May 2020 • 2020NatAs...4..467A
Abstract • Luminous and ultraluminous infrared galaxies have been an active area of galaxy research since their discovery more than three decades ago. With its vast increase in sensitivity in the infrared, Spitzer played a major role in exploring these galaxies in the local Universe, and at high redshifts. In this Review, we highlight some of the discoveries made with the Infrared Spectrograph on Spitzer, through observations of luminous and ultraluminous infrared galaxies to cosmic noon. These include measuring the role of starbursts and actively accreting supermassive black holes as power sources, finding evidence for energetic feedback on the atomic and molecular interstellar gas and dust and identifying the physical properties of luminous infrared galaxies on and off the galaxy star-forming main sequence. Finally, we briefly discuss how future infrared telescopes will build upon the discoveries of Spitzer to better understand the evolution of this important population since the epoch of reionization.