High-Energy Neutrino Emission from the Milky Way Unveiled by IceCube

The Milky Way, our celestial home, is a breathtaking spectacle in the night sky, a hazy belt of stars stretching from one horizon to the other. The IceCube Neutrino Observatory has recently made an unprecedented breakthrough, capturing an image of the Milky Way using neutrinos, microcosmic spectral heralds. The IceCube Collaboration, an international team of over 350 scientists, will publish a paper on June 30 in the Science journal, revealing evidence of high-energy neutrino emission from the Milky Way.

An artist’s composition of the Milky Way seen through a neutrino lens (blue). Credit: IceCube Collaboration/U.S. National Science Foundation (Lily Le & Shawn Johnson)/ESO (S. Brunier)

The IceCube Neutrino Observatory, stationed at the Amundsen-Scott South Pole Station, is a colossal detector bankrolled by the National Science Foundation (NSF) and further supported by 14 countries hosting members of the IceCube Collaboration. With energies millions to billions of times higher than those created by stellar fusion reactions, high-energy neutrinos have been detected by this unique detector equipped with over 5,000 light sensors. IceCube is tasked with detecting signs of high-energy neutrinos from our galaxy and reaching out to the most remote corners of the universe. Interactions between cosmic rays, high-energy protons, heavier nuclei (also produced in our galaxy), and galactic dust and gas invariably generate gamma rays and neutrinos.

The research has primarily targeted the southern sky, where the majority of these subatomic particles' emission from the galactic plane near our galaxy's center is anticipated. The background of muons and neutrinos created by cosmic ray interactions with Earth's atmosphere, however, has presented significant obstacles. To counter these, IceCube collaborators at Drexel University have designed analyses that select "cascade" events, or neutrino interactions in ice that lead to approximately spherical light showers. The selection of cascade events has enhanced the sensitivity to neutrinos in the southern sky by reducing the contamination of muons and atmospheric neutrinos.

The crucial breakthrough was the application of machine learning methods by IceCube collaborators at TU Dortmund University. These methods enhanced the identification of neutrino-produced cascades and their direction and energy reconstruction. The study utilized a dataset of 60,000 neutrinos, collected over a decade from IceCube data, a 30-fold increase from the selection used in an earlier galactic plane analysis. The neutrinos were compared with prediction maps highlighting expected neutrino emission spots in the galaxy. The IceCube team plans on tackling further challenges in their upcoming analyses.

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