论文标题
巨型射线银河NGC 6251的低频观察
Low-frequency observations of the Giant Radio Galaxy NGC 6251
论文作者
论文摘要
我们在150 MHz的边界周期/FRII巨人宽度Galaxy NGC 6251中进行了洛法的观察。本文呈现了NGC 6251最敏感和最高分辨率的图像，迄今为止，这些频率呈现出来，这首次揭示了首次与北湖的低面积扩展，并可能与北湖较低的后流相关联。 NGC 6251组件的集成光谱与以前的测量较高的频率相一致，类似于附近射电星系的其他LOFAR研究的结果。我们发现NGC 6251的外部结构是在平气处或略微电子主导的，类似于Frii源而不是Fris。但是，由于与几何形状和X射线测量值相关的不确定性，该结论仍然是暂定的，以确定外叶尺度上的外部压力分布。我们对北叶的扩展年龄和$ t \ gtrsim 250 $ Myr和$ t \ gtrsim 210 $ MYR的后流进行了下限。我们介绍了NGC 6251中的150 MHz极化的首次检测。利用Lofar的高度解决方案，我们在$ b <0.2（λ_b / 10 {\ rm kpc}^$ b <0.2（λ_b / 10 {\ rm kpc}）组中，磁场上的磁场上限为$ $ $ $ $ $ $ gm $ lm <60 $λ_b= 240 $ kpc。
We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest-resolution images of NGC 6251 at these frequencies to date, revealing for the first time a low-surface-brightness extension to the northern lobe, and a possible backflow associated with the southern lobe. The integrated spectra of components of NGC 6251 are consistent with previous measurements at higher frequencies, similar to results from other LOFAR studies of nearby radio galaxies. We find the outer structures of NGC 6251 to be either at equipartition or slightly electron dominated, similar to those of FRII sources rather than FRIs; but this conclusion remains tentative because of uncertainties associated with the geometry and the extrapolation of X-ray measurements to determine the external pressure distribution on the scale of the outer lobes. We place lower limits on the ages of the extension of the northern lobe and the backflow of the southern lobe of $t \gtrsim 250$ Myr and $t \gtrsim 210$ Myr respectively. We present the first detection of polarisation at 150 MHz in NGC 6251. Taking advantage of the high Faraday resolution of LOFAR, we place an upper limit on the magnetic field in the group of $B < 0.2 (Λ_B / 10 {\rm kpc})^{-0.5} μ$G for a coherence scale of $Λ_B < 60 {\rm kpc}$ and $B < 13 μ$G for $Λ_B = 240$ kpc.
