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Abstract Self-interactions of dark matter (DM) particles can potentially lead to an observable separation between the DM halo and the stars of a galaxy moving through a region of large DM density. Such a separation has recently been observed in a galaxy falling into the core of the galaxy cluster Abell 3827. We estimated the DM self-interaction cross-section needed to reproduce the observed effects and find that the sensitivity of Abell 3827 has been significantly overestimated in a previous study. Our corrected estimate is /m ₃₌ 3\, cm²\, g^-1 when self-interactions result in an effective drag force and σ/mDM ∼ 1. 5 cm2 g−1 for the case of contact interactions, in some tension with previous upper bounds.
Kahlhoefer et al. (Fri,) studied this question.