An Off-center Density Peak in the Milky Way's Dark Matter Halo?
  We show that the position of the central dark matter density peak may be
expected to differ from the dynamical center of the Galaxy by several hundred
parsec. In Eris, a high resolution cosmological hydrodynamics simulation of a
realistic Milky-Way-analog disk galaxy, this offset is 300 - 400 pc (~3
gravitational softening lengths) after z=1. In its dissipationless
dark-matter-only twin simulation ErisDark, as well as in the Via Lactea II and
GHalo simulations, the offset remains below one softening length for most of
its evolution. The growth of the DM offset coincides with a flattening of the
central DM density profile in Eris inwards of ~1 kpc, and the direction from
the dynamical center to the point of maximum DM density is correlated with the
orientation of the stellar bar, suggesting a bar-halo interaction as a possible
explanation. A dark matter density offset of several hundred parsec greatly
affects expectations of the dark matter annihilation signals from the Galactic
Center. It may also support a dark matter annihilation interpretation of recent
reports by Weniger (2012) and Su & Finkbeiner (2012) of highly significant 130
GeV gamma-ray line emission from a region 1.5 degrees (~200 parsec projected)
away from Sgr A* in the Galactic plane.
