Does dark matter interact with itself? Whole classes of particle models could be ruled out if astronomers could provide a definitive answer to this question---and this is a question that can only be answered with astrophysical methods. As demonstrated by the famous Bullet Cluster, merging galaxy clusters may provide a way to answer this question, but so far we have only large upper limits. I will describe efforts by the Merging Cluster Collaboration to extend the merging-cluster technique to a larger sample of clusters to improve the self-interaction upper limit by an order of magnitude. I will describe how we find merging systems with favorable properties, how we are increasing our understanding of those systems with a spectroscopic and weak lensing survey, and our efforts to model those systems. Initial results show that we are able to efficiently select for massive systems with merger axes mostly in the plane of the sky, and to put reasonable constraints on the merger velocity. However, much work remains before we obtain a dark matter constraint, and we may end up learning more about the fascinating astrophysics of cluster mergers than about dark matter.
2015 October 08, 15:00
Observatório Astronómico de Lisboa (Seminar room)
Tapada da Ajuda, 1349-018 Lisboa