TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet-猫眼课题宝

DOI：

10.1051/0004-6361/201423948

发表时间：

2014-07

期刊：

Astronomy and Astrophysics

影响因子：

6.5

通讯作者：

中科院分区：

物理与天体物理2区

文献类型：

作者：

C. Müller;M. Kadler;R. Ojha;R. Ojha;R. Ojha;M. Perucho;C. Grossberger;E. Ros;E. Ros;J. Wilms;J. Blanchard;M. Böck;B. Carpenter;M. Dutka;P. G. Edwards;H. Hase;S. Horiuchi;A. Kreikenbohm;J. Lovell;A. Markowitz;A. Markowitz;C. Phillips;C. Plötz;T. Pursimo;J. Quick;R. Rothschild;R. Schulz;T. Steinbring;J. Stevens;J. Trüstedt;A. Tzioumis

上下文半人马座A（Cen A）是距离地球最近的射电活跃星系核。甚长基线干涉测量（VLBI）使我们能够在毫角秒尺度上研究射电喷流-反喷流系统的光谱和运动学行为，为喷流发射和传播模型提供必要的信息。目标。在TANAMI监测的框架下，我们在亚秒差距尺度上研究了Cen A的运动学和复杂结构。我们已经研究了3.5年多的Cen A中心秒差距喷流结构的演变。个别射流组件的自行分析，使我们能够约束射流的形成和传播，并测试建议的相关性增加的高能量通量与射流喷射事件。Cen A是进行这种详细研究的特殊实验室，因为它的接近度转化为无与伦比的线性分辨率，其中1毫弧秒对应于0.018 pc。方法.作为南半球VLBI监测计划TANAMI的一个目标，澳大利亚长基线阵列（LBA）和南极洲，智利，新西兰和南非的相关望远镜在8.4 GHz下大约每六个月进行一次Cen A的观测，并辅以准同步22.3 GHz观测。结果本文介绍了前七个时期在8.4 GHz的Cen A上进行的高分辨率TANAMI VLBI观测，在（亚）毫角秒尺度上分辨喷流。它们显示了亚秒差距尺度喷流的扩散运动，在更远的下游，喷流变得光学薄，其分量速度明显更高。我们确定了0：1c至0：3c范围内的表观组件速度，并确定了长期稳定的功能。结合喷流与反喷流的比例，我们可以将视线的角度限制在12 45。结论.高分辨率的运动学是最好的解释由脊柱鞘结构支持的下游加速发生的射流变得光学薄。在底层的连续气流之上，TANAMI的观测清楚地分辨出了个别的喷流特征。流动似乎被障碍物中断，导致表面亮度和环流射流行为局部下降。我们提出了一个喷星相互作用的情况来解释这种外观。射流喷射时间与高X射线通量阶段的比较产生了X射线发射和射流活动增加的开始的部分重叠，但是有限的数据不支持稳健的相关性。

Context. Centaurus A (Cen A) is the closest radio-loud active galactic nucleus. Very Long Baseline Interferometry (VLBI) enables us to study the spectral and kinematic behavior of the radio jet-counterjet system on milliarcsecond scales, providing essential information for jet emission and propagation models. Aims. In the framework of the TANAMI monitoring, we investigate the kinematics and complex structure of Cen A on subparsec scales. We have been studying the evolution of the central parsec jet structure of Cen A for over 3.5 years. The proper motion analysis of individual jet components allows us to constrain jet formation and propagation and to test the proposed correlation of increased high-energy flux with jet ejection events. Cen A is an exceptional laboratory for such a detailed study because its proximity translates to unrivaled linear resolution, where one milliarcsecond corresponds to 0.018 pc. Methods. As a target of the southern-hemisphere VLBI monitoring program TANAMI, observations of Cen A are done approximately every six months at 8.4 GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, New Zealand, and South Africa, complemented by quasi-simultaneous 22.3 GHz observations. Results. The first seven epochs of high-resolution TANAMI VLBI observations at 8.4 GHz of Cen A are presented, resolving the jet on (sub-)milliarcsecond scales. They show a di erential motion of the subparsec scale jet with significantly higher component speeds farther downstream where the jet becomes optically thin. We determined apparent component speeds within a range of 0:1c to 0:3c and identified long-term stable features. In combination with the jet-to-counterjet ratio, we can constrain the angle to the line of sight to 12 45 . Conclusions. The high-resolution kinematics are best explained by a spine-sheath structure supported by the downstream acceleration occurring where the jet becomes optically thin. On top of the underlying, continuous flow, TANAMI observations clearly resolve individual jet features. The flow appears to be interrupted by an obstacle causing a local decrease in surface brightness and circumfluent jet behavior. We propose a jet-star interaction scenario to explain this appearance. The comparison of jet ejection times to high X-ray flux phases yields a partial overlap of the onset of the X-ray emission and increasing jet activity, but the limited data do not support a robust correlation.

TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet

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