Clusters of galaxies are enriched with positrons from jets of active galactic nuclei (AGNs) or from the interaction of cosmic rays with the intracluster gas. We follow the cooling of these positrons and show that their eventual annihilation with cluster electrons yields a narrow annihilation line. Unlike annihilation in the interstellar medium of galaxies, the line produced in clusters is not smeared by three-photon decay of positronium, because positronium formation is suppressed at the high (>~ 1 keV) temperature of the cluster electrons. We show that if AGN jets are composed of e^+e^- pairs, then the annihilation line from rich clusters within a distance of 100 Mpc might be detectable with future space missions, such as INTEGRAL or EXIST.
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机译：来自活跃银河核（AGN）射流或宇宙射线与团簇内气体相互作用的正电子富集了星系团。我们跟踪了这些正电子的冷却过程，并证明了它们最终被团簇电子an灭时会产生一条狭窄的line灭线。与星系星际介质中的an灭不同，在簇中产生的谱线不会被正电子的三光子衰减所拖尾，因为在簇电子的高（>〜1 keV）温度下正电子的形成受到抑制。我们表明，如果AGN喷气机由e ^ + e ^-对组成，那么未来的太空任务（例如INTEGRAL或EXIST）可能会检测到100 Mpc距离内的富星团的line灭线。
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