Searching for Integrated Sachs-Wolfe Effect from Fermi-LAT diffuse γ-ray map
Abstract
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 . 8 σ confidence level, and the significance would be increased to 2 . 7 σ 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 Aamp = 0 . 95 ± 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 ΛCDM 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.
- Publication:
-
Physics of the Dark Universe
- Pub Date:
- September 2020
- DOI:
- 10.1016/j.dark.2020.100585
- arXiv:
- arXiv:2005.03833
- Bibcode:
- 2020PDU....2900585T
- Keywords:
-
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted for publication in Physics of the Dark Universe