高红移3CRR源的中红外光谱
Mid-infrared spectroscopy of high-redshift 3CRR sources
摘要：
利用Spitzer空间望远镜获得了3CRR星表中11个类星体和9个射电星系的9- 16 μ静止坐标系的红移为1.0<z<1.4的光谱。这个完整的通量有限的178兆赫选择的样品是无偏的方向，因此适合于研究在最强大的活动星系核（AGN）的方向依赖的影响。射电星系的平均光谱显示出明显的硅酸盐吸收特征（τ_9.7 μ = 1.1），而类星体的平均光谱则显示出硅酸盐的发射。平均射电星系光谱匹配尘埃吸收的平均类星体光谱的形状和整体通量水平。个别物体的数据符合这些结果。硅酸盐深度的趋势，以增加减少核心部分的射电源进一步支持，对于这个样本，方向是主要的驱动程序之间的差异，射电星系和类星体，所预测的活动星系核统一。然而，比较我们的高Z样本与较低的红移3CRR对象显示，高Z射电星系MIR连续体的吸收低于预期的低光度源的放大版本，我们讨论了一些可能解释这些趋势的影响。
英文摘要：
Using the Spitzer Space Telescope, we have obtained rest frame 9-16mu spectra of 11 quasars and 9 radio galaxies from the 3CRR catalog at redshifts 1.0<z<1.4. This complete flux-limited 178MHz-selected sample is unbiased with respect to orientation and therefore suited to study orientation-dependent effects in the most powerful active galactic nuclei (AGN). The mean radio galaxy spectrum shows a clear silicate absorption feature (tau_9.7mu = 1.1) whereas the mean quasar spectrum shows silicates in emission. The mean radio galaxy spectrum matches a dust-absorbed mean quasar spectrum in both shape and overall flux level. The data for individual objects conform to these results. The trend of the silicate depth to increase with decreasing core fraction of the radio source further supports that for this sample, orientation is the main driver for the difference between radio galaxies and quasars, as predicted by AGN unification. However, comparing our high-z sample with lower redshift 3CRR objects reveals that the absorption of the high-z radio galaxy MIR continuum is lower than expected from a scaled up version of lower luminosity sources, and we discuss some effects that may explain these trends.
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