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arXiv 1202.0868astro-ph.HE
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与Fermi-LAT源2FGLJ 1629.4 +8236相关的巨型射电星系NGC6251中扩展叶的朱雀X射线成像

Suzaku X-ray Imaging of the Extended Lobe in the Giant Radio Galaxy NGC6251 Associated with the Fermi-LAT Source 2FGLJ1629.4+8236

Y. Takeuchi, J. Kataoka, L. Stawarz, Y. Takahashi, K. Maeda, T. Nakamori, C. C. Cheung, A. Celotti, Y. Tanaka, T. Takahashi

摘要:

我们报告了NGC 6251的朱雀X射线成像研究结果,NGC 6251是一个邻近的巨型射电星系,具有中等FR I/II射电性质。我们的指向集中在最近用费米-LAT发现的伽马射线发射峰上,该峰位于西北射电瓣的位置,距离核15弧分。在减去两个“离源”点附近的无线电波瓣,并删除可能的污染物在XIS的视野,我们发现显着的残留X射线发射最有可能扩散的性质。过量X射线发射的光谱很好地符合幂律,其中光子指数Γ= 1.90 +-0.15,0.5 - 8 keV通量为4 x 10^{-13} erg cm^{-2} s^{-1}。我们解释这个弥漫的X射线发射分量是由于逆康普顿上散射的宇宙微波背景光子的超相对论电子内的叶,只有一个小的贡献,从大规模的喷流的光束发射。利用存档的无线电数据的源,我们证明了通过宽带光谱建模的费米-LAT源2FGL J1629.4+8236的射线通量可以很好地占高能量尾的逆康普顿连续波瓣。因此,这个声称的来自NGC 6251西北叶的伽马射线的关联,以及最近对半人马座A扩展叶的费米-LAT成像,表明粒子可能被有效地(重新)加速到超相对论能量,通常在附近的射电星系的扩展射电叶内。

英文摘要:

We report the results of a Suzaku X-ray imaging study of NGC6251, a nearby giant radio galaxy with intermediate FR I/II radio properties. Our pointing direction was centered on the gamma -ray emission peak recently discovered with Fermi-LAT around the position of the north-west radio lobe 15 arcmin offset from the nucleus. After subtracting two "off-source" pointings adjacent to the radio lobe, and removing possible contaminants in the XIS field of view, we found significant residual X-ray emission most likely diffuse in nature. The spectrum of the excess X-ray emission is well fit by a power law with photon index Γ= 1.90 +- 0.15 and a 0.5 - 8 keV flux of 4 x 10^{-13} erg cm^{-2} s^{-1}. We interpret this diffuse X-ray emission component as being due to inverse-Compton up-scattering of the cosmic microwave background photons by ultrarelativistic electrons within the lobe, with only a minor contribution from the beamed emission of the large-scale jet. Utilizing archival radio data for the source, we demonstrate by means of broad-band spectral modeling that the -ray flux of the Fermi-LAT source 2FGL J1629.4+8236 may well be accounted for by the high-energy tail of the inverse-Compton continuum of the lobe. Thus, this claimed association of gamma-rays from the north-west lobe of NGC6251, together with the recent Fermi-LAT imaging of the extended lobes of Centaurus A, indicates that particles may be efficiently (re-)accelerated up to ultrarelativistic energies within extended radio lobes of nearby radio galaxies in general.

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