VSOP polarization observations of the BL Lacertae object OJ 287
VSOP polarization observations of the BL Lacertae object OJ 287
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DOI：
10.1046/j.1365-8711.2001.04147.x
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发表时间：
2001-02
影响因子：
4.8
通讯作者：
D. Gabuzda;J. Gómez
中科院分区：
文献类型：
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作者：
D. Gabuzda;J. Gómez
BL Lacertae 物体 OJ 287 的 VLBI 总强度和线性偏振图像已使用全球地面阵列和 HALCA 轨道天线获得，并在两周前使用 VLBA 获得。在地基 6 厘米图像中，源主要是核心喷流双结构，其组成部分基本上尚未解析。轨道天线的基线解析了这两个紧凑的组件。在 VSOP 图像中，地基“核心”分裂成几个不同的组成部分，表明该区域主要由喷射发射的明亮、光学薄结的贡献所主导。在 1.3 厘米图像中观察到非常相似的结构。核心中的磁场是横向的，在内射流中变成纵向的，然后急剧过渡到远离核心的横向磁场区域。这表明，由于激波的作用，外部射流中的场在横向上变得高度有序。靠近核心的纵向场扩展区域的物理性质尚不清楚。由于从光学厚（6 cm）到光学薄（1.3 cm）状态的转变，在宽间隔频率下几乎同时进行具有相当分辨率的观测使得能够检测到核心偏振位置角≃90°的旋转。
VLBI total intensity and linear polarization images of the BL Lacertae object OJ 287 have been obtained at using a global ground array and the HALCA orbiting antenna, and at two weeks earlier using the VLBA. In the ground-based 6-cm images, the source is dominated by a core–jet double structure the components of which are essentially unresolved. The baselines to the orbiting antenna resolve both of these compact components. In the VSOP images, the ground-based ‘core’ breaks up into several distinct components, demonstrating that this region is dominated by the contribution of bright, optically thin knots of jet emission. A very similar structure is observed in the 1.3-cm image. The magnetic field in the core is transverse, becomes longitudinal in the inner jet, then makes a sharp transition to a region of transverse field further from the core. This suggests that the field in the outer jet has become highly ordered in the transverse direction owing to the action of a shock; the physical nature of the extended region of longitudinal field closer to the core is not clear. The availability of nearly simultaneous observations with comparable resolution at widely spaced frequencies enabled detection of a ≃90° rotation in polarization position angle for the core, owing to the transition from the optically thick (6 cm) to the optically thin (1.3 cm) regime.