Search for line-like and box-shaped spectral features from nearby galaxy clusters with 11.4 years of Fermi LAT data

Abstract

Sharp spectral structures in the γ-ray band are an important dark matter (DM) signature. Previously, a tentative line feature at ∼ 43 GeV is reported in 16 nearby galaxy clusters (GCls) with 7.1 years of Fermi -LAT data, whose TS value is ∼ 16.7. In this work, we search for line signals and box-shaped structures using the stacked data from those 16 GCls with 11.4-yr P8R3 data. There is still a hint at ∼ 42 GeV, dominated by the radiation of Virgo and Ophiuchus clusters. Though the TS value was high up to 21.2 in October 2016, currently it has dropped to 13.1. Moreover, the TS value at ∼ 42 GeV decreases to 2.4 when the EDISP2 data are excluded from the analysis. Consequently, we do not find any statistically significant line-like signal and then set up the 95% confidence level upper limits on the thermally averaged cross section of DM annihilating into double photons. The same line search has been carried out for an alternative GCl sample from the Two Micron All-Sky Survey but no any evidence has been found. We also search for box-shaped features in those 16 baseline GCls.No signal is found as well and the corresponding upper limits on the annihilation cross section are given.

Search for gamma-ray line signals around the black hole at the galactic center with DAMPE observation

“…A tentative line was found at ∼43 GeV in the Fermi-LAT observation of 16 nearby galaxy clusters, with a global significance of 3.0σ [18]. Although the line is found to have a strange temporal behavior of its significance [20], the interesting possibility of a signal from DM annihilation has not The 95% confidence level upper limits on the DM cross section σv χχ→γγ in the BH spike scenario. The black lines are results based on a slidingwindow unbinned analysis, which is commonly used in the searches for gamma-ray lines.…”

“…This line signal is thought to be the smoking gun of a new physics since normal astrophysical processes are not expected to generate this signal. With the gamma-ray data from EGRET [3], Fermi-LAT [4], and the Dark Matter Particle Explorer (DAMPE) [5], line-like signals have been widely studied for various searching targets [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Tentative line signals have also been reported from the galactic center (GC) [8,9] or galaxy clusters [18,20], although a robust detection is still absent.…”

“…With the gamma-ray data from EGRET [3], Fermi-LAT [4], and the Dark Matter Particle Explorer (DAMPE) [5], line-like signals have been widely studied for various searching targets [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Tentative line signals have also been reported from the galactic center (GC) [8,9] or galaxy clusters [18,20], although a robust detection is still absent. The non-detection often leads to strict constraints on the annihilation cross section or the lifetime of DM annihilation / decay into double photons.…”