Discovery of a dissociative galaxy cluster merger with large physical separation

William A. Dawson, David Wittman, M. James Jee, Perry Gee, John P. Hughes, J. Anthony Tyson, Samuel Schmidt, Paul Thorman, Maruša Bradač, Satoshi Miyazaki, Brian Lemaux, Yousuke Utsumi, Vera E. Margoniner

Research output: Contribution to journalArticlepeer-review

112 Citations (Scopus)


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 ≲ 7cm2 g-1. The system is observed at least 0.7 ± 0.2Gyr since first pass-through, thus providing a picture of cluster mergers 2-5times 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.

Original languageEnglish
Article numberL42
JournalAstrophysical Journal Letters
Issue number2
Publication statusPublished - 2012 Mar 10

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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