论文标题
极化同步加速器从波动 - dynamo动作发射的属性 - I.应用于星系簇
Properties of polarized synchrotron emission from fluctuation-dynamo action -- I. Application to galaxy clusters
论文作者
论文摘要
使用波动发电机的磁水动力学模拟，我们执行宽带的合成观测值，以研究极化同步子发射的特性以及法拉第旋转在推断星系簇的膨胀培养基（ICM）中极化结构中所起的作用。在发电机的饱和状态下，我们找到了法拉第深度（FD）分散$σ_ {\ rm fd} \大约100 $ rad m $^{ - 2} $，与ICM中观察到的值一致。值得注意的是，FD功率谱在质量上类似于$ m（k）/k $，其中$ m（k）$是磁性频谱，而$ k $ the vavenumber。但是，当FD通过将RM合成应用于ICM的偏振发射时，由于分辨率差和FD空间中的频谱复杂性，该相似性在高$ K $中被打破。与FD获得的高斯概率分布函数（PDF）不同，同步加速器强度的PDF是对数正常的。 ICM中相对较大的$σ_ {\ rm fd} $引起了低频下像素均值和峰值偏振强度的强频依赖性变化（$ \ sillesim 1.5 \，{\ rm ghz} $）。在模拟分辨率下获得的平均分数偏振$ \ langle p \ rangle $从0.5 GHz的$ <0.1 $增加到其内在值为$ \ sim0.3 $ 6 GHz。光束平滑显着影响$ \ lyssim 1.5 \，{\ rm ghz} $的极化属性，将$ \ langle p \ rangle $降低到$ \ lyseSim 0.01 $ 0.5 GHz。在频率$ \ gtrsim 5 \，{\ rm ghz} $上，即使使用RM合成恢复时，极化仍然不受影响。因此，我们的结果强调了对高频（$ \ gtrsim 5 \，{\ rm ghz} $）观测值的需求，以未来的射电望远镜有效探测ICM中极化发射的性质。
Using magnetohydrodynamic simulations of fluctuation dynamos, we perform broad-bandwidth synthetic observations to investigate the properties of polarized synchrotron emission and the role that Faraday rotation plays in inferring the polarized structures in the intracluster medium (ICM) of galaxy clusters. In the saturated state of the dynamo, we find a Faraday depth (FD) dispersion $σ_{\rm FD} \approx 100$ rad m$^{-2}$, in agreement with observed values in the ICM. Remarkably, the FD power spectrum is qualitatively similar to $M(k)/k$, where $M(k)$ is the magnetic spectrum and $k$ the wavenumber. However, this similarity is broken at high $k$ when FD is obtained by applying RM synthesis to polarized emission from the ICM due to poor resolution and complexities of spectrum in FD space. Unlike the Gaussian probability distribution function (PDF) obtained for FD, the PDF of the synchrotron intensity is lognormal. A relatively large $σ_{\rm FD}$ in the ICM gives rise to strong frequency-dependent variations of the pixel-wise mean and peak polarized intensities at low frequencies ($\lesssim 1.5\,{\rm GHz}$). The mean fractional polarization $\langle p \rangle$ obtained at the resolution of the simulations increases from $<0.1$ at 0.5 GHz to its intrinsic value of $\sim0.3$ at 6 GHz. Beam smoothing significantly affects the polarization properties below $\lesssim 1.5\,{\rm GHz}$, reducing $\langle p \rangle$ to $\lesssim 0.01$ at 0.5 GHz. At frequencies $\gtrsim 5\,{\rm GHz}$, polarization remains largely unaffected, even when recovered using RM synthesis. Thus, our results underline the need for high-frequency ($\gtrsim 5\,{\rm GHz}$) observations with future radio telescopes to effectively probe the properties of polarized emission in the ICM.
