High-energy particle acceleration at the radio-lobe shock of Centaurus A
High-energy particle acceleration at the radio-lobe shock of Centaurus A
复制标题
半人马座 A 射电瓣激波的高能粒子加速
DOI：
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
K. Woodley
中科院分区：
文献类型：
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作者：
J. Croston;R. Kraft;M. Hardcastle;M. Birkinshaw;D. Worrall;P. Nulsen;R. Penna;G. Sivakoff;A. Jordán;N. Brassington;D. Evans;W. Forman;M. Gilfanov;J. Goodger;W. Harris;C. Jones;A. Juett;S. Murray;Somak Raychaudhury;C. Sarazin;R. Voss;K. Woodley
我们提出了新的结果，使用Chandra超大型计划观测数据（740 ks总观测时间）的西南射电瓣的半人马座A周围的冲击。辐射的X射线谱在叶的西南边缘外的周围可以用一个单一的幂律模型来描述，而银河系的吸收-热模型则非常不受欢迎，除了最靠近核的区域。我们的结论是，一个显着的分数的X射线辐射周围的西南部的瓣是同步加速器，而不是热。我们推断，在该地区的冲击是最强的和周围的气体密度最低，膨胀的瓣加速粒子的X射线同步hrotron发射能量，类似于超新星遗迹，如SN 1006。这种解释解决了我们早先对这种发射的纯热解释中的一个问题，即穿过激波的密度压缩需要比理论上预期的因子4大得多。我们描述了一个自洽模型的波瓣动力学和冲击特性，使用外壳的热发射波瓣的北部，以估计波瓣压力。基于这个模型，我们估计瓣正在以2600 km s-1的速度向西南方向扩张，相对于周围介质大约为8马赫。我们讨论了整个冲击区的光谱指数的空间变化，得出的结论是，我们的观察约束γmax的加速粒子在冲击的最强的部分是-10 8，从扩散冲击加速理论的预期一致。最后，我们认为这些结果的影响，生产超高能宇宙射线（UHECRs）和TeV发射从半人马座A，得出的结论是，冲击波前区域是不太可能是一个重要的来源的UHECRs，但TeV发射从这个地区预计在水平相当于目前的限制在TeV能量，合理假设的磁场强度。
We present new results on the shock around the southwest radio lobe of Centaurus A using data from the Chandra Very Large Programme observations (740 ks total observing time). The X-ray spectrum of the emission around the outer southwestern edge of the lobe is well described by a single power-law model with Galactic absorption ‐ thermal models are strongly disfavoured, except in the region closest to the nucleus. We conclude that a significant fraction of the X-ray emission around the southwest part of the lobe is synchrotron, not thermal. We infer that in the region where the shock is strongest and the ambient gas density lowest, the inflation of the lobe is accelerating particles to X-ray sync hrotron emitting energies, similar to supernova remnants such as SN1006. This interpretation resolves a problem of our earlier, purely thermal, interpretation for this emission, namely t hat the density compression across the shock was required to be much larger than the theoretically expected factor of 4. We describe a self-consistent model for the lobe dynamics and shock properties using the shell of thermal emission to the north of the lobe to estimate the lobe pressure. Based on this model, we estimate that the lobe is expanding to the southwest with a velocity of �2600 km s 1 , roughly Mach 8 relative to the ambient medium. We discuss the spatial variation of spectral index across the shock region, concluding that our observations constrain γmax for the accelerated particles to be �10 8 at the strongest part of the shock, consistent with expectat ions from diffusive shock acceleration theory. Finally, we consider the implications of these results for the production of ultra-high energy cosmic rays (UHECRs) and TeV emission from Centaurus A, concluding that the shock front region is unlikely to be a significant source of UHECRs, but that TeV emission from this region is expected at levels comparable to current limits at TeV energies, for plausible assumed magnetic field strength s.
DOI：
10.1111/j.1365-2966.2008.13162.x
发表时间：
2008-02
影响因子：
4.8
作者：
J. Croston;M. Hardcastle;M. Birkinshaw;D. Worrall;R. Laing
通讯作者：
J. Croston;M. Hardcastle;M. Birkinshaw;D. Worrall;R. Laing