Heating the dark matter halo with dark radiation from supernovae

Abstract

Supernova explosions are among the most extreme events in the Universe, making them a promising environment in which to search for the effects of light, weakly coupled new particles. As significant sources of energy, they are known to have an important effect on the dynamics of ordinary matter in their host galaxies but their potential impact on the dark matter (DM) halo remains less explored. In this work, we investigate the possibility that some fraction of the supernova energy is released via the form of dark radiation into the DM halo. Based on evaluation of energetics, we find that even a small fraction of the total SN energy is sufficient to change the overall shape of the DM halo and transform a cuspy halo into a cored one. This may help to explain the cores that are observed in some dwarf galaxies. Alternatively, one can interpret the upper limit on the size of a possible DM core as an upper limit on the energy that can go into light particles beyond the SM. These arguments are largely independent of a concrete model for the new physics. Nevertheless, it is important to ensure that the conditions we need, i.e.~significant supernova emissivity of dark radiation and the opacity of DM halo to the dark radiation, can be met in actual models. To demonstrate this, we study four simple benchmark models: the dark photon, dark Higgs, and gauged $B-L$ and $L_\mu - L_\tau$ models -- all provide light weakly coupled particles serving as the dark radiation. Assuming a sizable coupling of the dark radiation to DM, we find that all of the benchmark models have a significant part of the parameter space that meets the conditions. Interestingly, the couplings allowed by observations of SN1987A can have a significant effect on the halo of dwarf spheroidal galaxies.