活动星系核的首次IRAM/PdBI偏振毫米波巡天。I.样本的全局属性
The First IRAM/PdBI Polarimetric Millimeter Survey of Active Galactic Nuclei. I. Global Properties of the Sample
摘要：
我们用IRAM的Plateau de Bure干涉仪（PdBI），在80-267 GHz（波长3.7- 1.1 mm）的观测频率范围内（对应静止坐标系频率82-738 GHz），对86个活动星系核（AGN）的线偏振进行了研究。大量的测量，441，使我们的分析最大的极化活动星系核调查在这个频率范围内的日期。我们通过地球自转偏振测量法提取偏振参数，其偏振分数的中值精度为~0.1%，偏振角的中值精度为~1.2度。对于86个源中的73个，我们至少检测到一次偏振。偏振度高达~ 19%，所有光源的中值为~ 4%。源通量和偏振通常是高度可变的，分数可变性高达~ 60%。我们发现BLLac源平均具有最高的偏振水平。偏振度和红移之间似乎没有相关性，表明自z~2.4以来偏振特性没有实质性变化。我们的偏振和光谱指数分布与在cm/射电波长处观察到的各种样品的结果非常一致;因此，我们的频率范围可能跟踪同步辐射的签名，而没有来自其他发射机制的明显贡献。位于频率>1 THz的“毫米波突变”在我们的调查所覆盖的频率范围内似乎是不可检测的。
英文摘要：
We have studied the linear polarization of 86 active galactic nuclei (AGN) in the observed frequency range 80-267 GHz (3.7-1.1mm in wavelength), corresponding to rest-frame frequencies 82-738 GHz, with the IRAM Plateau de Bure Interferometer (PdBI). The large number of measurements, 441, makes our analysis the largest polarimetric AGN survey in this frequency range to date. We extracted polarization parameters via earth rotation polarimetry with unprecedented median precisions of ~0.1% in polarization fractions and ~1.2 degrees in polarization angles. For 73 of 86 sources we detect polarization at least once. The degrees of polarization are as high as ~19%, with the median over all sources being ~4%. Source fluxes and polarizations are typically highly variable, with fractional variabilities up to ~60%. We find that BLLac sources have on average the highest level of polarization. There appears to be no correlation between degree of polarization and redshift, indicating that there has been no substantial change of polarization properties since z~2.4. Our polarization and spectral index distributions are in good agreement with results found from various samples observed at cm/radio wavelengths; thus our frequency range is likely tracing the signature of synchrotron radiation without noticeable contributions from other emission mechanisms. The "millimeter-break" located at frequencies >1 THz appears to be not detectable in the frequency range covered by our survey.
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