GIANT LOBES OF CENTAURUS A RADIO GALAXY OBSERVED WITH THE SUZAKU X-RAY SATELLITE-猫眼课题宝

DOI：

10.1088/0004-637x/766/1/48

发表时间：

2012-10

期刊：

The Astrophysical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

Ł. Stawarz;Yasuyuki T. Tanaka;G. Madejski;Shane O'Sullivan;C. Cheung;C. Cheung;I. Feain;Y. Fukazawa;P. Gandhi;M. Hardcastle;Jun Kataoka;M. Ostrowski;B. Reville;A. Siemiginowska;A. Simionescu;Tadayuki Takahashi;Y. Takei;Y. Takeuchi;Norbert Werner

我们报告朱雀观测选定的区域内的射电星系半人马座A的南巨瓣。在我们的分析中，我们专注于在0.5-10 keV范围内用X射线成像光谱仪检测到的不同X射线特征，其中一些可能与最近高质量的无线电强度和偏振图所揭示的叶的精细结构有关。利用现有的光子统计数据，我们发现探测到的X射线特征的光谱特性与温度kT > 1 keV的热气体的热发射或光子指数为Γ = 2.0 ± 0.5的幂律辐射连续谱同样一致。然而，这些不同的模型所暗示的等离子体参数有利于分析X射线斑点的同步加速器起源，表明在半人马座A的巨大结构内发生了高达1000 TeV能量的电子非常有效的加速，尽管只有在与扩展和高度极化的无线电灯丝相关的孤立和紧凑的区域中。我们还提出了一个详细的分析弥漫的X射线发射填充整个视野的仪器，从而在一个软过剩的组件最适合的温度为kT <$0.5千电子伏的热模型的试探性检测。观测到的过剩的确切来源仍然不确定，尽管能量方面的考虑指向充满了大部分体积的瓣体的热气体，并与非热等离子体混合，而不是涉及膨胀的射电结构边缘周围的热星系际介质凝结的替代方案。如果正确的话，这将是第一次在X射线中探测到射电星系扩展叶的热含量。在这种情况下，热气体的相应数密度为ng 10−4 cm−3，而其压强似乎与由无线电发射电子和波瓣磁场提供的体积平均非热压强几乎完全均分。银河系前景辐射的一个显著的大尺度波动，导致过量的前景X射线辐射与叶对齐，不能排除。虽然是试探性的，但我们的发现可能意味着活动星系中扩展叶的结构可能是高度不均匀和不均匀的，磁重联和湍流加速过程不断将磁能转化为等离子体粒子的内能，导致等离子体β参数在体积平均平衡条件β 1附近可能发生显着的空间和时间变化。

We report on Suzaku observations of selected regions within the southern giant lobe of the radio galaxy Centaurus A. In our analysis we focus on distinct X-ray features detected with the X-ray Imaging Spectrometer within the range 0.5–10 keV, some of which are likely associated with fine structure of the lobe revealed by recent high-quality radio intensity and polarization maps. With the available photon statistics, we find that the spectral properties of the detected X-ray features are equally consistent with thermal emission from hot gas with temperatures kT > 1 keV, or with a power-law radiation continuum characterized by photon indices Γ ∼ 2.0 ± 0.5. 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 up to ≳ 10 TeV energies is taking place within the giant structure of Centaurus A, albeit only in isolated and compact regions associated with extended and highly polarized radio filaments. We also present a detailed analysis of the diffuse X-ray emission filling the whole field of view of the instrument, resulting in a tentative detection of a soft excess component best fitted by a thermal model with a temperature of kT ∼ 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, rather than to the alternative scenario involving a condensation of the hot intergalactic medium around the edges of the expanding radio structure. If correct, this would be the first detection of the thermal content of the extended lobes of a radio galaxy in X-rays. The corresponding number density of the thermal gas in such a case is ng ∼ 10−4 cm−3, while its pressure appears to be in almost exact equipartition with the volume-averaged non-thermal pressure provided by the radio-emitting electrons and the lobes’ magnetic field. A prominent large-scale fluctuation of the Galactic foreground emission, resulting in excess foreground X-ray emission aligned with the lobe, cannot be ruled out. Although tentative, our findings potentially imply that the structure of the extended lobes in active galaxies is likely to be highly inhomogeneous and non-uniform, with magnetic reconnection and turbulent acceleration processes continuously converting magnetic energy to internal energy of the plasma particles, leading to possibly significant spatial and temporal variations in the plasma β parameter around the volume-averaged equilibrium condition β ∼ 1.

GIANT LOBES OF CENTAURUS A RADIO GALAXY OBSERVED WITH THE SUZAKU X-RAY SATELLITE

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