Free-Free Emission at Low Radio Frequencies
Free-Free Emission at Low Radio Frequencies
复制标题
低射频自由-自由发射
DOI：
10.1086/421241
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
S. Furlanetto
中科院分区：
文献类型：
--
作者：
A. Cooray;S. Furlanetto
我们讨论了星系际介质中电离气体的自由-自由射电发射。由于发射率与电子密度的平方成正比，平均背景对自由电子的空间聚集非常敏感。利用几个现有的电离气体团块模型，我们发现宇宙微波背景黑体光谱的预期自由-自由扭曲处于即将进行的实验（如宇宙学，天体物理学的绝对辐射计和漫射发射实验）可检测到的水平。然而，对畸变的主要贡献来自于z > 3处的团块气体，并且积分信号对再电离时代没有很强的约束。除了平均发射外，我们还考虑了自由-自由背景的空间波动，以及这些各向异性在多大程度上混淆了中性氢在再电离期间和之前的21厘米线发射波动的搜索。该背景在频率空间中是平滑的，因此可以通过频率差分去除，但前提是21厘米信号和自由-自由发射不相关。我们表明，由于自由-自由背景主要是在低红移时产生的，两个场之间的相互关系小于几个百分点。因此，多频清洗应是消除自由-自由混淆的有效途径。
We discuss free-free radio emission from ionized gas in the intergalactic medium. Because the emissivity is proportional to the square of the electron density, the mean background is strongly sensitive to the spatial clumping of free electrons. Using several existing models for the clumping of ionized gas, we find that the expected free-free distortion to the cosmic microwave background blackbody spectrum is at a level detectable with upcoming experiments such as the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission experiment. However, the dominant contribution to the distortion comes from clumpy gas at z ≲ 3, and the integrated signal does not strongly constrain the epoch of reionization. In addition to the mean emission, we consider spatial fluctuations in the free-free background and the extent to which these anisotropies confuse the search for fluctuations in 21 cm line emission from neutral hydrogen during and prior to reionization. This background is smooth in frequency space and hence can be removed through frequency differencing, but only so long as the 21 cm signal and the free-free emission are uncorrelated. We show that because the free-free background is generated primarily at low redshifts, the cross-correlation between the two fields is smaller than a few percent. Thus, multifrequency cleaning should be an effective way to eliminate the free-free confusion.
DOI：
10.1111/j.1365-2966.2003.07316.x
发表时间：
2003-09
影响因子：
4.8
作者：
Xuelei Chen;A. Cooray;N. Yoshida;N. Sugiyama
通讯作者：
Xuelei Chen;A. Cooray;N. Yoshida;N. Sugiyama