In the 1980s when Infrared Astronomical Satellite (IRAS) was scanning the sky, it came across a few bright sources in the Infrared wavelength, which were too faint to be detected in previous optical surveys. These galaxies were classified as Infrared galaxies. Luminous Infrared galaxies (LIRGs), as the name suggests, are characterized by a prodigious amount of emission at infrared (IR) wavebands. The bulk infrared emission in these galaxies is due to warm dust heated by active galactic nuclei, starbursts, or both. These galaxies hence provide a unique laboratory to do a comprehensive study of star formation and AGN activity.
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