A University of Oklahoma team has detected for the first time the most luminous gamma-ray emission from a galaxy—the merging galaxy Arp 220 is the nearest ultraluminous infrared galaxy to soil, and it reveals the hidden extreme energetic processes in galaxies. The first gamma-ray detection of an ultraluminous infrafred galaxy occurs when the most energetic cosmic rays collide with the interstellar medium causing these galaxies to glow—expanding observations of these galaxies to the highest energy ranges. Luminous infrared galaxies and ultraluminous infrared galaxies—many of them the product of mergers between galaxies—are the most luminous of all galaxies.
Source: phys.org