Sunyaev–Zeldovich effect

The Sunyaev–Zeldovich effect (named after Rashid Sunyaev and Yakov B. Zeldovich and often abbreviated as the SZ effect) is the spectral distortion of the cosmic microwave background (CMB) through inverse Compton scattering by high-energy electrons in galaxy clusters, in which the low-energy CMB photons receive an average energy boost during collision with the high-energy cluster electrons.

Observed distortions of the cosmic microwave background spectrum are used to detect the disturbance of density in the universe.

The distortion of the CMB resulting from a large number of high energy electrons is known as the thermal Sunyaev–Zeldovich effect.

[2] Comparing Sunyaev–Zeldovich and X-ray data can also be used to determine the Hubble constant using the angular diameter distance of the cluster.

[3] These thermal distortions can also be measured in superclusters and in gases in the local group, although they are less significant and more difficult to detect.

In superclusters, the effect is not strong (< 8 μK), but with precise enough equipment, measuring this distortion can give a glimpse into large-scale structure formation.

Hydrodynamic structure formation simulations are being studied to gain data on thermal and kinetic effects in the theory.

[5] Observations are difficult due to the small amplitude of the effect and to confusion with experimental error and other sources of CMB temperature fluctuations.

The use of surveys of clusters detected by their Sunyaev–Zeldovich effect for the determination of cosmological parameters has been demonstrated by Barbosa et al. (1996).

[2] Instruments built specifically to study the effect include the Sunyaev–Zeldovich camera on the Atacama Pathfinder Experiment,[9] and the Sunyaev–Zeldovich Array, which both saw first light in 2005.

In 2012, the Atacama Cosmology Telescope (ACT) performed the first statistical detection of the kinematic SZ effect.