Sunyaev-Zel'dovich effect

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The Sunyaev-Zel'dovich effect (occasionally abbreviated as the SZ effect) is due to high energy electrons distorting the cosmic microwave background radiation (CMB) through inverse Compton scattering, in which some of the energy of the electrons is transferred to the low energy photons. Observed distortions of the cosmic microwave background spectrum are used to detect the density perturbations of the universe. Using the Sunyaev-Zel'dovich effect, dense clusters of galaxies have been observed.

The Sunyaev-Zel'dovich effect can be divided into:

• thermal effects
• kinetic effects
• polarization

Sunyaev and Zel'dovich predicted the effect, and conducted research in 1969, 1972, and 1980. The Sunyaev-Zel'dovich effect is of major astrophysical and cosmological interest. It can help determine the value of the Hubble constant. To distinguish the SZ effect due to galaxy clusters from ordinary density perturbations, both the spectral dependence and the spatial dependence of fluctuations in the cosmic microwave background are used. Analysis of CMB data at higher angular resolution (high l values) requires taking into account the Sunyaev-Zel'dovich effect.

Current research is focused on modelling how the effect is generated by the intra-cluster plasma in galaxy clusters redshifts, in using the effect to estimate the Hubble constant and to separate different components in the angular average statistics of fluctuations in the background. Hydrodynamic structure formation simulations are being studied to gain data on thermal and kinetic effects in the theory. Observations are difficult due to the small amplitude of the effect and to confusion with experimental error and other sources of CMB temperature fluctuations. However, since the Sunyaev-Zel'dovich effect is a scattering effect, its magnitude is independent of redshift. This is very important: it means that clusters at high redshift can be detected just as easily as those at low redshift. Another factor which facilitates high-redshift cluster detection is the angular scale versus redshift relation: it changes little between redshifts of 0.3 and 2, meaning that clusters between these redshifts have similar sizes on the sky.

Measurements of the SZ effect

• 1983 - Researchers from the Cambridge Radio Astronomy Group and the Owens Valley Radio Observatory first detect the Sunyaev-Zel'dovich effect from clusters of galaxies.
• 1993 - The Ryle Telescope begins regular observations of the Sunyaev-Zel'dovich effect from clusters of galaxies
• 2003 - The WMAP satellite maps the Cosmic Microwave Background (CMB) over the whole sky with some (limited) sensitivity to the Sunyaev-Zel'dovich effect
• 2005 - The Arcminute Microkelvin Imager and the Sunyaev-Zel'dovich Array each begin surveys for very high redshift clusters of galaxies using the Sunyaev-Zel'dovich effect
• 2006 - The Atacama Cosmology Telescope (ACT) will begin an SZ survey of galaxy clusters
• 2007 - The South Pole Telescope will start searching for clusters using SZ observations

See also

• Background radiation
• Compton effect
• Cosmic background radiation
• Cosmic microwave background radiation
• Rashid Sunyaev
• Yakov Zel'dovich

External links and references

• Birkinshaw et al, The Sunyaev-Zel'dovich effect towards three clusters of galaxies Nature, Vol. 309, May 3, p. 34, 35, 1984.
• Myers et al, "Evidence for an Extended SZ Effect in WMAP Data". 2004 RAS Press Release Images.
  • Myers, A. D., T. Shanks, P. J. Outram, W. J. Frith, and A. W. Wolfendale, "Evidence for an Extended SZ Effect in WMAP Data". Astrophysics, astro-ph/0306180.
• Birkinshaw, Mark, "The Sunyaev Zel'dovich Effect", Department of Physics, University of Bristol, Bristol, UK.
• Ma, Chung-Pei, and J. N. Fry, "Nonlinear Kinetic Sunyaev-Zel'dovich Effect". PRL. May 27 2002. (arXiv.org)
• Sunyaev, R. A. and Ya. B. Zel'dovich, "Small-Scale Fluctuations of Relic Radiation". Astrophysics and Space Science, Vol. 7, p.3, 1970.
• Sunyaev, R. A.; Zel'dovich, Ia. B. "Microwave background radiation as a probe of the contemporary structure and history of the universe". Annual review of astronomy and astrophysics. Volume 18. Palo Alto, California. 1980.
• Hu, Jian, and Yu-Qing Lou, "Magnetic Sunyaev-Zel'dovich effect in galaxy clusters". ApJL.
• "Matter-antimatter asymmetry". Phys199 course. hep.caltech.edu (PDF)
• Cen, Renyue, and Jeremiah P. Ostriker, "A hydrodynamic approach to cosmology: the mixed dark matter cosmological scenario". The Astrophysical Journal, 431, (1994), 1.
• Springel, Volker, Martin White, and Lars Hernquist, "Hydrodynamic Simulations of the Sunyaev-Zel'dovich effect(s)". ApJ.
• Royal Astronomical Society. "Corrupted echoes from the Big Bang?". RAS Press Notice PN 04/01.