Drexel physicists produce new images of the Milky Way




Black sky with blue and white dust streak in the center representing the Milky Way




IceCube Collaboration/US National Science Foundation (Lily Le & Shawn Johnson)/ESO (S. Brunier)


The Milky Way is made visible through the emission of optical frequencies of electromagnetic radiation – previously fleeting to the naked eye – this magical phenomenon has now been captured in a new ‘picture’ of the galaxy, making it more accessible to the eye than ever before. Drexel University physics researchers at the IceCube Neutrino Observatory led the production of the unique image by determining the galactic origin of thousands of neutrinos (tiny astronomical “ghost particles”) that typically pass through the Earth undetected despite their existence in large quantities. The composition of the first neutrino-based image of the Milky Way uses particles of matter instead of the usual electromagnetic energy.

The findings were achieved by a collaboration of researchers led by Naoko Kurahashi Neilson, PhD, an associate professor of physics at Drexel’s College of Arts and Sciences, using the IceCube Neutrino Observatory supported by the US National Science Foundation at the Amundsen Station- Scott South Pole of NSF in Antarctica and published in Science.

The mammoth IceCube Neutrino Observatory detects nearly imperceptible particles – high-energy neutrinos – from space using thousands of light sensors in a network buried deep within a cubic kilometer of Antarctic ice to the bottom of the Southern Ocean, a 2,450 meters deep or similar to a stack of five Empire State Building.

With an NSF Faculty Early Career Development grant, Kurahashi Neilson and Michael Richman, then a postdoctoral researcher at Drexel, proposed innovative computational analysis β€” using new machine learning techniques and developing better methods for filtering data β€” to generate the image.

“We use neutrinos to study the universe, in a way that we can’t study light,” said Kurahashi Neilson. “At the outset of this research, we expected to see a completely different universe using neutrinos, like using night vision goggles to see in the dark.”

In the Milky Way, cosmic rays (high-energy protons and heavier nuclei) interact with galactic gas and dust to produce both gamma rays and neutrinos. Kurahashi Neilson and colleagues noted that they expected the Milky Way to be a source of high-energy neutrinos due to observing gamma rays from the galactic plane, the plane where most of a galaxy’s mass is located.

“The community has long understood that our galaxy is an essentially guaranteed source of high-energy neutrinos,” Richman said. produced in the earth’s atmosphere. Since then, the team has improved every aspect of the approach, leading to the compelling result that we can finally share today.”

The IceCube Neutrino Observatory detects the interactions — a faint pattern of light — of neutrinos beneath the ice. But the challenge is determining where the neutrinos come from. Some patterns are highly directional and can point to a particular area of ​​the sky, which allows researchers to determine the source of the neutrinos. Other interactions are harder to decipher because they produce fuzzy “balls of light” cascading through the clear ice.

Steve Sclafani, a former Drexel PhD student, developed a machine learning algorithm that compared the relative position, size and energy of more than 60,000 neutrino-generated light falls recorded by the IceCube over 10 years, 30 times more events than the selection used in a previous analysis of the galactic plane using cascade events.

After testing and verifying the algorithm, the research team plugged in actual data provided by IceCube from neutrinos determined to come from the southern sky, where they expect most neutrino emissions from the galactic plane to be near the center of the Via. milky. The identified neutrinos were then compared to previously published “prediction maps” of locations in the sky where the Milky Way’s neutrinos should shine, theoretically produced in places where the observed gamma rays were thought to be the byproducts of collisions between cosmic and interstellar gas.

Using real IceCube data in the algorithm resulted in an image showing bright dots corresponding to locations in the Milky Way.

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Image Source : drexel.edu

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