Probing the jet base of the blazar PKS 1830−211 from the chromatic variability of its lensed images - Serendipitous ALMA observations of a strong gamma-ray flare
Probing the jet base of the blazar PKS 1830−211 from the chromatic variability of its lensed images - Serendipitous ALMA observations of a strong gamma-ray flare
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从其透镜图像的色彩变化探测耀变体 PKS 1830−211 的喷流底部 - 对强烈伽马射线耀斑的偶然 ALMA 观测
DOI：
10.1051/0004-6361/201322131
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发表时间：
2013
影响因子：
6.5
通讯作者：
M. Zwaan
中科院分区：
文献类型：
--
作者：
I. Martí;S. Muller;F. Combes;S. Aalto;A. Beelen;J. Darling;M. Guélin;Christian Henkel;Christian Henkel;C. Horellou;J. Marcaide;S. Martin;K. Menten;Dinh V;M. Zwaan
活动星系核喷流的发射机制在观测上受到的限制很小，因为这些物体距离很远，而且所涉及的尺度很小（亚秒差距）。为了更好地约束理论模型，从靠近射流物理基础的区域获得信息尤为重要，在该区域发生等离子体加速。在本文中，我们报告了z = 2.5的blazar PKS 1830−211的多历元和多频率连续观测，阿尔马，偶然与费米-LAT报告的强γ射线耀斑相吻合。耀变体被一个z = 0.89的前景星系所透镜化，两个明亮的致密核心图像相隔1“”。我们的阿尔马观测分别解析了这两幅图像（尽管不是它们的任何子结构），我们研究了在γ射线耀斑期间，它们的相对通量比随时间（四个历元分布在两幅透镜图像之间的时间延迟的近三倍）和频率（在350和1050 GHz之间，blazar的静止帧）的变化。特别是，我们检测到一个显着的频率依赖行为的通量比，这意味着存在的一个色结构的耀变体（即，核心移位效应）。我们排除了微透镜和毫透镜效应的可能性，并提出了一个简单的模型，而不是等离子体激元喷射在耀变体的喷流来解释的时间和频率的变化的流量比。我们认为PKS 1830−211可能是探测耀变体喷流底部亚毫米波长活动的最佳光源之一，这要归功于该系统的特殊几何结构。在前景z = 0.89星系的吸收研究中核心移动的含义（例如，基本常数的宇宙学变化的约束）进行了讨论。
The launching mechanism of the jets of active galactic nuclei is poorly constrained observationally, owing to the large distances to these objects and the very small scales (sub-parsec) involved. To better constrain theoretical models, it is especially important to get information from the region close to the physical base of the jet, where the plasma acceleration takes place. In this paper, we report multi-epoch and multifrequency continuum observations of the z = 2.5 blazar PKS 1830−211 with ALMA, serendipitously coincident with a strong γ-ray flare reported by Fermi-LAT. The blazar is lensed by a foreground z = 0.89 galaxy, with two bright images of the compact core separated by 1′′. Our ALMA observations individually resolve these two images (although not any of their substructures), and we study the change in their relative flux ratio with time (four epochs spread over nearly three times the time delay between the two lensed images) and frequency (between 350 and 1050 GHz, rest frame of the blazar), during the γ-ray flare. In particular, we detect a remarkable frequency-dependent behavior of the flux ratio, which implies the presence of a chromatic structure in the blazar (i.e., a core-shift effect). We rule out the possibility of micro- and milli-lensing effects and propose instead a simple model of plasmon ejection in the blazar’s jet to explain the time and frequency variability of the flux ratio. We suggest that PKS 1830−211 is likely to be one of the best sources to probe the activity at the base of a blazar’s jet at submillimeter wavelengths, thanks to the peculiar geometry of the system. The implications of the core shift in absorption studies of the foreground z = 0.89 galaxy (e.g., constraints on the cosmological variations of fundamental constants) are discussed.