The Sunyaev-Zel'dovich effect
(often abbreviated as the SZ effect
) is the result of 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 CMB 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, where the CMB photons interact with electrons that have high energies due to their temperature
- kinematic effects, a second-order effect where the CMB photons interact with electrons that have high energies due to their bulk motion (also called the Ostriker-Vishniac effect, after Jeremiah P. Ostriker and Ethan Vishniac.)
Rashid Sunyaev and Yakov 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, and on 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.
Timeline of observations
- Birkinshaw; et al. (1984). "The Sunyaev-Zel'dovich effect towards three clusters of galaxies". Nature 309 34–35.
- Birkinshaw, Mark (1999). "The Sunyaev Zel'dovich Effect". Physics Reports 310 97.
- Cen, Renyue; Jeremiah P. Ostriker (1994). "A hydrodynamic approach to cosmology: the mixed dark matter cosmological scenario". The Astrophysical Journal 431 1.
- Hu, Jian; Yu-Qing Lou 0402669. | title = Magnetic Sunyaev-Zel'dovich effect in galaxy clusters | journal = ApJL}}
- Ma, Chung-Pei; J. N. Fry "Nonlinear Kinetic Sunyaev-Zel'dovich Effect". PRL 0106342. }}
- Myers, A. D.; et al. "Evidence for an Extended SZ Effect in WMAP Data". Astrophysics 0306180. }}
- Rephaeli, Y. (1995). "Comptonization Of The Cosmic Microwave Background: The Sunyaev-Zeldovich Effect". Annual Review of Astronomy and Astrophysics 33 541–580.
- Springel, Volker; Martin White and Lars Hernquist 0008133. | title = Hydrodynamic Simulations of the Sunyaev-Zel'dovich effect(s) | journal = ApJ}}
- Sunyaev, R. A.; Ya. B. Zel'dovich (1970). "Small-Scale Fluctuations of Relic Radiation". Astrophysics and Space Science 7 3.
- Sunyaev, R. A.; Ia. B Zel'dovich (1980). "Microwave background radiation as a probe of the contemporary structure and history of the universe". Annual review of astronomy and astrophysics 18 537–560.
- Diego, J.M; E. Martinez, J.L. Sanz, N. Benitez, J. Silk (2002). "The Sunyaev-Zel'dovich effect as a cosmological discriminator". Monthly Notices of the Royal Astronomical Society, 331 556–568.
- Royal Astronomical Society, Corrupted echoes from the Big Bang? RAS Press Notice PN 04/01