Cosmic infrared background

The cosmic infrared background is the accumulated infrared emission from distant galaxies, integrated across cosmic history. It records energy absorbed by dust and re-emitted as infrared light.

Cosmic optical background: The accumulated optical and ultraviolet light from stars and galaxies across cosmic history. It traces starlight that escapes dust, complementing the infrared energy dust reradiates.
Cosmic star formation history: The changing rate at which the universe converted gas into stars over cosmic time. Dust-reprocessed starlight makes the infrared background an integrated record of this history.
Infrared source counts: Measurements of the number of astronomical sources detected at different infrared fluxes. Counts test whether resolved galaxies can account for the measured background intensity.
Cosmic infrared background anisotropy: Spatial variation in the intensity of the cosmic infrared background across the sky. Its patterns reveal how contributing galaxies cluster and how much emission remains unresolved.
Interstellar dust: Small solid particles between stars that absorb, scatter, and emit electromagnetic radiation. Dust converts much of the absorbed starlight from distant galaxies into infrared emission.
Galaxy formation and evolution: The processes by which galaxies assemble, change, and acquire their observed properties over time. Evolving galaxies supply the sources whose infrared emission accumulates into the background.
Herschel Space Observatory: The European Space Agency observatory that conducted far-infrared and submillimeter astronomy from 2009 to 2013. Its surveys resolved many dusty galaxies contributing to the background.
Cosmic infrared background fluctuations: Variations in cosmic infrared background intensity after subtracting detected sources and foregrounds. Residual fluctuations constrain the abundance and clustering of faint contributors.
Cosmological redshift: The stretching of light to longer wavelengths as the universe expands. Expansion shifts galaxies’ emitted infrared spectra before they contribute to the observed background.
Luminous infrared galaxy: A galaxy emitting most of its energy in the infrared, with infrared luminosity above 10¹¹ solar luminosities. These dusty, active galaxies contribute strongly to the background’s bright infrared output.

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