We present a weak-lensing analysis for a merging galaxy cluster, CIZA J2242.8+5301, which hosts double radio relics, using three-b and Subaru/Suprime-Cam imaging (Br′z′). Since the lifetime of dark matter halos colliding into clusters is longer than that of X-ray emitting gas halos, weak-lensing analysis is a powerful method to constrain merger dynamics. Two-dimensional shear fitting using a clean background catalog suggests that the cluster undergoes a merger with a mass ratio of about 2: 1. The main halo is located around the gas core in the southern region, while no concentrated gas core is associated with the northern sub-halo. We find that the projected cluster mass distribution resulting from an unequal-mass merger is in excellent agreement with the curved shapes of the two radio relics and the overall X-ray morphology, except for the lack of the northern gas core. The lack of a prominent radio halo enables us to constrain an upper limit of the fractional energy of magnetohydrodynamic turbulence of (δ B/B)2< O(10-6) at a resonant wavenumber, by finding a balance between the acceleration time and the time after the core passage or the cooling time, with an assumption of resonant acceleration by a second-order Fermi process.
CITATION STYLE
Okabe, N., Akamatsu, H., Kakuwa, J., Fujita, Y., Zhang, Y., Tanaka, M., & Umetsu, K. (2015). Radio relics tracing the projected mass distribution in CIZA J2242.8+5301. Publications of the Astronomical Society of Japan, 67(6). https://doi.org/10.1093/pasj/psv085
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