Mapping the allowed parameter space for decaying dark matter models

I consider constraints on a phenomenological decaying dark matter model, in which two weakly interacting massive particle species have a small mass splitting, and in which the heavier particle decays to the lighter particle and a massless particle on cosmological time scales. The decay parameter space is parametrized by vk, the speed of the lighter particle in the center-of-mass frame of the heavier particle prior to decay, and the decay time . Since I consider the case in which dark matter halos have formed before there has been significant decay, I focus on the effects of decay on already formed halos. I show that the vk parameter space may be constrained by observed properties of dark matter halos. I highlight which set of observations is likely to yield the cleanest constraints on vk parameter space, and calculate the constraints in those cases in which the effect of decay on the observables can be calculated without N-body simulations of decaying dark matter. I show that for vk * 5 10 km s , the z 1⁄4 0 galaxy cluster mass function and halo mass-concentration relation constrain * 40 Gyr, and that precise constraints on for smaller vk will require N-body simulations.