  We present an analysis of the effects of dissipational baryonic physics on
the local dark matter (DM) distribution at the location of the Sun, with an
emphasis on the consequences for direct detection experiments. Our work is
based on a comparative analysis of two cosmological simulations of a Milky Way
halo: Eris, a full hydrodynamic simulation, and ErisDark, its DM-only
realization. We find that two distinct processes lead in Eris to a 30%
enhancement of DM in the disk plane at the location of the Sun: the accretion
and disruption of satellites resulting in a DM component with net angular
momentum and the contraction of baryons pulling DM into the disk plane without
forcing it to co-rotate. Owing to its particularly quiescent merger history for
dark halos of Milky Way mass, the co-rotating dark disk in Eris is less massive
than what has been suggested by previous work, contributing only 9% of the
local DM density. The speed distribution in Eris is broadened and shifted to
higher speeds compared to its DM-only twin simulation ErisDark. At high speeds
$f(v)$ falls more steeply in Eris than in ErisDark or the SHM, easing the
tension between recent results from the CDMS-II and XENON100 experiments. The
non-Maxwellian aspects of $f(v)$ are still present, but much less pronounced in
Eris than in DM-only runs. The weak dark disk increases the time-averaged
scattering rate by only a few percent at low recoil energies. On the high
velocity tail, however, the increase in typical speeds due to baryonic
contraction results in strongly enhanced mean scattering rates compared to
ErisDark, although they are still suppressed compared to the SHM. Similar
trends are seen regarding the amplitude of the annual modulation, while the
modulated fraction is increased compared to the SHM and decreased compared to
ErisDark.
