Dark Matter Is the Most Likely Source of Excess of Gamma Rays From Galactic Center of the Milky Way

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 4 times more abundant than ordinary one and of which we have so far detected only its gravitational effects. Two recent theoretical studies carried out by Mattia di Mauro, researcher of the Turin division of INFN, one of which was published 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.

In order to describe the gamma-ray excess properties more precisely and to evaluate whether it is really compatible with dark matter, the new study relied on the broadest set of data collected in the last year by the LAT, and used an analysis technique that minimizes the uncertainties of the astrophysical background by adopting multiple models.

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