Spitzer Observations of 3C Quasars and Radio Galaxies: Mid-Infrared Properties of Powerful Radio Sources
Spitzer Observations of 3C Quasars and Radio Galaxies: Mid-Infrared Properties of Powerful Radio Sources
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DOI：
10.1086/511969
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发表时间：
2006-06
期刊：
影响因子：
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通讯作者：
K. Cleary;C. Lawrence;J. Marshall;L. Hao;D. M. J. P. Laboratory;C. I. O. Technology.;C. University-C.-Univers
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文献类型：
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作者：
K. Cleary;C. Lawrence;J. Marshall;L. Hao;D. M. J. P. Laboratory;C. I. O. Technology.;C. University-C.-Univers
我们用斯皮策上的红外光谱和红外光谱仪测量了红移为0.4≤z≤1.2的3CRR星系和类星体的无取向样品的中红外辐射。除了一个以外，所有的源都检测到了强大的发射(L24μm&Gt；1022.4 W HZ-1sr-1)。我们将斯皮策数据和文献中的其他测量结果与同步加速器和尘埃成分进行了匹配。美国国税局的数据对FIT提供了强有力的约束。在15μm时，类星体的亮度通常是具有相同各向同性射电功率的射电星系的4倍。根据我们的拟合，这种差异的一半可以归因于类星体中非热辐射的存在，而不是射电星系。另一半与射电星系的尘埃吸收一致，但与类星体的吸收不一致。拟合的光学深度与核心优势反相关，由此我们推断中央引擎周围尘埃的赤道分布。对于具有核心优势因子R>；10-2的对象，9.7μm处的中位光学厚度为≈0.4；对于具有R≤10-2的对象，其中值光学厚度为≈1.1。因此，我们解决了FR II类星体和星系统一的一个长期存在的问题：类星体在中红外波段比星系更明亮，这是因为类星体中的多普勒增强同步辐射和星系中的消光，这两个效应都与方向有关。
We have measured mid-infrared radiation from an orientation-unbiased sample of 3CRR galaxies and quasars at redshifts 0.4 ≤ z ≤ 1.2 with the IRS and MIPS instruments on Spitzer. Powerful emission (L24 μm > 1022.4 W Hz-1 sr-1) was detected from all but one of the sources. We fit the Spitzer data and other measurements from the literature with synchrotron and dust components. The IRS data provide powerful constraints on the fits. At 15 μm, quasars are typically 4 times brighter than radio galaxies with the same isotropic radio power. Based on our fits, half of this difference can be attributed to the presence of nonthermal emission in the quasars but not the radio galaxies. The other half is consistent with dust absorption in the radio galaxies but not the quasars. Fitted optical depths are anticorrelated with core dominance, from which we infer an equatorial distribution of dust around the central engine. The median optical depth at 9.7 μm for objects with core dominance factor R > 10-2 is ≈0.4; for objects with R ≤ 10-2, it is ≈1.1. We have thus addressed a long-standing question in the unification of FR II quasars and galaxies: quasars are more luminous in the mid-infrared than galaxies because of a combination of Doppler-boosted synchrotron emission in quasars and extinction in galaxies, both orientation-dependent effects.