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arXiv 1808.02897astro-ph.COastro-ph.HEhep-ph
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红移$z\lesssim 2\times 10^5$的高能粒子级联非热相对论CMB光谱畸变的丰富结构

Rich structure of non-thermal relativistic CMB spectral distortions from high energy particle cascades at redshifts $z\lesssim 2\times 10^5$

Sandeep Kumar Acharya, Rishi Khatri

备注：
updated to match the published version
发表信息：
Phys. Rev. D 99, 043520 (2019)
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摘要：

一般认为，对于复合前的能量注入，所有注入的能量在重子光子等离子体中以热的形式耗散，从而在CMB谱中产生$y$型、$i$型和$μ$型畸变。我们表明，这种假设是不正确的，当能量注入的形式充满活力（即能量远大于背景CMB温度）的粒子。我们进化的电磁级联，从注入的高能粒子，在膨胀的宇宙，并遵循CMB光谱失真的非热分量的电磁簇射与背景光子，电子和离子的相互作用所产生的。在簇射中的粒子的能量已经退化到足够低的能量以使它们可以与背景等离子体热化之前，电磁簇射将其能量的相当大一部分损失到CMB光谱失真。这种光谱畸变是簇射中的非热高能电子与CMB相互作用的结果，因此具有与$y$型或$i$型畸变基本不同的形状。最终的\emph{non-thermal relativistic}（$ntr$型）CMB光谱畸变的形状取决于注入的电子、正电子和光子的初始能谱，因此具有关于能量注入机制的信息，例如衰变或湮灭的暗物质粒子的衰变或湮灭通道。光谱畸变的形状对能量注入的红移也很敏感。我们的计算打开了一个新的窗口，在$z\lesssim 2\times 10^5$的能量注入，这是不简并，并可以区分从低红移热$y$型扭曲。

英文摘要：

It is generally assumed that for energy injection before recombination, all of the injected energy is dissipated as heat in the baryon-photon plasma, giving rise to the $y$-type, $i$-type, and $μ$-type distortions in the CMB spectrum. We show that this assumption is incorrect when the energy is injected in the form of energetic (i.e. energy much greater than the background CMB temperature) particles. We evolve the electromagnetic cascades, from the injection of high energy particles, in the expanding Universe and follow the non-thermal component of CMB spectral distortions resulting from the interaction of the electromagnetic shower with the background photons, electrons, and ions. The electromagnetic shower loses a substantial fraction of its energy to the CMB spectral distortions before the energy of the particles in the shower has degraded to low enough energies that they can thermalize with the background plasma. This spectral distortion is the result of the interaction of non-thermal energetic electrons in the shower with the CMB and thus has a shape that is substantially different from the $y$-type or $i$-type distortions. The shape of the final \emph{non-thermal relativistic} ($ntr$-type) CMB spectral distortion depends upon the initial energy spectrum of the injected electrons, positrons, and photons and thus has information about the energy injection mechanism e.g. the decay or annihilation channel of the decaying or annihilating dark matter particles. The shape of the spectral distortion is also sensitive to the redshift of energy injection. Our calculations open up a new window into the energy injection at $z\lesssim 2\times 10^5$ which is not degenerate with, and can be distinguished from the low redshift thermal $y$-type distortions.

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