Gamma-ray Signal from Earth-mass Dark Matter Microhalos
  Earth-mass dark matter microhalos with size of ~100 AUs are the first
structures formed in the universe, if the dark matter of the Universe are made
of neutralino. Here, we report the results of ultra-high-resolution simulations
of the formation and evolution of these microhalos. We found that microhalos
have the central density cusps of the form $\rho \propto r^{-1.5}$, much
steeper than the cusps of larger dark halos. The central regions of these
microhalos survive the encounters with stars except in very inner region of the
galaxy down to the radius of a few hundreds pcs from the galactic center. The
annihilation signals from nearest microhalos are observed as gamma-ray
point-sources (radius less than 1'), with unusually large proper motions of
~0.2 degree per year. Their surface brightnesses are ~10% of that of the
galactic center. Their S/N ratios might be better if they are far from the
galactic plane. Luminosities of subhalos are determined only by their mass, and
they are more than one order of magnitude luminous than the estimation by
Springel et al. (2008): A boost factor can be larger than 1000. Perturbations
to the millisecond pulsars by gravitational attractions of nearby earth-mass
microhalos can be detected by the observations of Parkes Pulsar Timing Array
(PPTA).
