Iowa State researchers contribute to discovery of gamma rays from starburst galaxy

AMES, Iowa - Iowa State University astrophysicists contributed to the recent discovery that a galaxy quickly creating new stars is also a source of high energy gamma rays.

The discovery has just been published by the journal Nature. The study reports that researchers using the VERITAS array of four telescopes at the Fred Lawrence Whipple Observatory in Arizona have detected gamma rays of a trillion electron volts coming from the M 82 galaxy. The corresponding author of the article is Wystan Benbow of the Harvard-Smithsonian Center for Astrophysics and the Whipple Observatory.

Researchers discovered cosmic rays (mostly hydrogen nuclei) from space nearly a century ago and have developed theories about their origins in supernova remnants and star-forming galaxies, but hadn't found evidence to support those theories.

"This is a step toward solving a 100-year-old puzzle in cosmic ray physics," said Frank Krennrich, an Iowa State professor of physics and astronomy and a collaborator on the VERITAS project.

Gamma rays are high energy electromagnetic radiation. The rays discovered by the VERITAS researchers have a trillion times the energy of visible light. M 82 is a galaxy in the direction of the Ursa Major constellation that's 12 million light years from Earth. It is classified as a starburst galaxy. Such galaxies are colliding with other galaxies, causing shockwaves that compress gases and create stars at very high rates.

"What this shows is that there is a strong connection between a galaxy with high star formation, high gas density and the production of cosmic rays," Krennrich said.

But Krennrich said there's more work to be done to definitively trace gamma rays to cosmic rays in starburst galaxies.

Researchers believe more knowledge of gamma rays could help them explore distant regions of space, help them look for evidence of dark matter, determine how much electromagnetic radiation the universe has produced and answer questions about the formation of stars and galaxies.