Sunyaev–Zel'dovich effect

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The Sunyaev–Zel'dovich effect is a distortion of the cosmic microwave background caused when its photons scatter from energetic electrons, especially in the hot gas within clusters of galaxies.

In the thermal effect, inverse Compton scattering transfers energy from hot electrons to microwave-background photons. This produces a characteristic decrease in brightness at lower microwave frequencies and an increase at higher frequencies.

A kinetic form of the effect is caused by the bulk motion of the scattering gas relative to the cosmic microwave background. It produces a smaller frequency shift linked to the cluster's line-of-sight velocity.

Because the effect depends on integrated electron pressure rather than ordinary surface brightness, it is a powerful way to detect and study distant galaxy clusters. It is used to estimate cluster masses, gas properties, cosmic structure, and cosmological parameters.

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• Source / publisher: Wikipedia
• URL type: WWW
• Credits: Wikipedia
• URL: https://en.wikipedia.org/wiki/Sunyaev–Zel'dovich_effect