由法拉第旋转测量后发座星系团的磁场
The Coma cluster magnetic field from Faraday rotation measures
摘要：
通过法拉第旋转测量（RM）图像与数值模拟的磁场的比较，对后发座团簇的磁场强度、径向分布和功率谱进行了研究。本文分析了用甚大阵在3.6，6和20厘米观测的后发座星系团场中七个射电源的偏振数据，导出了具有千秒差距尺度分辨率的法拉第旋转测度。随机三维磁场模型已经模拟了不同的中心强度B_0和径向幂律斜率eta值，其中eta表示场如何与气体密度分布成比例。我们得出的中心磁场强度，和径向剖面值，最好地再现RM的意见。我们发现，磁场功率谱是很好地表示的Kolmogorov功率谱的最小规模~ 2 kpc和最大规模~ 34 kpc。中心磁场强度和径向斜率被限制在（B_0=3.9 microG; eta=0.4）和（B_0=5.4 microG; eta=0.7）的范围内，在1 σ内。观测和模拟之间的最佳协议是实现为B_0=4.7 microG; eta=0.5。B_0>7 microG和<3 microG以及eta 1.0的值< 0.2 and eta >在99%置信水平下与RM数据不一致。
英文摘要：
The aim of the present work is to constrain the Coma cluster magnetic field strength, its radial profile and power spectrum by comparing Faraday Rotation Measure (RM) images with numerical simulations of the magnetic field. We have analyzed polarization data for seven radio sources in the Coma cluster field observed with the Very Large Array at 3.6, 6 and 20 cm, and derived Faraday Rotation Measures with kiloparsec scale resolution. Random three dimensional magnetic field models have been simulated for various values of the central intensity B_0 and radial power-law slope eta, where eta indicates how the field scales with respect to the gas density profile. We derive the central magnetic field strength, and radial profile values that best reproduce the RM observations. We find that the magnetic field power spectrum is well represented by a Kolmogorov power spectrum with minimum scale ~ 2 kpc and maximum scale ~ 34 kpc. The central magnetic field strength and radial slope are constrained to be in the range (B_0=3.9 microG; eta=0.4) and (B_0=5.4 microG; eta=0.7) within 1sigma. The best agreement between observations and simulations is achieved for B_0=4.7 microG; eta=0.5. Values of B_0>7 microG and <3 microG as well as eta < 0.2 and eta > 1.0 are incompatible with RM data at 99 % confidence level.
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