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

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Galactic Center Milky Way

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In the current past, area objectives devoted to the research study of astrophysical signals in the high-energy spectrum exposed a series of enigmatic excesses not anticipated by the theoretical designs. In order to discover a description for these abnormalities, lots of services have actually been proposed. The most interesting hypothesis conjures up the contribution of the evasive dark matter, the mystical type of matter 4 times more plentiful than regular one and of which we have actually up until now discovered just its gravitational results. Two current theoretical research studies performed by Mattia di Mauro, scientist of the Turin department of INFN, among which was released in Physical Review D, verify that this description works with determined excesses, even more showing that it is not disproven by possible inconsistencies in between theoretical and observational information.

The results gotten are based upon an ingenious and refined analysis comparing information gotten in the last 11 years by the primary instrument aboard NASA’s Fermi, the Fermi Large Area Telescope (LAT), with measurements of other huge abnormalities tape-recorded by the orbiting Pamela detector and by the Alpha Magnetic Spectrometer experiment (AMS-02) aboard the International Space Station. Pamela and AMS are handled by worldwide partnerships in which INFN plays a definitive function.

Starting from 2009, the year in which Fermi measurements revealed a surplus of photons with energies equivalent to or higher than 1 GeV (2000 times the mass of an electron) originating from the center of our galaxy, the astrophysics neighborhood has actually attempted to describe the observations in numerous methods, consisting of the possible existence of countless weak pulsars near the stellar center and the possible gamma-ray contribution offered by dark matter. These analyses underwent excellent unpredictability given that they described designs of the so-called astrophysical gamma-ray background, produced by cosmic rays or by recognized sources, which, although efficient in consisting of a particular irregularity, undergo excellent mistake.

In order to explain the gamma-ray excess homes more exactly and to examine whether it is truly suitable with dark matter, the brand-new research study depended on the broadest set of information gathered in the in 2015 by the LAT, and utilized an analysis strategy that lessens the unpredictabilities of the astrophysical background by embracing numerous designs.

“The analysis methodology used,” discusses Mattia di Mauro, “has actually offered really pertinent info about the spatial circulation of excess gamma radiation, which can describe what produces the excess of high-energy photons in the Galactic center. If the excess was, for instance, brought on by the interaction in between cosmic rays and atoms, we would anticipate to observe its higher spatial circulation at lower energies and its lower diffusion at greater energies due to the proliferations of cosmic particles. My research study, on the other hand, highlights how spatial circulation of the excess does not alter as a function of energy. This element had actually never ever been observed prior to and might be discussed by dark matter existence dark matter analysis. This is since we believe the particles making up the dark matter halo need to have comparable energies. The analysis plainly reveals that the excess of gamma rays is focused in the Galactic center, precisely what we would anticipate to discover in the heart of the Milky Way if dark matter remains in reality a brand-new type of particle.”

A 2nd research study, which will be released in the exact same journal, takes a look at the credibility of the dark matter hypothesis utilizing the forecasts from a bigger design that explains possible particle interactions of this evasive element of deep space. A theoretical design showed how the presence of dark matter particles is not disproven by other abnormalities tape-recorded in the astrophysical background. These consist of the excess of positrons determined by Pamela and AMS-02, if credited to a surplus of dark matter, and the non-detection of high-energy photons from dwarf galaxies near to ours, whose excellent movements suggest the existence of high concentrations of dark matter.

“Starting from the physical model developed in this second study,” Di Mauro continues, “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 particles data.”

Reference: “Characteristics of the Galactic Center excess determined with 11 years of Fermi-LAT information” by Mattia Di Mauro, 22 March 2021, Physical Review D.
DOI: 10.1103/PhysRevD.103.063029