Average Fe K$\mathsf{\alpha}$ emission from distant AGN
Average Fe K$\mathsf{\alpha}$ emission from distant AGN
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DOI：
10.1051/0004-6361:200810168
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发表时间：
2008-10
影响因子：
6.5
通讯作者：
A. Corral;M. Page;F. J. Carrera;X. Barcons;S. Mateos;J. Ebrero;M. Krumpe;A. Schwope;J. Tedds;M. G. Watson
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文献类型：
--
作者：
A. Corral;M. Page;F. J. Carrera;X. Barcons;S. Mateos;J. Ebrero;M. Krumpe;A. Schwope;J. Tedds;M. G. Watson
上下文X射线背景综合模型中最重要的参数之一是超大质量黑洞的平均吸积效率。这可以从活动星系核（AGN）的X射线谱中看到的宽相对论Fe线的形状推断出来。几项研究试图测量活动星系核不同深度的平均铁发射特性，但结果大相径庭。目标。我们计算的平均Fe发射从一个大的和有代表性的样本的活动星系核的X射线光谱红移~3.5。方法.我们开发了一种计算静止框架X射线平均谱的方法，并将其应用于一个大样本（600多个对象）的类型1活动星系核从两个互补的介质灵敏度调查的基础上XMM-牛顿数据，AXIS和XWAS样本。该方法利用中低质量光谱，无需将复杂模型拟合到各个光谱，而是计算整个样本的平均光谱。通过比较真实的模拟数据进行了广泛的质量测试，并推导出了在基础连续体上检测任何特征的意义。结果我们检测到一个未解决的Fe K α发射线约6.4 keV的EW ~ 90 eV的99.9%的显着性，但我们没有发现任何令人信服的证据，任何显着的广泛的相对论发射线在最终的平均光谱。窄线周围的幂律偏差最好由冷或低电离物质产生的反射分量表示。在3 σ置信水平下，我们估计了任何400 eV相对论谱线的EW上限。我们还轻微地检测到所谓的岩泽谷口效应的EW的未解决的发射线，这似乎较弱的更高的光度AGN。结论.我们计算了平均相对论Fe K α线贡献的上限，该上限明显低于以前报道的类似分析的值。然而，我们的结果与当地活动星系核样品的个别分析非常一致。我们将这种差异归因于我们更复杂的方法来模拟潜在的连续体，源种群的内在差异，和/或各种样品的单个光谱的不均匀的数据质量。
Context. One of the most important parameters in the XRB ( X-ray background ) synthesis models is the average efficiency of accretion onto SMBH ( super-massive black holes ). This can be inferred from the shape of broad relativistic Fe lines seen in X-ray spectra of AGN ( active galactic nuclei ). Several studies have tried to measure the mean Fe emission properties of AGN at different depths with very different results. Aims. We compute the mean Fe emission from a large and representative sample of AGN X-ray spectra up to redshift ~3.5. Methods. We developed a method of computing the rest-frame X-ray average spectrum and applied it to a large sample (more than 600 objects) of type 1 AGN from two complementary medium sensitivity surveys based on XMM-Newton data, the AXIS and XWAS samples. This method makes use of medium-to-low quality spectra without needing to fit complex models to the individual spectra but with computing a mean spectrum for the whole sample. Extensive quality tests were performed by comparing real to simulated data, and a significance for the detection of any feature over an underlying continuum was derived. Results. We detect with a 99.9% significance an unresolved Fe K α emission line around 6.4 keV with an EW ~ 90 eV, but we find no compelling evidence of any significant broad relativistic emission line in the final average spectrum. Deviations from a power law around the narrow line are best represented by a reflection component arising from cold or low-ionization material. We estimate an upper limit for the EW of any relativistic line of 400 eV at a 3 σ confidence level. We also marginally detect the so-called Iwasawa-Taniguchi effect on the EW for the unresolved emission line, which appears weaker for higher luminosity AGN. Conclusions. We computed an upper limit for the average relativistic Fe K α line contribution that is significantly lower than previously reported values from similar analyses. Our results, however, are in excellent agreement with individual analyses of local AGN samples. We attribute this difference either to our more sophisticated method of modeling the underlying continuum, to intrinsic differences in source populations, and/or to the uneven data quality of the individual spectra of the various samples.