Deep 1.4 GHz Very Large Array Observations of the Radio Halo and Relic in Abell 2256
Deep 1.4 GHz Very Large Array Observations of the Radio Halo and Relic in Abell 2256
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DOI：
10.1086/504076
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发表时间：
2006-03
期刊：
影响因子：
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通讯作者：
T. Clarke;Torsten A. Ensslin Naval Research Laboratory;Interferometrics Inc.;M. F. Astrophysik
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文献类型：
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作者：
T. Clarke;Torsten A. Ensslin Naval Research Laboratory;Interferometrics Inc.;M. F. Astrophysik
我们给出了正在合并的星系团A2256的深度甚大阵列观测。众所周知，这个星系团在外围地区具有弥漫的陡谱射电残骸发射。我们的新观测提供了该星系团中央漫射电晕发射的第一张详细图像。射电晕在星团核心延伸超过800kpc，而遗迹辐射覆盖了∼1125kpc×520kpc的区域。射电遗迹的光谱指数图显示了从西北到发射东南边缘的光谱陡峭，整个遗迹的平均光谱指数在1369到1703兆赫之间，α=-1.2.偏振图显示，在遗迹区域，偏振分数高达45%，整个遗迹区域的平均偏振系数为20%。观测到的法拉第旋转量与银河系估计的旋转量是一致的，而且旋转量的离散度很小，这表明来自星系团内介质对遗迹的旋转量的贡献很小。我们使用遗迹的这些法拉第性质来论证它位于星系团的前侧。
We present deep Very Large Array observations of the merging galaxy cluster A2256. This cluster is known to possess diffuse steep-spectrum radio relic emission in the peripheral regions. Our new observations provide the first detailed image of the central diffuse radio halo emission in this cluster. The radio halo extends over more than 800 kpc in the cluster core, while the relic emission covers a region of ∼1125 kpc × 520 kpc. A spectral index map of the radio relic shows a spectral steepening from the northwest toward the southeast edge of the emission, with an average spectral index between 1369 and 1703 MHz of α = -1.2 across the relic. Polarization maps reveal high fractional polarization of up to 45% in the relic region with an average polarization of 20% across the relic region. The observed Faraday rotation measure is consistent with the Galactic estimate, and the dispersion in the rotation measure is small, suggesting that there is very little contribution to the rotation measure of the relic from the intracluster medium. We use these Faraday properties of the relic to argue that it is located on the front side of the cluster.