  We utilize Young's algorithm to model the adiabatic compression of the dark
matter haloes of galaxies in the THINGS survey to determine the relationship
between the halo fit to the rotation curve and the corresponding primordial
halo prior to compression. Young's algorithm conserves radial action and
angular momentum, resulting in less halo compression than more widely utilized
approximations. We find that estimates of the parameters of the NFW haloes fit
to the current dark matter distribution systematically overestimate the
concentration and underestimate the virial velocity of the corresponding
primordial halo. It is the latter that is predicted by dark matter simulations;
so accounting for compression is a necessary step for evaluating whether
massive galaxies are consistent with dark matter-only simulations. The inferred
primordial haloes broadly follow the c-V200 relation expected in a LCDM
cosmogony, but often scatter to lower concentrations. We are unable to obtain
fits at all for those galaxies whose current dark matter haloes are poorly
described by the NFW form. We thus find a mixed bag: some galaxies are
reasonably well described by adiabatic compression within a primordial NFW
halo, while others require additional mechanisms that reduce the density of
dark matter below the primordial initial condition.
