  We describe and test a novel Dark Matter Annihilation Feedback (DMAF) scheme
that has been implemented into the well known cosmological simulation code
\textsf{GADGET-2}. In the models considered here, dark matter can undergo
self-annihilation/decay into radiation and baryons. These products deposit
energy into the surrounding gas particles and then the dark matter/baryon fluid
is self-consistently evolved under gravity and hydrodynamics. We present tests
of this new feedback implementation in the case of idealised dark matter halos
with gas components for a range of halo masses, concentrations and annihilation
rates. For some dark matter models, DMAF's ability to evacuate gas is enhanced
in lower mass, concentrated halos where the injected energy is comparable to
its gravitational binding energy. Therefore, we expect the strongest signs of
dark matter annihilation to imprint themselves onto the baryonic structure of
concentrated dwarf galaxies through their baryonic fraction and star formation
history. Finally we present preliminary results of the first self-consistent
DMAF cosmological box simulations showing that the small scale substructure is
washed out for large annihilation rates.
