各向同性无线电背景的再认识
The isotropic radio background revisited
摘要：
我们提出了一个广泛的分析确定的各向同性无线电背景。我们考虑六种不同的无线电地图，范围从22 MHz到2.3 GHz，覆盖了天空的很大一部分。大尺度辐射被建模为各向同性分量加上银河系同步辐射和热韧致辐射的线性组合。点状源和扩展源要么被屏蔽，要么通过模板来解释。我们发现一个强大的各向同性无线电背景的估计，有限的不同的银河系模型之间的散射。各向同性背景的水平明显高于通过整合观测到的河外源的数量计数所获得的贡献。由于各向同性分量在高纬度地区占主导地位，因此使总发射的轮廓平坦，这种过量的银河系起源似乎不太可能。我们的结论是，除非一个系统的偏移存在于地图中，并提供我们目前的理解银河同步辐射是合理的，远低于目前的实验阈值的河外源似乎占河外射电天空的亮度的大部分。
英文摘要：
We present an extensive analysis on the determination of the isotropic radio background. We consider six different radio maps, ranging from 22 MHz to 2.3 GHz and covering a large fraction of the sky. The large scale emission is modeled as a linear combination of an isotropic component plus the Galactic synchrotron radiation and thermal bremsstrahlung. Point-like and extended sources are either masked or accounted for by means of a template. We find a robust estimate of the isotropic radio background, with limited scatter among different Galactic models. The level of the isotropic background lies significantly above the contribution obtained by integrating the number counts of observed extragalactic sources. Since the isotropic component dominates at high latitudes, thus making the profile of the total emission flat, a Galactic origin for such excess appears unlikely. We conclude that, unless a systematic offset is present in the maps, and provided that our current understanding of the Galactic synchrotron emission is reasonable, extragalactic sources well below the current experimental threshold seem to account for the majority of the brightness of the extragalactic radio sky.
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