Collisions between galaxy clusters provide a test of the non-gravitational forces acting on dark matter. Dark matter's lack of deceleration in the `bullet cluster collision' constrained its self-interaction cross-section \sigma_DM/m < 1.25cm2/g (68% confidence limit) for long-ranged forces. Using the Chandra and Hubble Space Telescopes we have now observed 72 collisions, including both `major' and `minor' mergers. Combining these measurements statistically, we detect the existence of dark mass at 7.6\sigma significance. The position of the dark mass has remained closely aligned within 5.8+/-8.2 kpc of associated stars: implying a self-interaction cross-section \sigma_DM/m < 0.47 cm2/g (95% CL) and disfavoring some proposed extensions to the standard model.
@article{arxiv.1503.07675,
title = {The non-gravitational interactions of dark matter in colliding galaxy clusters},
author = {David Harvey and Richard Massey and Thomas Kitching and Andy Taylor and Eric Tittley},
journal= {arXiv preprint arXiv:1503.07675},
year = {2015}
}
Comments
5 Pages, 4 Figures and 18 pages supplementary information