Discovery of a Dissociative Galaxy Cluster Merger with Large Physical Separation
Bradač, Maruša; Hughes, John P.; Dawson, William A.; Tyson, J. Anthony; Miyazaki, Satoshi; Utsumi, Yousuke; Jee, M. James; Lemaux, Brian; Wittman, David; Gee, Perry; Schmidt, Samuel; Thorman, Paul; Margoniner, Vera E.
United States, Japan
Abstract
We present DLSCL J0916.2+2951 (z = 0.53), a newly discovered major cluster merger in which the collisional cluster gas has become dissociated from the collisionless galaxies and dark matter (DM). We identified the cluster using optical and weak-lensing observations as part of the Deep Lens Survey. Our follow-up observations with Keck, Subaru, Hubble Space Telescope, and Chandra show that the cluster is a dissociative merger and constrain the DM self-interaction cross-section σDM m -1 DM <~ 7 cm2 g-1. The system is observed at least 0.7 ± 0.2 Gyr since first pass-through, thus providing a picture of cluster mergers 2-5 times further progressed than similar systems observed to date. This improved temporal leverage has implications for our understanding of merging clusters and their impact on galaxy evolution.