In cooperation with researchers from the National Research Nuclear University MEPhI, an international collaboration of astrophysicists has recently discovered a signal of high-energy galactic photons within the framework of Fermi experiment.
This discovery may shed some light on the origin of high-energy neutrinos discovered earlier by the IceCube Neutrino Observatory at the Amundsen-Scott Station. The researchers’ announcement was published in the journal Physical Review-D.
Neutrinos pass through matter where other particles cannot. For example, solar neutrinos that originate from the depths of the Sun provide scientists with information on the thermonuclear reactions taking place in the solar core. The high-energy neutrinos that researchers have recorded originate from unknown extraterrestrial objects, and they provide information that is not yet accessible via other observation methods.
Together with their colleagues from the Paris Diderot University (France), Norwegian University of Science and Technology and University of Geneva (Switzerland), MEPhI researchers have discovered a new counterpart in the gamma-ray flux upon studying the data obtained with the help of the Fermi Gamma-ray Space Telescope for high-energy (over 300 GeV) observations.
“At energy higher than 300 GeV, signals emitted by sources outside our galaxy are significantly suppressed by the attenuation in the intergalactic medium,” said Dmitry Semikoz, Professor at MEPhI and one of the authors of the research study. “Within the galaxy, however, gamma radiation is rarely absorbed, suggesting that the source of this new component must be located within our galaxy.”
The new component’s spectrum is very much in line with the abnormally high neutrino flux recently discovered within the framework of the IceCube experiment, Semikoz stated. Considering that neutrinos are always produced together with gamma rays, which have a similar spectrum, the scientists suggested that both spectrums share the same origin.
“In our research, we came up with two models serving as possible explanations,” the professor said. “In the first model, neutrinos and gamma rays are produced as a result of cosmic ray interaction, and originate from a region of the galaxy close to us. The second model suggests that the neutrinos and gamma rays were produced as a result of dark matter decay processes taking place in our galaxy.”
Scientists will now try to determine which model is correct by further studying the heterogeneity of the signal. If the signal is caused by dark matter decay processes, the study will prove to be highly important. But even if the other model, suggesting the presence of a close astrophysical source. proves to be correct, for the first time ever, we might just have a chance to find a cosmic ray source that produces the observed neutrino and gamma radiation.
Russian researchers are currently building an underwater Gigaton Water Detector neutrino telescope at the bottom of Lake Baikal, Russia. The new telescope has a volume of one cubic kilometre. By 2020, it will have the same sensitivity as the IceCube Observatory. Located in the Northern Hemisphere, it is equipped for observing the central part of our galaxy better than the IceCube Observatory (considering those neutrino researchers working in the Antarctic have to literally observe particles “through the Earth”).