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arXiv 2009.01294astro-ph.HE
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河外喷流3C 111中明亮耀斑和喷射事件的亚毫弧秒成像

Sub-milliarcsecond imaging of a bright flare and ejection event in the extragalactic jet 3C 111

R. Schulz, M. Kadler, E. Ros, M. Perucho, T. P. Krichbaum, I. Agudo, T. Beuchert, M. Lindqvist, K. Mannheim, J. Wilms, J. A. Zensus

备注：
11 pages, 7 figures, accepted for publication by Astronomy & Astrophysics
发表信息：
A&A 644, A85 (2020)
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摘要：

射电大活动星系核中的耀斑被认为与向致密喷流底部注入新鲜等离子体有关。这样的耀斑通常是最强的，并且在较短的无线电波长上出现得更早。因此，在毫米波长的VLBI最适合于研究与发射耀斑相关的致密喷流的最早的结构变化。我们研究了在2007年耀斑发展成一个主要的射电爆发后，附近（z=0.049）伽马射线明亮的射电星系3C 111的秒差距尺度喷流的形态变化。分析了2007 - 2008年全球毫米VLBI阵列（GMVA）在86 GHz对3C 111的三次连续观测，获得了~ 45 μ as的高角分辨率。此外，我们利用单碟射电通量密度测量的F-伽马和POLAMI方案，档案单碟和VLBI数据。我们将耀斑分解为多个等离子体成分，这些成分具有独特的形态，类似于一个弯曲的直射流。与耀斑相关的特征以~4.0c至~4.5c的视速度移动，并且可以在较晚的时期以较低的频率追踪。在喷流底部附近，我们发现了两个明亮的特征，其亮度温度高达~ 10^11 K，我们将其与喷流中的核心和静止特征联系起来。耀斑导致了多个新的喷流组件，表明在喷射过程中的动态调制。我们解释的弯曲状的功能作为一个直接的结果的爆发，这使得它可以跟踪射流的横向结构。在这种情况下，组件遵循不同的路径，在急流与预期的脊椎鞘结构，这是没有看到在中间水平的活动一致。在3C 111未来明亮的射电耀斑期间协调多波长观测的可能性使该源成为探测射电伽马射线连接的绝佳目标。

英文摘要：

Flares in radio-loud AGN are thought to be associated with the injection of fresh plasma into the compact jet base. Such flares are usually strongest and appear earlier at shorter radio wavelengths. Hence, VLBI at mm-wavelengths is best suited to study the earliest structural changes of compact jets associated with emission flares. We study the morphological changes of the parsec-scale jet in the nearby (z=0.049) gamma-ray bright radio galaxy 3C111 following a flare that developed into a major radio outburst in 2007. We analyse three successive observations of 3C111 at 86 GHz with the Global mm-VLBI Array (GMVA) between 2007 and 2008 which yield a very high angular resolution of ~45muas. In addition, we make use of single-dish radio flux density measurements from the F-GAMMA and POLAMI programmes, archival single-dish and VLBI data. We resolve the flare into multiple plasma components with a distinct morphology resembling a bend in an otherwise remarkably straight jet. The flare-associated features move with apparent velocities of ~4.0c to ~4.5c and can be traced also at lower frequencies in later epochs. Near the base of the jet, we find two bright features with high brightness temperatures up to ~10^11K, which we associate with the core and a stationary feature in the jet. The flare led to multiple new jet components indicative of a dynamic modulation during the ejection. We interpret the bend-like feature as a direct result of the outburst which makes it possible to trace the transverse structure of the jet. In this scenario, the components follow different paths in the jet stream consistent with expectations for a spine-sheath structure, which is not seen during intermediate levels of activity. The possibility of coordinated multiwavelength observations during a future bright radio flare in 3C111 makes this source an excellent target for probing the radio-gamma-ray connection.

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