The above image shows a combined view of Hickson Compact Group (HGC) 22 as seen by the Spitzer Space Telescope at wavelengths of 3.6, 4.5, and 8 microns. These compact groups of galaxies provide a rich environment in which to study the effect of galaxy interactions and mergers on galaxy formation and evolution. In this image, a red color is indicative of vigorous star formation activity, while blue light reflects an older population of dormant stars.

U.Va. prof. Kelsey Johnson led this research program to study a sample of 12 compact groups of galaxies using infrared light, and she is part of a team that is observing thest compact groups from radio wavelengths to the X-ray. Graduate students Amy Reines and Lisa May Walker are also involved in the project.