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arXiv 1304.7690astro-ph.HE
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CDFS中的XMM深度巡天V.来自遥远宇宙活动星系核的铁K线

The XMM Deep survey in the CDFS V. Iron K lines from active galactic nuclei in the distant Universe

S. Falocco, F. J. Carrera, A. Corral, X. Barcons, A. Comastri, R. Gilli, P. Ranalli, C. Vignali, K. Iwasawa, N. Cappelluti, E. Rovilos, I. Georgantopoulos, M. Brusa, F. Vito

摘要:

活动星系核的X射线光谱学提供了直接探测吸积盘内部区域的机会。本文介绍了钱德拉深场南方观测(XMM CDFS)中活动星系核平均XMM-牛顿X射线谱的分析结果。在2-12 keV静止帧波段,用至少一台EPIC相机计算了54个光谱红移和信噪比S/N > 15的活动星系核的平均光谱。我们已经考虑了不同红移的光源和两台EPIC相机的光谱组合效果,以及它们的光谱分辨率;我们使用彻底的模拟检查了我们的结果。我们探讨了遥远的活动星系核的Fe线成分,重点是来自远离中心发动机的区域的窄核和假定的相对论成分(来自吸积盘)。平均光谱显示出非常显著的Fe特征。我们对等效宽度(EW)的独立于模型的估计表明在更宽的范围内EW更高。该线被建模为未分辨的高斯,在6.8 σ处是显著的,并且具有EW=95 eV(全样本)。将相对论分布添加到窄分量(在完整样品中,相对论谱线和窄谱线的EW分别为140 eV和67 eV),可以同样很好地拟合电流数据。由于高品质的XMM CDFS光谱和详细的建模的连续和仪器的影响,我们已经表明,最遥远的活动星系核表现出非常显着的铁排放功能。它可以用窄线和宽线来建模。我们发现了非常接近和远离中央引擎的材料反射的诱人证据。这两个特征的EW与在单个附近活动星系核中观测到的相似,因此它们一定是活动星系核的普遍特征,否则平均值将小于观测值。

英文摘要:

X-ray spectroscopy of active galactic nuclei (AGN) offers the opportunity to directly probe the inner regions of the accretion disk. We present the results of our analysis of average AGN XMM-Newton X-ray spectra in the Chandra Deep Field South observation (XMM CDFS). We computed the average spectrum of a sample of 54 AGN with spectroscopic redshifts and signal-to-noise ratio S/N > 15 in the 2-12 keV rest-frame band in at least one EPIC camera. We have taken the effects of combining spectra from sources at different redshifts and both EPIC cameras into account, as well as their spectral resolution; we checked our results using thorough simulations. We explored the Fe line components of distant AGN focusing on the narrow core which arises from regions far from the central engine and on the putative relativistic component (from the accretion disk). The average spectrum shows a highly significant Fe feature. Our model-independent estimates of the equivalent width (EW) suggest a higher EW in a broader range. The line, modelled as an unresolved Gaussian, is significant at 6.8 sigma and has an EW=95 eV (full sample). The current data can be fitted equally well adding a relativistic profile to the narrow component (in the full sample, EW=140 eV and 67 eV respectively for the relativistic and narrow lines). Thanks to the high quality of the XMM CDFS spectra and to the detailed modelling of the continuum and instrumental effects, we have shown that the most distant AGN exhibit a highly significant Fe emission feature. It can be modelled both with narrow and broad lines. We found tantalising evidence for reflection by material both very close and far away from the central engine. The EW of both features are similar to those observed in individual nearby AGN, hence they must be a widespread characteristic of AGN, since otherwise the average values would be smaller than observed.

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