Galactic halos of self-interacting dark matter

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Recent, very accurate simulations of galaxy formation have revealed that the standard cold dark matter model has great difficulty in explaining the detailed structure of galaxies. One of the major problems is that galactic halos are too centrally concentrated. Dark matter self-interactions have been proposed as a possible means of resolving this inconsistency. Here, we investigate quantitatively the effect of dark matter self interactions on formation of galactic halos. Our numerical framework is extremely simple, while still keeping the essential physics. We confirm that strongly self-interacting dark matter leads to less centrally concentrated structures. Interestingly, we find that for a range of different interaction strengths, the dark matter halos are unstable to particle ejection on a timescale comparable to the Hubble time.