The most luminous far-infrared extragalactic sources

Abstract

Extremely luminous far-infrared sources are difficult to explain as active sites of star formation, because their ratios of optical-to-infrared luminosities are extremely low. It is shown that brief intervals during which interacting galaxies collide can account for extremely high (≥1011L_sun;) luminosities. The small fraction of the population that exhibits extreme luminosity also roughly equals the fraction of spiral galaxies expected to be observed undergoing collisions at any given time. The authors propose a number of potential tests that would distinguish this model from others.