New stage in high-energy gamma-ray studies with GAMMA-400 after Fermi-LAT

Abstract

Abstract. Fermi-LAT has made a significant contribution to the study of high-energy gamma-ray diffuse emission and the observations of 3000 discrete sources. However, one third of all gamma-ray sources (both galactic and extragalactic) are unidentified, the data on the diffuse gamma-ray emission should be clarified, and signatures of dark matter particles in the high-energy gamma-ray range are not observed up to now. GAMMA-400, the currently developing gamma-ray telescope, will have angular (∼ 0.01• at 100 GeV) and energy (∼ 1% at 100 GeV) resolutions in the energy range of 10-1000 GeV which are better than Fermi-LAT (as well as ground gamma-ray telescopes) by a factor of 5-10. It will observe some regions of the Universe (such as the Galactic Center, Fermi Bubbles, Crab, Cygnus, etc.) in a highly elliptic orbit (without shading the telescope by the Earth) continuously for a long time. It will allow us to identify many discrete sources, to clarify the structure of extended sources, to specify the data on the diffuse emission, and to resolve gamma rays from dark matter particles.

A potentially detectable gamma-ray line in the Fermi Galactic center excess — in light of one-step cascade annihilations of secluded (vector) dark matter via the Higgs portal

“…In the parameter plane of the DM annihilation cross section and DM mass, that is relevant to the spectral line(s) generated from the Higgs portal one-step cascade annihilation of DM, we will further show the current bounds imposed by the Fermi-LAT observations of dwarf spheroidal galaxies (dSphs) [40], by Fermi-LAT gamma-ray line search in the region around the GC [41], by the Planck cosmic microwave background (CMB) [2], and by direct detections [42,43]. The Fermi-LAT projected sensitivity with as much as 15 years of data [44] as well as the high energy resolution detectors from forthcoming experiments [45][46][47] is capable of exploring the considered parameter space. Thus, the Higgs portal scenario is very likely to be testable in the near future.…”

“…10 -6 (see figures 2 and 4). As shown in figure 4, the observed spectral line width is very sensitive to the boost of S. For further comparison with the effect due to the energy resolution of the instrument, we consider a higher energy resolution of ξ =2%, which would be achievable in the DAMPE [45] and GAMMA-400 [46,47] experiments, and show the results in figure 5.…”