A Direct Empirical Proof of the Existence of Dark Matter

We present new weak lensing observations of 1E0657-558 (z=0.296), a uniquecluster merger, that enable a direct detection of dark matter, independent ofassumptions regarding the nature of the gravitational force law. Due to thecollision of two clusters, the dissipationless stellar component and thefluid-like X-ray emitting plasma are spatially segregated. By using bothwide-field ground based images and HST/ACS images of the cluster cores, wecreate gravitational lensing maps which show that the gravitational potentialdoes not trace the plasma distribution, the dominant baryonic mass component,but rather approximately traces the distribution of galaxies. An 8-sigmasignificance spatial offset of the center of the total mass from the center ofthe baryonic mass peaks cannot be explained with an alteration of thegravitational force law, and thus proves that the majority of the matter in thesystem is unseen.Comment: Accepted for publication in ApJ