Giant Lobes of Centaurus A Radio Galaxy Observed with the Suzaku X-ray Satellite
L. Stawarz, Y. T. Tanaka, G. Madejski, S. P. O'Sullivan, C. C. Cheung, I. J. Feain, Y. Fukazawa, P. Gandhi, M. J. Hardcastle, J. Kataoka, M. Ostrowski, B. Revil… 展开作者
L. Stawarz, Y. T. Tanaka, G. Madejski, S. P. O'Sullivan, C. C. Cheung, I. J. Feain, Y. Fukazawa, P. Gandhi, M. J. Hardcastle, J. Kataoka, M. Ostrowski, B. Reville, A. Siemiginowska, A. Simionescu, T. Takahashi, Y. Takei, Y. Takeuchi, N. Werner
[abridged] We report on Suzaku observations of selected regions within the Southern giant lobe of the radio galaxy Centaurus A. We focus on distinct X-ray features likely associated with fine radio structure of the lobe. We find that the spectral properties of the detected X-ray features are equally consistent with thermal emission from hot gas, or with a power-law radiation continuum. However, the plasma parameters implied by these different models favor a synchrotron origin for the analyzed X-ray spots, indicating that a very efficient acceleration of electrons is taking place within the giant structure of Centaurus A, albeit only in isolated and compact regions. We also present a detailed analysis of the diffuse X-ray emission, resulting in a tentative detection of a soft excess component best fitted by a thermal model with a temperature of 0.5 keV. The exact origin of the observed excess remains uncertain, although energetic considerations point to thermal gas filling the bulk of the volume of the lobe and mixed with the non-thermal plasma. The corresponding pressure of the thermal gas in such a case appears to be in almost exact equipartition with the pressure provided by the radio-emitting electrons and the magnetic field. Although tentative, our findings potentially imply that the structure of the extended lobes in active galaxies is likely to be highly inhomogeneous, with magnetic reconnection processes continuously converting magnetic energy to internal energy of the plasma particles, leading to spatial and temporal variations in the plasma parameters around the equilibrium condition.
The energetics of giant radio galaxy lobes from inverse Compton scattering observations
巨射电星系（GRG）叶是研究粒子演化和B场能量学的极好实验室。然而，这些结果是基于假设的形状和扩展的GRG波瓣电子光谱。我们重新检查GRG瓣的能量学，通过RG瓣中的相对论电子对CMB光子的逆康普顿散射（ICS-CMB）来评估RG瓣的物理条件，它们的能量学和它们的辐射制度。我们认为GRG DA 240最近观察到的朱雀作为一个参考案例，我们也讨论了其他RG叶观察钱德拉和XMM。利用从射电到伽玛射线的多频信息，对DA 240东瓣的能量分布进行了建模，得到了对电子能谱形状和扩展的约束。我们使用无线电和X射线数据来约束电子光谱的形状和归一化，然后计算对总电子能量密度敏感的GRG瓣中预期的SZ效应。我们表明，由X射线观测得到的电子能量密度U_e仅比实际值有一个粗略的下限，而且考虑到较低的电子动量p_1的实际估计，大多数基于X射线测量的U_e估计值都必须增加一个很大的因子。这使得RG波瓣远离均分条件，朝向粒子主导和康普顿功率主导的状态。我们使用RG波瓣在U_e/U_B与U_e/U_CMB平面上的分布作为RG波瓣中粒子和场主导以及辐射机制主导的不同物理状态之间的进一步划分。我们的结论是，在RG叶中观察到的ICS-CMB机制产生的SZ效应提供了可靠的p_1和U_e的估计，是确定RG叶的总能量密度和评估其物理状态的最佳工具。
