We present X-ray and weak lensing observations of the merging cluster system 1E0657 556. Due to the recently collision of a merging subcluster with the main cluster, the X-ray plasma has been displaced from the cluster galaxies in both components. The weak lensing data shows that the lensing surface potential is in spatial agreement with the galaxies (˜10% of the observed baryons) and not with the X-ray plasma (˜90% of the observed baryons). We argue that this shows that regardless of the form of the gravitational force law at these large distances and low accelerations, these observations require that the majority of the mass of the system be some form of unseen matter.
Nuclear Physics B Proceedings Supplements
- Pub Date:
- November 2007
- 4 pages, 1 figure, to appear in the proceedings of the 2006 UCLA Dark Matter Symposium. Accompanying the paper is a partial data release at http://flamingos.astro.ufl.edu/1e0657/index.html