Submilliarcsecond Polarimetric Imaging of Blazar Jets at 43 GHz
Submilliarcsecond Polarimetric Imaging of Blazar Jets at 43 GHz
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DOI：
10.1086/306112
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发表时间：
1998-09
期刊：
影响因子：
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通讯作者：
M. Lister;A. Marscher;W. Gear
中科院分区：
文献类型：
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作者：
M. Lister;A. Marscher;W. Gear
我们展示了用甚长基线阵列（Very Long Baseline Array）获得的43 GHz偏振图像，其中包括四个blazars(0829+046、1055+018、1334-127和天秤座AP)，以及四个活动星系核，它们作为偏振校准器（DA 193、OJ 287、3C 279和1611+343）。其中6个天体是Nartallo等人的毫米波偏振耀变体监测样本的成员。我们发现，在我们的样本中，带座BL天体和类星体的毫米波偏振特性总体上没有差异。这与之前在厘米波长的发现形成了对比，在厘米波长的发现中，推断出类星体的磁场主要与喷流对齐，而在BL Lac物体中发现了垂直的结构。除了低光偏振类星体1611+343外，我们样本中所有未解析的耀变体核都推断出了垂直于内部喷流方向的磁场方向。过去的非成像毫米波偏振监测数据表明，这些核心取向在我们的三个样品中是稳定的；这可能是由于强大的，未解决的站立冲击位于非常接近的喷气机的基础。我们还在耀变体的喷流中发现了中等大小的极化成分，它们的电矢量与局部喷流方向呈斜角。我们发现，观测到的电矢量不对准角的分布不能用相对于射流轴具有任意倾角的单一倾斜冲击来拟合。这样的人口预测了与喷流相关的相对论效应产生的与喷流轴对齐的电偏振矢量的过多冲击。我们发现数据更符合一种情况，即极化射流成分仅仅是增强区域，其磁场方向由除冲击以外的某些机制控制。
We present 43 GHz polarization images obtained with the Very Long Baseline Array of four blazars (0829+046, 1055+018, 1334-127, and AP Librae), as well as four active galactic nuclei, which served as polarization calibrators (DA 193, OJ 287, 3C 279, and 1611+343). Six of these objects are members of the Nartallo et al. millimeter-wave polarization blazar monitoring sample. We find no differences in the overall millimeter-wave polarization properties of the BL Lacertae objects and quasars in our sample. This is in contrast to previous findings at centimeter wavelengths, in which the inferred magnetic fields of quasars are found to be predominantly aligned with the jet, while perpendicular configurations are found in BL Lac objects. With the exception of 1611+343, a low optical polarization quasar, all of the unresolved blazar cores in our sample have inferred magnetic field orientations perpendicular to the inner jet direction. Past nonimaging millimeter-wave polarization monitoring data have shown that these core orientations are stable in three of our sample objects; this may be due to strong, unresolved standing shocks located very close to the base of the jet. We also detect in the jets of blazars a moderate-sized population of polarized components having electric vectors that lie at an oblique angle to the local jet direction. We find that the observed distribution of electric vector misalignment angles cannot be fitted by a single population of oblique shocks having arbitrary inclinations with respect to the jet axis. Such a population predicts an overabundance of shocks with electric polarization vectors aligned with the jet axis, produced by relativistic effects associated with the jet flow. We find the data to be more consistent with a scenario in which the polarized jet components are merely enhanced regions whose magnetic field orientations are controlled by some mechanism other than shocks.