Luminous infrared galaxy

A galaxy with total infrared luminosity between 10¹¹ and 10¹² times the Sun’s luminosity. Its infrared output is usually powered by intense star formation, an active galactic nucleus, or both.

Infrared astronomy: The study of celestial objects through infrared radiation, which reveals cool material and light reprocessed by dust. Its observing methods detect the dust-reprocessed energy that defines these galaxies.
Luminosity: The total energy an object emits per unit time across all wavelengths. The category is set by a threshold in total infrared luminosity.
Cosmic star-formation history: The changing rate at which the universe formed stars over cosmic time. Luminous infrared galaxies trace star formation hidden from optical surveys, especially at earlier epochs.
Normal galaxy: A galaxy whose overall properties fall within the common range for its population and epoch. Its infrared output is generally less extreme than that of a luminous infrared galaxy.
Interstellar dust: Small solid particles between stars that absorb, scatter, and emit electromagnetic radiation. Dust absorbs much of the visible and ultraviolet light from young stars and reradiates it in the infrared.
Infrared: Electromagnetic radiation with wavelengths longer than visible light and shorter than microwaves. The infrared band carries the energy used to classify these galaxies.
Galaxy merger: An interaction in which galaxies collide and combine under gravity. Mergers can compress gas and trigger the intense activity seen in many nearby examples.
Dust-obscured galaxy: A galaxy whose ultraviolet and optical light is heavily attenuated by dust, often with strong infrared emission. Dust obscuration can describe a galaxy’s appearance without requiring this specific luminosity range.
Starburst galaxy: A galaxy forming stars at a rate far above the typical rate for galaxies of comparable mass. Concentrated star formation heats dust and can dominate a luminous infrared galaxy’s energy output.
Blackbody radiation: Electromagnetic radiation emitted by an idealized object whose spectrum depends only on its temperature. Warm dust emits a thermal spectrum that helps shape a galaxy’s infrared output.

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