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arXiv 2005.03833astro-ph.CO
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从Fermi-LAT弥散$γ$射线图寻找积分Sachs-Wolfe效应

Searching for Integrated Sachs-Wolfe Effect from Fermi-LAT Diffuse $γ$-ray Map

Xiu-Hui Tan, Ji-Ping Dai, Jun-Qing Xia

摘要:

本文估计了普朗克2018年宇宙微波背景(CMB)温度各向异性图与费米大天区望远镜(LAT)9年观测数据中未分辨的$γ$射线背景(UGRB)之间的互相关功率谱。在这个分析中,我们使用了多达9个能源箱在一个广泛的能量范围内的[0.631,1000] GeV的费米-LAT UGRB数据。首先,我们发现能量范围为[1.202,2.290] GeV和[17.38,36.31] GeV的费米数据在$1.8σ$置信水平下显示了积分萨克斯-沃尔夫(ISW)效应的正向证据,并且当这两个能量区间一起使用时,显著性将增加到$2.7σ$。其次,我们采用单次幂律模型对振幅进行归一化,并利用所有九个费米能级来衡量ISW效应的显著性,得到了${\rm A_{amp}}=0.95 \pm 0.53$($68\%$ C.L.)。在稳健性检验中,我们通过随机化9个能箱的费米模拟图实现零假设,得到未检测到ISW效应,证实了ISW信号来自Fermi-LAT扩散$γ$射线数据,与标准$Λ$ CDM模型预测基本一致。我们使用互相关系数来显示不同能量仓之间的关系。此外,我们改变了费米图掩模上银道面的切割范围$|b|$,并仔细检查了由此对ISW信号检测的影响。

英文摘要:

In this paper, we estimate the cross-correlation power spectra between the Planck 2018 cosmic microwave background (CMB) temperature anisotropy map and the unresolved $γ$-ray background (UGRB) from the 9-years Fermi-Large Area Telescope (LAT) data. In this analysis, we use up to nine energy bins over a wide energy range of [0.631, 1000] GeV from the Fermi-LAT UGRB data. Firstly, we find that the Fermi data with the energy ranges [1.202, 2.290] GeV and [17.38, 36.31] GeV show the positive evidence for the Integrated Sachs-Wolfe (ISW) effect at $1.8σ$ confidence level, and the significance would be increased to $2.7σ$ when using these two energy bins together. Secondly, we apply the single power-law model to normalize the amplitude and use all the nine Fermi energy bins to measure the significance of the ISW effect, we obtained ${\rm A_{amp}}=0.95 \pm 0.53$ ($68\%$ C.L.). For the robustness test, we implement a null hypothesis by randomizing the Fermi mock maps of nine energy bins and obtain the non-detection of ISW effect, which confirms that the ISW signal comes from the Fermi-LAT diffuse $γ$-ray data and is consistent with the standard $Λ$CDM model prediction essentially. We use a cross-correlation coefficient to show the relation between different energy bins. Furthermore, we vary the cut ranges $|b|$ of galactic plane on the mask of Fermi map and carefully check the consequent influence on the ISW signal detection.

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