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arXiv 1001.3140astro-ph.CO
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Swift观测到的软X射线选AGN的同时光学-X射线谱能量分布

The Simultaneous Optical-to-X-ray Spectral Energy Distribution of Soft X-ray Selected AGN observed by Swift

Dirk Grupe, S. Komossa, Karen M. Leighly, Kim L. Page

摘要:

本文报道了雨燕对92个明亮软X射线选定活动星系核(AGN)的观测结果。这个样本代表了最大数量的活动星系核观测研究光谱能量分布(SED)的活动星系核的同时光学/紫外和X射线数据。这项研究的主要动机是了解活动星系核的SED在光学/UV X射线制度,并提供热辐射校正,这是很重要的,在确定爱丁顿比L/Ledd。特别是,我们严格探索的依赖性的UV-EUV贡献的辐射热校正的假设EUV光谱形状。我们发现强相关性的光谱斜率α-x和α-UV与L/Ledd。虽然窄线塞弗特1星系(NLS 1 s)比宽线塞弗特1星系(BLS 1 s)具有更陡的α-x和更高的L/Ledd,但它们的光学/UV到X射线光谱斜率α-ox和光学/UV斜率α-UV非常相似。NLS 1 s的平均SED表明,一般来说,这类活动星系核在紫外和硬X射线能量下似乎比BLS 1更暗。我们发现活动星系核的α-x和α-UV之间有很强的相关性,X射线光谱斜率α-x <1.6。对于X射线谱较陡的活动星系核,这一关系以及α-x与L/Ledd的关系都不成立。在α-x $\approx$ 1.6时,L/Ledd达到1。我们注意到NLS 1和BLS 1之间的α-UV- L/Ledd关系存在偏移。我们认为,α-UV是一个很好的估计L/Ledd,并建议α-UV可以用来估计L/Ledd在高红移类星体。尽管NLS 1在X射线中表现出高度可变性,但它们在UV中的变化很小。

英文摘要:

We report Swift observations of a sample of 92 bright soft X-ray selected active galactic nuclei (AGN). This sample represents the largest number of AGN observed to study the spectral energy distribution (SED) of AGN with simultaneous optical/UV and X-ray data. The principal motivation of this study is to understand the SEDs of AGN in the optical/UV to X-ray regime and to provide bolometric corrections which are important in determining the Eddington ratio L/Ledd. In particular, we rigorously explore the dependence of the UV-EUV contribution to the bolometric correction on the assumed EUV spectral shape. We find strong correlations of the spectral slopes alpha-x and alpha-UV with L/Ledd. Although Narrow-Line Seyfert 1 galaxies (NLS1s) have steeper alpha-x and higher L/Ledd than Broad-Line Seyfert 1 galaxies (BLS1s), their optical/UV to X-ray spectral slopes alpha-ox and optical/UV slopes alpha-UV are very similar. The mean SED of NLS1s shows that in general this type of AGN appears to be fainter in the UV and at hard X-ray energies than BLS1s. We find a strong correlation between alpha-x and alpha-UV for AGN with X-ray spectral slopes alpha-x<1.6. For AGN with steeper X-ray spectra, both this relation and the relation between alpha-x and L/Ledd break down. At alpha-x$\approx$1.6, L/Ledd reaches unity. We note an offset in the alpha-UV - L/Ledd relation between NLS1s and BLS1s. We argue that alpha-UV is a good estimator of L/Ledd and suggest that alpha-UV can be used to estimate L/Ledd in high-redshift QSOs. Although NLS1s appear to be highly variable in X-rays they only vary marginally in the UV.

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