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Astrophysics Luncheon Seminar

Evidence for Self-interacting Dark Matter: A Call for a Regime Change
Presented by Will Dawson -- Host: Julian Merten
University of California Davis

Monday, April 8, 2013
12:00 noon in 169-336

Abstract
DLSCL J0916.2+2951 (Musket Ball Cluster) is a galaxy cluster merger where the dark matter and galaxies have become dissociated from the collisional gas. Because the time since first pass-through is longer than for any other such merger, this system is the one most sensitive to a nonzero dark matter self-interaction cross-section, which would be observed as the dark matter trailing the collisionless galaxies. We detect an offset of 19" between the weak lensing mass centroid and the galaxy density centroid consistent with expectations of a dark matter cross-section between 0.2 and 1.0 cm^2/g. We are able to rule out the hypothesis of a zero dark matter cross-section at ~85% confidence. In addition to discussing this measurement I will introduce a new regime of dark matter constraint with merging clusters. In the past, constraints have been determined in an ad hoc cluster-by-cluster basis without estimate of uncertainty. I will discuss the present efforts of the Merging Cluster Collaboration to systematically create and analyze a sample of dissociative cluster mergers capable of either measuring the dark matter self-interaction cross-section (at the 3-σ level) or constraining it to such a degree that self-interacting dark matter becomes astrophysically uninteresting (σDM<0.1 cm2/g).


SVCP Astrophysics


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