Evolution of dark matter microhalos through stellar encounters
  In the cold dark matter scenario, the smallest dark matter halos may be earth
mass or smaller. These microhalos would be the densest dark matter objects in
the Universe, making their accurate characterization important for
astrophysical dark matter detection efforts. Moreover, their properties are
closely linked to the nature of dark matter and the physics of the early
universe, making them valuable cosmological probes. Dark matter microhalos
survive as subhalos within larger galactic halos, but due to their small size,
they are susceptible to encounters with individual stars. We use a large number
of $N$-body simulations to develop a framework that can predict the evolution
of a microhalo's density profile due to stellar encounters. We find that there
is a universal density profile for microhalos subjected to stellar encounters,
and each encounter alters a microhalo's scale parameters in a way that is
simply related to the energy the encounter injects. Our framework can rapidly
and accurately characterize the impact of stellar encounters on whole ensembles
of microhalos, making it a promising tool for understanding the populations of
microhalos within galactic halos.
