Parsec-Scale Circular Polarization Observations of 40 Blazars
Parsec-Scale Circular Polarization Observations of 40 Blazars
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40 个耀变体的秒差距尺度圆偏振观测
DOI：
10.1086/321568
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. Wardle
中科院分区：
文献类型：
--
作者：
D. Homan;J. Attridge;J. Wardle
我们提出了圆偏振的结果，从5 GHz的调查秒差距尺度的偏振特性的40个活动星系核（AGN）的VLBA。我们发现11个圆偏振检测在3 σ或更高的水平。这几乎是VLBI分辨率下圆极化检测到的源数量的四倍。我们发现在我们的样本分数线和圆偏振之间没有相关性。一个可能的解释是外部法拉第去极化在核心的活动星系核，减少线偏振，但离开圆偏振不变。将我们和其他最近的结果与20年前的观测结果进行比较，我们发现，在六种情况中的五种情况下，今天的源与20年前具有相同的圆偏振符号。这表明喷流的长期性质的存在，例如净磁通量的极性，它在时间尺度上比单独爆发的时间尺度长得多。
We present circular polarization results from a 5 GHz survey of the parsec-scale polarization properties of 40 active galactic nuclei (AGNs) made with the VLBA. We find 11 circular polarization detections at the 3 σ level or higher. This nearly quadruples the number of sources detected in circular polarization at VLBI resolution. We find no correlation between fractional linear and circular polarization across our sample. A likely explanation is external Faraday depolarization in the cores of AGNs which reduces linear polarization but leaves circular polarization unchanged. In comparing ours and other recent results to observations made ~20 years ago, we find that, in five of six cases, sources have the same sign of circular polarization today as they did 20 years ago. This suggests the presence of a long-term property of the jets, such as the polarity of a net magnetic flux, which is stable on timescales much longer than those of individual outbursts.