The local dark matter distribution in self-interacting dark matter halos

We study the effects of dark matter self-interactions on the local dark matter distribution in selected Milky Way-like galaxies in the EAGLE hydrodynamical simulations. The simulations were run with two different self-interacting dark matter models, a constant and velocity-dependent self-interaction cross-section. We find that the local dark matter velocity distribution of the Milky Way-like halos in the simulations with dark matter self -interactions and baryons are generally similar to those extracted from cold collisionless dark matter simulations with baryons. In both cases, the local dark matter speed distributions agree well with their best fit Maxwellian distributions. Including baryons in the simulations with or without dark matter self-interactions increases the local dark matter density and shifts the dark matter speed distributions to higher speeds. To study the implications for direct detection, we compute the dark matter halo integrals obtained directly from the simulations and compare them to those obtained from the best fit Maxwellian velocity distribution. We find that a Maxwellian distribution provides a good fit to the halo integrals of most halos, without any significant difference between the results of different dark matter self -interaction models.

Automated summary

We investigate the impact of dark matter self-interactions on the local distribution of dark matter in selected Milky Way-like galaxies. Two different self-interacting dark matter models, with constant and velocity-dependent self-interaction cross-sections, are employed in hydrodynamical simulations. The results show that adding self-interactions and baryons in the simulations leads to local velocity distributions of dark matter halos resembling those obtained from simulations with cold collisionless dark matter and baryons. The best fit Maxwellian distributions fit well with the local dark matter speed distributions in both cases. Inclusion of baryons increases the local dark matter density and shifts the dark matter speed distributions to higher speeds. Considering the implications for direct detection, the halo integrals obtained directly from the simulations are compared to those derived from the best fit Maxwellian velocity distribution, with the majority of halos showing good agreement with the Maxwellian distribution regardless of the dark matter self-interaction models.