  A strong correlation has been measured between the observed centripetal
accelerations in galaxies and the accelerations implied by the baryonic
components of galaxies. This empirical radial acceleration relation must be
accounted for in any viable model of galaxy formation. We measure and compare
the radial accelerations contributed by baryons and by dark matter in disk
galaxies in the MassiveBlack-II hydrodynamic galaxy formation simulation. The
sample of 1594 galaxies spans three orders of magnitude in luminosity and four
in surface brightness, comparable to the observed sample from the Spitzer
Photometry & Accurate Rotation Curves (SPARC) dataset used by McGaugh et al.
(2016). We find that radial accelerations contributed by baryonic matter only
and by total matter are highly correlated, with only small scatter around their
mean or median relation, despite the wide ranges of galaxy luminosity and
surface brightness. We further find that the radial acceleration relation in
this simulation differs from that of the SPARC sample, and can be described by
a simple power law in the acceleration range we are probing.
