Cross-correlation of the extragalactic gamma-ray background with the thermal Sunyaev-Zel’dovich effect in the cosmic microwave background
Cross-correlation of the extragalactic gamma-ray background with the thermal Sunyaev-Zel’dovich effect in the cosmic microwave background
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DOI：
10.1103/physrevd.101.103022
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发表时间：
2020-05
影响因子：
5
通讯作者：
Masato Shirasaki;O. Macias;S. Ando;S. Horiuchi;Naoki Yoshida
中科院分区：
文献类型：
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作者：
Masato Shirasaki;O. Macias;S. Ando;S. Horiuchi;Naoki Yoshida
星系团中的宇宙射线是对宇宙中大尺度结构运行的高能过程的独特探测。星系团中宇宙线的精确测量对于提高我们对团内介质（ICM）中非热成分的理解以及宇宙学分析中星系团质量估计的准确性至关重要。本文利用河外γ射线背景和宇宙微波背景中的热Sunyaev-Zel'dovich（tSZ）效应进行了互相关分析。预期的互相关信号将包含丰富的信息，宇宙射线诱导的伽马射线发射在最大质量的星系团在$z\sim0.1-0.2$。我们分析了伽马射线背景图与8年的数据所采取的费米卫星上的大面积望远镜和公开可用的tSZ图普朗克。我们确认，测得的互相关是一致的零检测，因此，它使我们能够把最严格的约束宇宙射线质子的加速效率在冲击和周围的星系团。我们发现，在2 sigma置信水平下，当星系团的流体静力质量偏差为30%时，加速效率必须小于5%，且流体静力质量偏差对我们的结果没有显著影响.我们的约束意味着ICM中的非热宇宙射线压力只能引入$\le 3\%$水平的流体静力学质量偏差，强调宇宙射线本身并不能解释普朗克分析所推断的质量偏差。最后，我们讨论了切伦科夫望远镜阵列未来的可探测性前景的宇宙射线诱导伽马射线从英仙座集群。
Cosmic rays in galaxy clusters are unique probes of energetic processes operating with large-scale structures in the Universe. Precise measurements of cosmic rays in galaxy clusters are essential for improving our understanding of non-thermal components in the intracluster-medium (ICM) as well as the accuracy of cluster mass estimates in cosmological analyses. In this paper, we perform a cross-correlation analysis with the extragalactic gamma-ray background and the thermal Sunyaev-Zel'dovich (tSZ) effect in the cosmic microwave background. The expected cross-correlation signal would contain rich information about the cosmic-ray-induced gamma-ray emission in the most massive galaxy clusters at $z\sim0.1-0.2$. We analyze the gamma-ray background map with 8 years of data taken by the Large Area Telescope onboard Fermi satellite and the publicly available tSZ map by Planck. We confirm that the measured cross-correlation is consistent with a null detection, and thus it enables us to put the tightest constraint on the acceleration efficiency of cosmic ray protons at shocks in and around galaxy clusters. We find the acceleration efficiency must be below 5\% with a $2\sigma$ confidence level when the hydrostatic mass bias of clusters is assumed to be 30\%, and our result is not significantly affected by the assumed value of the hydrostatic mass bias. Our constraint implies that the non-thermal cosmic-ray pressure in the ICM can introduce only a $\le 3\%$ level of the hydrostatic mass bias, highlighting that cosmic rays alone do not account for the mass bias inferred by the Planck analyses. Finally, we discuss future detectability prospects of cosmic-ray-induced gamma rays from the Perseus cluster for the Cherenkov Telescope Array.