The Sunyaev–Zel'dovich effect

Abstract

The Sunyaev-Zel'dovich e ect causes a change in the apparent brightness of the Cosmic Microwave Background Radiation towards a cluster of galaxies or any other reservoir of hot plasma. Measurements of the e ect provide distinctly di erent information about cluster properties than X-ray imaging data, while combining X-ray and Sunyaev-Zel'dovich e ect data leads to new insights into the structures of cluster atmospheres. The e ect is redshift-independent, and so provides a unique probe of the structure of the Universe on the largest scales. The present review discusses the theory of the Sunyaev-Zel'dovich e ect and collects published results for many clusters, presents the overall conclusions that may bedrawn from the detections so far, and discusses the prospects for future research on the Sunyaev-Zel'dovich e ects.Subject headings: Sunyaev-Zel'dovich E ect; Clusters; Microwave Background Radiation Astrophysical ContextCompton scattering is one of the major physical processes that couples matter and radiation. Its importance is often stressed in highly relativistic environments where large energy transfers occur: for example, in the synchrotron self-Compton process that may beresponsible for much of the X-radiation from active galactic nuclei (e.g., Fabian et al. 1986). However, the Compton process also has observable consequences in low-energy environments, where small energy transfers occur. The Sunyaev-Zel'dovich e ect, which arises from the scattering of electrons in clusters of galaxies on the cosmic microwave 1 Also Smithsonian Institution Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, USA { 2 { background radiation eld, is perhaps the most important astrophysical example. The e ect provides a cosmological probe, it has been used to measure the properties of gas in clusters of galaxies, and it has been discussed as a means of measuring the motions of clusters of galaxies and hence studying the evolution of structure in the Universe.The purpose of this review is to provide a comprehensive introduction to the SunyaevZel'dovich e ect. I aim to provide both a theoretical treatment that can befollowed by non-specialists, and an introduction to the observation of the e ect with a critical review of data in the literature. The latter is more di cult today than it would have been ve years ago because of the rapid increase in the number of papers on the Sunyaev-Zel'dovich e ect, and the improvement i n t h e quality o f t h e results that are being gained.

Observations of the Sunyaev–Zel'dovich effect at high angular resolution towards the galaxy clusters A665, A2163 and CL0016+16

“…This cluster is the highest redshift object detected with the SZ effect in the millimetric domain. Our result of y 0 = 3.20 ± 0.78 × 10 −4 is larger than but compatible with the central parameter y 0 = 2.18 × 10 −4 (h/0.5) −1/2 predicted by Birkinshaw [11] using ROSAT Xray data (within 1.3σ). It is in agreement with the SZ radio determination of Hughes and Birkinshaw [27] with a larger beam (1.8' with a 7' beam throw) of y 0 = 2.20 ± 0.37 × 10 −4 (see also [8]), and more marginally with the SZ map of the interferometer experiment of Carlstrom [13] of y 0 = 1.31 ± 0.12 × 10 −4 , which spans 1 to 10' angular scales.…”

Cosmological parameters

“…The result from the first cluster for which sufficiently detailed data was available, A665 (at z = 0.182), was h = (0.4 − 0.5) ± 0.12 [13]; combining this with data on A2218 (z = 0.171) raised this somewhat to h = 0.55 ± 0.17 [12]. The history and more recent data have been reviewed by Birkinshaw [14], who concludes that the available data give a Hubble parameter h ≈ 0.6 with a scatter of about 0.2. But since the available measurements are not independent, it does not follow that h = 0.6 ± 0.1; for example, there is a selection effect that biases low the h determined this way.…”

Integrated Sachs-Wolfe effect versus redshift test for the cosmological parameters

“…Voids would simply be expanding with the background and the ISW effect would be determined by the time-delay contribution alone [22]. The ISW-z test might be more fruitfully applied to cosmic voids than galaxy clusters because it is very sensitive to cluster accretion (see below) and the CMB temperature seen through a cluster is contaminated by hot gas emissions from the cluster itself and from other secondary anisotropies such as the Sunyaev-Zeldovich (SZ) effect [46,47].…”