The nuclear radio-optical properties of intermediate-redshift FR II radio galaxies and quasars
The nuclear radio-optical properties of intermediate-redshift FR II radio galaxies and quasars
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中红移 FR II 射电星系和类星体的核射电光学特性
DOI：
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发表时间：
2004
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影响因子：
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通讯作者：
A. Capetti
中科院分区：
文献类型：
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作者：
S. Varano;M. Chiaberge;F. Macchetto;A. Capetti
我们将HST观测到的3CR天体核的研究扩展到更高红移的FR II射电源（0.4 < z < 0.6）。我们的结果反映了低红移FR II的发现。原子核在光学和射电亮度形成的平面上的位置与其光谱分类有关：高激发星系和低激发星系的原子核都位于FR I源的相关性上，而宽线天体则有明显的光学过剩。当我们考虑（OIII）发射线相对于其光学光度的等效宽度时，这些源的核性质就能得到更好的理解。即使在这里考虑的红移范围内，低激发星系也表现出特殊的核性质，更类似于在FR i中观察到的那些。这证实了并非所有窄线FR II都与类星体统一。我们的发现对FR ii -类星统一方案具有重要意义：通过重新考虑所有z < 1的3CR射电星系的核性质分类，我们得出了不同红移箱的模糊环面开口角度。我们发现，当z < 0时，遮光结构的覆盖因子随着红移的增加而减小（θ ~ 44◦）。3t oθ ~ 56◦为0.5 < z < 1)。我们认为这种行为可以用后退环面模型的框架来解释，在后退环面模型中，环面开口的角度随着中心黑洞周围吸积盘亮度的增加而增加。
We extend the study of the nuclei of 3CR objects as seen with the HST to higher-redshift FR II radio sources (0.4 < z < 0.6). Our results reflect what has been found for FR II of lower redshift. The position of the nuclei in the plane formed by optical and radio luminosities is related to their optical spectral classification: the nuclei of both high and low excitation galaxies lie on the correlation found for FR I sources, while broad-line objects have a significant optical excess. The nuclear properties of these sources are better understood when we consider the equivalent widths of the (OIII) emission line with respect to their optical luminosities. Even in the range of redshift considered here, low excitation galaxies show peculiar nuclear properties, more similar to those observed in FR I. This confirms that not all narrow-line FR II are unified with quasars. Our findings have important implications for the FR II-quasar unification scheme: by reconsidering the classification of all 3CR radio galaxies with z < 1 in the light of their nuclear properties, we derive the opening angle of the obscuring torus for different redshift bins. We find that the covering factor of the obscuring structure decreases as the redshift increases (θ ∼ 44 ◦ for z < 0. 3t oθ ∼ 56 ◦ for 0.5 < z < 1). We argue that this behavior may be interpreted in the framework of the receding torus model, in which the opening angle of the torus increases as the luminosity of the accretion disk around the central black hole increases.