In the recent past, space missions dedicated to the study of astrophysical signals in the high-energy spectrum revealed a series of enigmatic excesses not predicted by the theoretical models. In order to find an explanation for these anomalies, many solutions have been proposed. The most exciting hypothesis invokes the contribution of the elusive dark matter, the mysterious form of matter four times more abundant than baryonic matter, and of which scientists have so far detected only gravitational effects.

Two recent theoretical studies carried out by Mattia di Mauro, researcher of the Turin division of INFN, one of which appeared today in Physical Review D, confirm that this explanation is compatible with measured excesses, further demonstrating that it is not disproven by potential discrepancies between theoretical and observational data. The results obtained are based on an innovative and refined analysis comparing data acquired in the last 11 years by the main instrument aboard NASA’s Fermi, the Fermi Large Area Telescope (LAT), with measurements of other astronomical anomalies recorded by the orbiting Pamela detector and by the Alpha Magnetic Spectrometer experiment (AMS-02) aboard the International Space Station. Pamela and AMS are managed by international collaborations in which INFN plays a decisive role.

Starting from 2009, the year in which Fermi measurements showed a surplus of photons with energies equal to or greater than 1 GeV (2000 times the mass of an electron) coming from the center of our galaxy, the astrophysics community has tried to explain the observations in several ways, including the possible presence of thousands of weak pulsars near the galactic center and the potential gamma-ray contribution provided by dark matter. These analyses were subject to great uncertainty since they referred to models of the so-called astrophysical gamma-ray background, produced by cosmic rays or by known sources, which, although capable of including a certain variability, are subject to great error.

Di Mauro says, “Starting from the physical model developed in this second study, after considering different results for the interaction and annihilation of dark matter particles, alternatives that would precede the production of high-energy photons, we verified which of these possibilities best accorded with the galactic center’s excess gamma rays, while also considering the surplus of positrons and the non-detection of gamma rays from dwarf galaxies. This comparison has made able to derive accurate properties of the dark matter, properties compatible with the galactic center excess and the upper limits found with other particle data.”

Provided by: INFN

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More information: Mattia Di Mauro. Characteristics of the Galactic Center excess measured with 11 years of Fermi -LAT dataPhysical Review D (2021). DOI: 10.1103/PhysRevD.103.063029

Multimessenger constraints on the dark matter interpretation of the Fermi-LAT Galactic center excess: arXiv:2101.11027v1 [astro-ph.HE]

Image Credit: ESO/FERMI-LAT