The innermost region of the water megamaser radio galaxy 3C 403
The innermost region of the water megamaser radio galaxy 3C 403
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水巨型微波射电星系3C 403的最内部区域
DOI：
10.1051/0004-6361:20078317
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发表时间：
2007
影响因子：
6.5
通讯作者：
Weiss A.
中科院分区：
文献类型：
--
作者：
Tarchi A;Brunthaler A;Henkel C;Menten K.M;Braatz J;Weiss A.
活动星系核的标准统一方案要求存在高柱密度的气体和尘埃，这些气体和尘埃可能会掩盖中心引擎。到目前为止，对射电星系进行的直接亚弧秒分辨率的研究还很少。本文的目的是阐明典型的x形Fanaroff-Riley II型射电星系3C 403的核环境，这是已知唯一拥有H2O超级激光的强大射电星系。方法采用very Large Array A-array和单碟Green Bank和Effelsberg 1.3 cm测量仪定位和监测水激微波发射。采用超长基线干涉测量法（Very Long Baseline Interferometry）进行6 cm连续体观测，在更小尺度上分析核环境的空间结构，而使用IRAM 30 m望远镜观测COJ= 1-0和2-1跃迁，以寻找空间扩展的中等密度气体组分的热发射。结果H2O脉泽特征与核心连续发射的位置在5mas （5.5 pc）以内重合。（各向同性）光度有时超过1000的两个主脉泽分量的强度似乎是反相关的，具有典型的一年强烈变化的时间尺度。如果这些变化是云固有的，则隐含的角源大小为0.3 mas，亮度温度为510 K。VLBI连续体观测支持这样一种情况，即核心由主要的中央射电连续体组成，伴随着一个喷流和反喷流，指向星系的西部和东部大尺度叶。CO仍然未被检测到，提供最大尺度尺寸为~ 50pc (500k /Tb)1/2，其中tb表示COJ= 1-0线的亮度温度。概述了可能产生观测到的脉泽发射的可能情况。核发动机的质量为108倍，观测到的脉泽特征只能用NGC 4258中的吸积盘来解释，如果它们仅仅代表系统速度分量的话。然而，没有看到假定的脉泽盘的后退和接近部分，并且观测到的特征的长期速度漂移（尚）不明显。最有可能的是，这两个主脉泽部件标志着与核喷流相互作用的激波分子气体。射电星系的x形形态可能指向一个双核引擎。这种可能性使3C 403的核环境大为复杂化，应促使进行一些有价值的后续研究。
ContextThe standard unified scheme of active galactic nuclei requires the presence of high column densities of gas and dust potentially obscuring the central engine. So far, few direct subarcsecond resolution studies of this material have been performed toward radio galaxies.AimsThe goal of this paper is to elucidate the nuclear environment of the prototypical X-shaped Fanaroff-Riley type II radio galaxy 3C 403, the only powerful radio galaxy known to host an H2O megamaser.MethodsVery Large Array A-array and single-dish Green Bank and Effelsberg 1.3 cm measurements were performed to locate and monitor the water maser emission. Very Long Baseline Interferometry 6 cm continuum observations were taken to analyze the spatial structure of the nuclear environment at even smaller scales, while the COJ= 1–0 and 2–1 transitions were observed with the IRAM 30-m telescope to search for thermal emission from a spatially extended, moderately dense gas component.ResultsPositions of the H2O maser features and the continuum emission from the core coincide within 5 mas (5.5 pc). Intensities of the two main maser components with (isotropic) luminosities sometimes surpassing 1000 appear to be anti-correlated, with typical timescales for strong variations of one year. If the variations are intrinsic to the cloud(s), the implied angular source size would be 0.3 mas and the brightness temperature 510 K. The VLBI continuum observations support a scenario where a nuclear core, represented by the dominant central radio continuum component, is accompanied by a jet and counterjet, directed toward the western and eastern large scale lobes of the galaxy. CO remains undetected, providing a maximum scale size of ~50 pc (500 K/Tb)1/2, withTbdenoting the brightness temperature of the COJ= 1–0 line. Possible scenarios that could produce the observed maser emission are outlined. Adopting a mass of several 108for the nuclear engine, the observed maser features can only be interpreted in terms of an accretion disk as in NGC 4258, if they solely represent the systemic velocity components. The receding and approaching parts of the putative maser disk are, however, not seen and a secular velocity drift of the observed features is not (yet) apparent. Most likely, the two main maser components mark shocked molecular gas interacting with the nuclear jets. The X-shaped morphology of the radio galaxy may point at a binary nuclear engine. This possibility, greatly complicating the nuclear environment of 3C 403, should motivate a number of worthwhile follow-up studies.
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影响因子：
6.5
作者：
T. Wiklind;C. Henkel
通讯作者：
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影响因子：
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作者：
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通讯作者：
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影响因子：
8.7
作者：
S. Baum;T. Heckman;W. Breugel
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DOI：
10.1086/374924
发表时间：
2003
期刊：
The Astrophysical Journal
影响因子：
--
作者：
A. Peck;C. Henkel;J. Ulvestad;A. Brunthaler;H. Falcke;M. Elitzur;K. Menten;J. Gallimore
通讯作者：
J. Gallimore
塞弗特星系中的中性氢（21 厘米）吸收：自由-自由吸收和亚千秒差距气态盘的证据
DOI：
10.1086/307853
发表时间：
1999
期刊：
The Astrophysical Journal
影响因子：
--
作者：
J. Gallimore;S. Baum;C. O’Dea;A. Pedlar;E. Brinks
通讯作者：
E. Brinks