恒星形成星系的宇宙Gamma-Ray背景
Cosmic Gamma-Ray Background from Star-Forming Galaxies
摘要：
河外伽马射线背景的起源是一个紧迫的宇宙学之谜。费米伽马射线太空望远镜最近测量了这种背景的强度和光谱;两者都与以前的测量结果有很大的不同。我们提出了一种新的计算正常恒星形成星系的伽马射线背景。与长期以来的预期相反，我们发现，许多但单独微弱的正常星系可能包括大部分的费米信号，而不是罕见的，但本质上明亮的活动星系。这一结果具有广泛的意义，包括：用伽马射线探测宇宙恒星形成历史的可能性;推断宇宙射线和银河磁场的宇宙学演化的能力;以及从稀有来源（例如，暗物质团块）通过它们的大的各向异性。
英文摘要：
The origin of the extragalactic gamma-ray background is a pressing cosmological mystery. The Fermi Gamma-Ray Space Telescope has recently measured the intensity and spectrum of this background; both are substantially different from previous measurements. We present a novel calculation of the gamma-ray background from normal star-forming galaxies. Contrary to long-standing expectations, we find that numerous but individually faint normal galaxies may comprise the bulk of the Fermi signal, rather than rare but intrinsically bright active galaxies. This result has wide-ranging implications, including: the possibility to probe the cosmic star formation history with gamma rays; the ability to infer the cosmological evolution of cosmic rays and galactic magnetic fields; and an increased likelihood of identifying subdominant components from rare sources (e.g., dark matter clumps) through their large anisotropy.
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