An Edge-brightened Bicone in the Nuclear Regions of Cygnus A
An Edge-brightened Bicone in the Nuclear Regions of Cygnus A
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天鹅座 A 核区的边缘亮化双锥体
DOI：
10.1086/311882
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
W. Sparks
中科院分区：
文献类型：
--
作者：
C. Tadhunter;C. Packham;D. Axon;N. Jackson;J. Hough;A. Robinson;S. Young;W. Sparks
利用哈勃空间望远镜上的近红外照相机和多目标摄谱仪，对原型的强射电星系天鹅座A进行了波长范围为0.8-2.35微米的连续成像观测。在2.25 μm处，图像主要由核点源（FWHM < 0.″21）的存在所控制，其通量比先前基于地面的研究所推导出的极限小约4倍。观测还揭示了一个以点源为中心的边缘增亮的双锥结构，这与在年轻恒星周围观察到的结构惊人地相似。双锥相对于射电轴的高偏振和取向使我们得出结论，它是一个被照亮的结构，而边缘增亮则提供了证据，证明双锥是由核区域的流出物定义的，就像照明类星体辐射场的极图一样。我们的观测结果进一步表明，并非所有的核辐射场的各向异性都是由圆环面中小于100 pc尺度的消光引起的;一些各向异性必须由尘埃带中1 kpc尺度的吸收和散射产生。
Infrared-imaging observations that span the wavelength range of 0.8-2.35 μm have been obtained for the archetypal powerful radio galaxy Cygnus A using the Near-Infrared Camera and Multiobject Spectrograph on board the Hubble Space Telescope. At 2.25 μm, the images are dominated by the presence of a nuclear point source (FWHM < 0.″21), whose flux is a factor of ~4 times less than the limits deduced from previous ground-based studies. The observations also reveal an edge-brightened biconical structure centered on the point source, which is strikingly similar to those observed around young stellar objects. The high polarization and orientation of the bicone relative to the radio axis lead us to conclude that it is an illuminated structure, while the edge brightening provides evidence that the bicone is defined as much by outflows in the nuclear regions as by the polar diagram of the illuminating quasar radiation field. A further implication of our observations is that not all of the anisotropy in the nuclear radiation field is caused by extinction on a scale less than 100 pc in the torus; some of the anisotropy must be generated by absorption and scattering in the dust lane on a 1 kpc scale.