The circumnuclear starburst ring in infrared ultraluminous galaxies

Ultraluminous infrared galaxies (ULIRGs), powered by starburst activity and often with supermassive black holes accreting material at their nuclei, contain large reservoirs of molecular gas. This is to be expected: Molecular gas is the raw material for new stars and moreover the presence of the infrared luminous warm dust implies an abundance of molecular gas. Galaxy collisions often trigger star formation activity and simulations reveal that as the two galaxies merge their gas tends to fall tow...