A merger shock in A2034

Matt S. Owers, Paul E J Nulsen, Warrick J. Couch, Cheng Jiun Ma, Laurence P. David, William R. Forman, Andrew M. Hopkins, Christine Jones, Reinout J. Van Weeren

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


We present a 250 ks Chandra observation of the cluster merger A2034 with the aim of understanding the nature of a sharp edge previously characterized as a cold front. The new data reveal that the edge is coherent over a larger opening angle and is significantly more bow-shock-shaped than previously thought. Within ∼27° about the axis of symmetry of the edge, the density, temperature, and pressure drop abruptly by factors of , , and , respectively. This is inconsistent with the pressure equilibrium expected of a cold front and we conclude that the edge is a shock front. We measure a Mach number and corresponding shock velocity v shock ≃ 2057 km s -1. Using spectra collected at the MMT with the Hectospec multi-object spectrograph, we identify 328 spectroscopically confirmed cluster members. Significantly, we find a local peak in the projected galaxy density associated with a bright cluster galaxy that is located just ahead of the nose of the shock. The data are consistent with a merger viewed within ∼23° of the plane of the sky. The merging subclusters are now moving apart along a north-south axis approximately 0.3 Gyr after a small impact parameter core passage. The gas core of the secondary subcluster, which was driving the shock, appears to have been disrupted by the merger. Without a driving "piston," we speculate that the shock is dying. Finally, we propose that the diffuse radio emission near the shock is due to the revival of pre-existing radio plasma that has been overrun by the shock.

Original languageEnglish
Article number163
Pages (from-to)1-13
Number of pages13
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 10 Jan 2014
Externally publishedYes


  • galaxies: clusters: individual (A2034)
  • X-rays: galaxies: clusters


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