We study the possibility of explaining the recent EDGES detection by an energy injection in the pre-recombination era. Our aim is to show that the residue of this energy injection could give the resultant increase in the energy density at frequencies $x_e \equiv h\nu/(kT) \simeq 10^{-3}$, which is needed to explain the EDGES result. We consider two models of energy injection: Gaussian profile with a fixed redshift of injection and radiative decay of a non-relativistic particle. We show that the energy injection should occur in the redshift range $z\lesssim 4 \times 10^3$ to prevent free-free processes from thermalizing the injected energy. The injected energy should be nearly 200--1000 times the CMB intensity at $x_e \simeq 10^{-3}$ to obtain the requisite residue. A large fraction of the injected energy gets thermalized and therefore distorts the CMB spectrum. We compute CMB spectral distortion for both the models and show that the fractional change in CMB energy density, $\Delta \rho_{\rm \scriptscriptstyle CMB}/\rho_{\rm \scriptscriptstyle CMB} \simeq 10^{-6}$, which might be detectable with the proposed experiment PIXIE. We also outline the implication of our proposed scenario for CMB anisotropies.

中文翻译：

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预复合时代的能量注入和EDGES检测

我们研究了在预重组时代通过能量注入来解释最近的 EDGES 检测的可能性。我们的目的是表明这种能量注入的残余可以在频率 $x_e \equiv h\nu/(kT) \simeq 10^{-3}$ 下导致能量密度的增加，这需要解释边缘结果。我们考虑两种能量注入模型：具有固定注入红移的高斯分布和非相对论粒子的辐射衰减。我们表明能量注入应该发生在红移范围 $z\lesssim 4 \times 10^3$ 内，以防止自由过程热化注入的能量。注入的能量应该是 $x_e \simeq 10^{-3}$ 处的 CMB 强度的近 200--1000 倍，以获得所需的残留物。大部分注入的能量被热化，因此扭曲了 CMB 光谱。我们计算了两个模型的 CMB 光谱失真，并表明 CMB 能量密度的分数变化 $\Delta \rho_{\rm \scriptscriptstyle CMB}/\rho_{\rm \scriptscriptstyle CMB} \simeq 10^{-6} $，这可能可以通过提议的实验 PIXIE 检测到。我们还概述了我们提出的 CMB 各向异性情景的含义。