Cusp-to-core conversion in galaxies from late-time dark matter oscillations

by Matteo Puel (McGill University)

The reason why dwarf spheroidal and other galaxies appear to have a lower central density than predicted from N-body simulations based on LCDM cosmology is still an open question. Apart from the possibility that baryonic physics could play a leading role in shaping the inner density profile of galaxies, the most popular new-physics explanation is to assume heat transfer caused by dark matter (DM) self-interactions. In this talk, I will present a novel mechanism of solving the core-cusp problem through reactivation of DM annihilation in galaxies at late times. This can happen in asymmetric DM models when there is a very small DM-number violating mass term that causes oscillations between DM and its antiparticle. Using analytical as well as N-body galactic simulations, we show that this mechanism can convert cuspy DM profiles into cored ones for light fermionic DM with mass in the range (0.1 - 1) GeV and a lighter mediator into which the DM can annihilate. I identify regions of the parameter space where annihilation of DM particles is more efficient than elastic scattering at reducing the inner density of the DM profile. DM annihilation is therefore a qualitatively distinct alternative to the mechanism of elastic self-interacting DM for addressing the core-cusp problem.