  The interplay between dark matter (DM) and baryons has long been ignored when
building galaxies semi-empirically and observationally. Here I show that
baryonic gravity leads to an adiabatic contraction of DM halos, which is most
significant in massive galaxies. Ignoring this effect, the derived DM halos are
not guaranteed in dynamical equilibrium. I present a new approach to deriving
DM halos from rotation curves, which incorporates the adiabatic contraction.
The compressed halos turn out super cuspy with respect to NFW halos, which
require smaller baryonic contributions and less concentrated primordial halos.
I also examine the semi-empirical approach to building galaxies, and find the
adiabatic contraction can shift massive galaxies from the observed radial
acceleration relation dramatically. Both approaches lead to super cuspy DM
halos for massive galaxies, demonstrating the importance of the baryon-driven
contraction, which has to be taken into account in order to make an
apple-to-apple comparison with simulations.
