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.
Highlights
Fermi-LAT has made a significant contribution to the study of high-energy gamma-ray diffuse emission and the observations of 3000 discrete sources
The GAMMA-400 energy range for gamma-ray studies is from ∼ 20 MeV to ∼ 1000 GeV
GAMMA-400 will have better angular and energy resolutions in the energy region 10–1000 GeV in comparison with current and future space- and ground-based instruments (VERITAS [7], MAGIC [8], H.E.S.S. [9], CTA [10], and HAWC [19] (Figs. 5, 6) and will allow us to fill the gap at energies of ∼ 100 GeV between the spaceand ground-based instruments
Summary
Analysis of gamma-ray results according to the Fermi-LAT and ground-based telescope data. Three catalogs of gamma-ray sources have been published based on the Fermi-LAT observational results: 1FGL [1] and 2FGL [2] for the energy range from 100 MeV to 100 GeV, 3FGL [3] for the energy range from 100 MeV to 300 GeV. Two catalogs of high-energy gamma-ray sources were published: 1FHL [4] for energies above 10 GeV and 2FHL [5] for the energy range of 50 GeV–2 TeV. Based on results of gamma-ray observations at energies above 100 GeV by ground-based facilities VERITAS [7] MAGIC [8] H.E.S.S. Note that the energy resolution of Fermi-LAT and ground-based facilities is only 10–15% at energies of 10–300 GeV. Much better angular resolution is required in order to identify many gamma-ray sources
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