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Durham University

Department of Physics

Staff profile

Publication details for Prof Richard Massey

Robertson, A., Massey, R., Eke, V. & Bower, R. (2015). Self-interacting dark matter scattering rates through cosmic time. Monthly Notices of the Royal Astronomical Society 453(3): 2267-2276.

Author(s) from Durham


We estimate the rate of dark matter scattering in collapsed structures throughout the history of the Universe. If the scattering cross-section is velocity independent, then the canonical picture is correct that scatterings occur mainly at late times. The scattering rate peaks slightly at redshift z ∼ 6, and remains significant today. Half the scatterings occur after z ∼ 1, in structures more massive than 1012 M⊙. Within a factor of 2, these numbers are robust to changes in the assumed astrophysics, and the scatterings would be captured in cosmological simulations. However, for particle physics models with a velocity-dependent cross-section (as for Yukawa potential interactions via a massive mediator), the scattering rate peaks before z ∼ 20, in objects with mass ≲104 M⊙. These precise values are sensitive to the redshift-dependent mass–concentration relation and the small-scale cut-off in the matter power spectrum. In extreme cases, the qualitative effect of early interactions may be reminiscent of warm dark matter and strongly affect the subsequent growth of structure. However, these scatterings are being missed in existing cosmological simulations with limited mass resolution.