Influence of synchrotron self-absorption on 21-cm experiments
Influence of synchrotron self-absorption on 21-cm experiments
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同步加速器自吸收对21厘米实验的影响
DOI：
10.1111/j.1365-2966.2012.21234.x
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发表时间：
2012-05
影响因子：
4.8
通讯作者：
Xu, Haiguang
中科院分区：
文献类型：
--
作者：
Wu, Xiang-Ping;Gu, Jun-Hua;Wang, Jingying;Xu, Haiguang
河外射电源的同步辐射自吸收产生的光谱曲率会破坏光谱的平滑特性。这导致了这样一个前提，即在寻找再电离(EOR)纪元的21厘米实验中，明亮的射电前景可以成功地消除。我们给出了河外射电源同步自吸收产生的谱曲率对低频天空角功率谱测量的影响的定量估计。我们将一个唯象模型引入到10°×10°的小天空区域的模拟射电源中，该模型的特征是具有100-1000 MHz范围内的射电源的分数(F)和关于在νm附近的频谱跃迁的破坏的幂定律。我们统计地比较了去掉 mJy的亮源后，考虑和不考虑河外射电源的同步辐射自吸收后，它们的残差图的变化。此外，每个像素的频域中的最佳拟合多项式被减去。结果表明，同步加速器自吸收对提高采收率探测的影响敏感地依赖于转换频率νm附近射电源的频谱分布。用谱折射率在νm转换的破缺幂定律描述的硬跃迁模型将在残留背景上留下明显的印记，从而与宇宙提高采收率信号严重混淆。然而，河外前景的角功率谱上的光谱特征可以被拟合，并因此通过使用多项式在可接受的程度上被减去(δT<；1 mk)，该光谱特征是由软转变模型生成的，在该软转变模型中，光谱分布的上升和下降幂规律通过在特征宽度上跨越200 Mhz的平稳转变而联系在一起。由于后一种情况似乎在理论预期和射电光谱观测中都是有利的，我们得出结论，在21厘米的实验中，同步加速器自吸收对河外射电源的污染可能很小。
The presence of spectral curvature resulting from the synchrotron self-absorption of extragalactic radio sources could break down the spectral smoothness feature. This leads to the premise that the bright radio foreground can be successfully removed in 21-cm experiments that search for the epoch of reionization (EoR). We present a quantitative estimate of the effect of the spectral curvature resulting from the synchrotron self-absorption of extragalactic radio sources on the measurement of the angular power spectrum of the low-frequency sky. We incorporate a phenomenological model, which is characterized by the fraction (f) of radio sources with turnover frequencies in the range of 100–1000 MHz and by a broken power law for the spectral transition around the turnover frequencies νm, into simulated radio sources over a small sky area of 10° × 10°. We compare statistically the changes in their residual maps with and without the inclusion of the synchrotron self-absorption of extragalactic radio sources after the bright sources of mJy are excised. Furthermore, the best-fitting polynomials in the frequency domain on each pixel are subtracted. It has been shown that the effect of synchrotron self-absorption on the detection of the EoR depends sensitively on the spectral profiles of the radio sources around the turnover frequencies νm. A hard transition model, described by the broken power law with the turnover of spectral index at νm, would leave pronounced imprints on the residual background and would therefore cause serious confusion with the cosmic EoR signal. However, the spectral signatures on the angular power spectrum of the extragalactic foreground, generated by a soft transition model in which the rising and falling power laws of the spectral distribution around νm are connected through a smooth transition spanning ≥200 MHz in a characteristic width, can be fitted and consequently subtracted by the use of polynomials to an acceptable degree (δT < 1 mK). As this latter scenario seems to be favoured in both theoretical expectations and radio spectral observations, we conclude that the contamination of extragalactic radio sources by synchrotron self-absorption in 21-cm experiments is probably very minor.
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影响因子：
5
作者：
J. Pritchard;A. Loeb
通讯作者：
J. Pritchard;A. Loeb
DOI：
10.1146/annurev-astro-081309-130936
发表时间：
2009-10
影响因子：
33.3
作者：
M. Morales;J. Wyithe
通讯作者：
M. Morales;J. Wyithe
DOI：
10.1111/j.1365-2966.2012.21065.x
发表时间：
2012-01
影响因子：
4.8
作者：
E. Chapman;F. Abdalla;G. Harker;G. Harker;V. Jeli'c;P. Labropoulos;P. Labropoulos;S. Zaroubi
通讯作者：
E. Chapman;F. Abdalla;G. Harker;G. Harker;V. Jeli'c;P. Labropoulos;P. Labropoulos;S. Zaroubi
DOI：
10.1111/j.1365-2966.2011.18276.x
发表时间：
2010-10
影响因子：
4.8
作者：
Nada Petrovic;S. Peng Oh
通讯作者：
Nada Petrovic;S. Peng Oh
DOI：
10.1086/429857
发表时间：
2004-08
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Mário G. Santos;A. Cooray;L. Knox
通讯作者：
Mário G. Santos;A. Cooray;L. Knox