NGC326—a radio galaxy with a precessing beam?
NGC326—a radio galaxy with a precessing beam?
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DOI：
10.1038/276588a0
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发表时间：
1978-12
期刊：
影响因子：
64.8
通讯作者：
Rd Ekers;R. Fanti;C. Lari;P. Parma
中科院分区：
文献类型：
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作者：
Rd Ekers;R. Fanti;C. Lari;P. Parma
来自最强烈的河外源的射电辐射集中在一个穿过相关星系的波段上，并与之对称。这种结构有时被修改为V形或C形，星系位于顶端，如3C465（参考文献2）等广角尾源，偶尔也会出现更极端的尾源伸长，如NGC1265（参考文献3）。在一些源中，可以看到s形或180°对称。这首先是在Cen a1的外部组件中注意到的，一个更好的例子是3C272.1（参考文献5,6）。在更高分辨率的观测中发现了S失真非常明显的其他来源（例如Cyg a7和3C478）。在这些模型中，所讨论的结构与中心有一个小角度，它们给人一种梁型模型的强烈印象，其中梁晃动或进动了几度。作为对从B2星表中选出的低光度射电星系进行系统研究的一部分，科学家发现了一个新的射电源，其结构具有180°对称，但不是S型。进光束模型的投影似乎为这种奇怪的形状提供了一个自然的解释，并在这里进行了描述。
THE radio emission from most strong extragalactic sources is concentrated in a band which passes through, and is symmetrical with respect to, the associated galaxy1. This structure is sometimes modified to a V or C shape with the galaxy at the apex, as in the wide angle tail sources like 3C465 (ref. 2), and occasionally to the more extreme elongation of the tail sources such as NGC1265 (ref. 3). In a few sources an S-shaped or 180° symmetry is seen. This was first noted in the outer components of Cen A4and a better example is 3C272.1 (refs 5, 6). Other sources where the S distortion is very clear have been found with higher resolution observations (for example Cyg A7and 3C478). In these, the structure in question subtends a small angle from the centre and they give a strong impression of a beam type of model in which the beam has wobbled or precessed by a few degrees9. A new example of a radio source showing a structure with a 180° symmetry, but not of the S form, has been found as part of a systematic study of radio galaxies of lower luminosity selected from the B2 catalogue10. The projection of a precessing beam model seems to provide a natural explanation for this strange shape and is described here.