GeV GAMMA-RAY FLUX UPPER LIMITS FROM CLUSTERS OF GALAXIES
GeV GAMMA-RAY FLUX UPPER LIMITS FROM CLUSTERS OF GALAXIES
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DOI：
10.1088/2041-8205/717/1/l71
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发表时间：
2010-07-01
影响因子：
7.9
通讯作者：
Ziegler, M.
中科院分区：
文献类型：
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作者：
Ackermann, M.;Ajello, M.;Ziegler, M.
探测到与星系团相关的弥散射电发射表明，相对论轻子群正在注入星系团内介质(ICM)。这些电子和正电子要么直接注入ICM并在其中加速，要么通过宇宙射线离子散射周围的质子而产生二次电子对。涉及高能轻子的辐射机制，以及由强子相互作用产生的中性介子的衰变，都有可能产生丰富的GeV光子。在这里，我们报告了使用费米伽马射线空间望远镜上的大面积望远镜从2008年8月到2010年2月收集的数据来寻找星系团的GeV辐射。33个星系团是根据它们的邻近和高质量、X射线流量和温度以及非热活动的迹象而被选中进行这项研究的。考虑到高能辐射的点状模型和空间分辨模型，我们报道了一个观察到的团簇样本(典型值(1-5)×10(-9)光子厘米(-2)S(-1))在0.2GeV-100GeV范围内的光子通量上限，并讨论了这些结果如何约束ICM中高能轻子和强子的特征以及磁场。体积平均相对论-强子-热能密度比为
The detection of diffuse radio emission associated with clusters of galaxies indicates populations of relativistic leptons infusing the intracluster medium (ICM). Those electrons and positrons are either injected into and accelerated directly in the ICM, or produced as secondary pairs by cosmic-ray ions scattering on ambient protons. Radiation mechanisms involving the energetic leptons together with the decay of neutral pions produced by hadronic interactions have the potential to produce abundant GeV photons. Here, we report on the search for GeV emission from clusters of galaxies using data collected by the Large Area Telescope on the Fermi Gamma-ray Space Telescope from 2008 August to 2010 February. Thirty-three galaxy clusters have been selected according to their proximity and high mass, X-ray flux and temperature, and indications of non-thermal activity for this study. We report upper limits on the photon flux in the range 0.2-100 GeV toward a sample of observed clusters (typical values (1-5) x 10(-9) photon cm(-2) s(-1)) considering both point-like and spatially resolved models for the high-energy emission and discuss how these results constrain the characteristics of energetic leptons and hadrons, and magnetic fields in the ICM. The volume-averaged relativistic-hadron-to-thermal energy density ratio is found to be