Physicists from the Baikal-GVD collaboration have caught galactic neutrinos with energies above 200 teraelectronvolts. The sources of these neutrinos were most likely in the Milky Way. The article was published in The Astrophysical Journal.
Neutrinos are currently considered one of the most difficult objects to observe: they hardly interact with matter. At the same time, cosmic neutrinos provide information about the most extreme phenomena in the Universe, from stellar explosions to the activity of galactic nuclei. In recent years, large neutrino observatories, including IceCube in Antarctica, have reported recording extremely high-energy neutrinos, but most of these events appear to have occurred outside the Milky Way. Until now, the contribution of our Galaxy to the recorded astrophysical component of neutrinos remained unclear, and various theoretical estimates differed greatly.
Researchers from the Baikal-GVD collaboration have detected high-energy neutrinos, most likely originating from within our galaxy. The scientists used the Baikal-GVD neutrino telescope, a large-scale system of optical modules suspended on vertical cables in the clear waters of Lake Baikal. Each module contains a photodetector for recording Cherenkov radiation, which occurs when high-energy particles fly by. Physicists use it to track flashes of light in the water and use this data to reconstruct the direction and energy of the neutrinos.
Scientists analyzed events with reconstructed energies above 200 teraelectronvolts, registered during the six-year operation of the telescope. Physicists saw eight such events in total. Scientists noticed that the average angle of deviation of these events from the galactic equator was significantly smaller than expected from a uniform distribution across the sky. The probability of a random coincidence was estimated as 1.4×10-2. The authors also compared the Baikal-GVD results with new open IceCube data and found a similar picture in both cases. In a joint analysis of all neutrino events, the error probability dropped to 3.4×10-4.
According to the physicists, this result suggests that the galactic contribution to the high-energy neutrino flux may be more noticeable than previously assumed. A more detailed study, in particular the search for point sources of neutrinos in star-forming regions, will require larger statistics and continued observations. Baikal-GVD continues to increase the volume of the detector and will be able to provide even more convincing data in the coming years.
Earlier, another Cherenkov detector of a similar type, KM3NeT, saw a neutrino of ultra-high energy (several tens of petaelectronvolts), read about this in our article “Didn’t expect it?”