High-resolution analysis of cold and hot dark matter in cosmic string wakes

Abstract

We study the accretion of cold and hot dark matter onto a cosmic string wake using a high-resolution numerical simulation. We verify previous analytical calculations predicting the radius of bound matter around wakes and inflow velocities of the dark matter, as well as assumptions about the self-similarity of the solution. In cold wakes, we show that self-similarity is approached quickly after a `binding' transition. Hot wakes approach self-similarity rapidly once the free streaming `pressure' falls below a critical value and accretion begins. We also analytically calculate the size of the overdensity in wakes with cold dark matter and compare the results to simulations. We remark that the results derived may be used in testing gravitational numerical codes in the non-linear regime.