity-weighted rotation curve obtained by averaging across the slit, before convolution by the seeing; iii) the observed rotation curve in 0.5arcsec seeing; iv) the observed rotation curve in 0.9arcsec seeing. At a position 0.75arcsec along the slit, the measured rotation velocities are 0.85 and 0.62 of the NFW value on the major axis, for 0.5arcsec and 0.9arcsec seeing respectively.

![\[fig:lbg\_rotationcurve\]The effect of seeing on the measured rotation curve of a galaxy with halo velocity $V_h=220$[kms$^{-1}$]{}inclined at 60 degrees to the sky, with major–axis aligned with the spectroscopic slit.](./images/vcurve){width="0.85\columnwidth"}

To compare the model with the data we must reproduce the conditions by which the data were measured, as closely as possible. For a chosen scale radius $R_0$, we measured the rotation velocity at the (deprojected) radius $\beta R_0$, where the value of the constant $\beta$ was chosen to reproduce the average projected radius of the measured rotation curves. For 