Sunyaev-Zel'dovich Effect Applications in Cosmology
Summary
The Sunyaev-Zel’dovich (SZ) effect—the distortion of the cosmic microwave background (CMB) through inverse Compton scattering by free electrons—has become an indispensable tool in modern cosmology. Its thermal component (tSZ) probes the pressure of hot intracluster gas, enabling measurements of cluster masses, pressure profiles and baryon fractions that are largely redshift-independent. The kinetic component (kSZ) arises from bulk motions of ionised gas, offering a means to trace cosmic velocity fields and thereby constrain large-scale structure growth. SZ observations, when combined with X-ray and gravitational lensing data, calibrate cluster scaling relations and feedback models, while cross-correlations with galaxy surveys map the spatial distribution of baryons relative to dark matter. On smaller angular scales, measurements of the tSZ power spectrum inform models of non-thermal pressure support, star formation and active galactic nuclei feedback. The kSZ signal from the epoch of reionisation encodes information on patchiness and timing of the first ionising sources. High-resolution maps of the Compton-y parameter unlock studies of filamentary gas beyond cluster virial radii and provide critical foreground separation for primordial CMB studies. Together, tSZ and kSZ techniques furnish independent constraints on cosmological parameters such as σ8 and Ωm, deepen our understanding of baryonic physics in galaxy formation, and offer a unique window onto the thermal and dynamical state of the Universe from low to high redshift.
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Sunyaev-Zel'dovich Effect Applications in Cosmology publication trend
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Technical terms
Thermal SZ effect: Spectral distortion of the CMB due to scattering off hot, thermal electrons in galaxy clusters, quantified by the Compton-y parameter.
Kinetic SZ effect: Frequency-independent CMB temperature shift induced by the bulk motion of free electrons relative to the CMB rest frame.
Compton-y parameter: Line-of-sight integral of electron pressure, representing the amplitude of the thermal SZ distortion.
Pairwise kSZ power spectrum: Statistical measure of correlated kSZ temperature fluctuations between galaxy pairs, sensitive to bulk flows and halo optical depth.
Cross-ILC: Component-separation technique using internally nullified maps to isolate kSZ or lensing signals while suppressing tSZ and foregrounds.
References
- Detection of Pairwise Kinetic Sunyaev–Zel’dovich Effect with DESI Galaxy Groups and Planck in Fourier Space. The Astrophysical Journal Supplement Series (2024).
- A Cross-internal Linear Combination Approach to Probe the Secondary CMB Anisotropies: Kinematic Sunyaev–Zel’dovich Effect and CMB Lensing. The Astrophysical Journal (2023).
- Agora: Multicomponent simulation for cross-survey science. Monthly Notices of the Royal Astronomical Society (2024).
- THE KINETIC SUNYAEV–ZEL'DOVICH EFFECT AS A PROBE OF THE PHYSICS OF COSMIC REIONIZATION: THE EFFECT OF SELF-REGULATED REIONIZATION. The Astrophysical Journal (2013).
- Cross-correlating Planck tSZ with RCSLenS weak lensing: implications for cosmology and AGN feedback. Monthly Notices of the Royal Astronomical Society (2017).
- A weak gravitational lensing recalibration of the scaling relations linking the gas properties of dark haloes to their mass. Monthly Notices of the Royal Astronomical Society (2015).
- CMB/kSZ and Compton-y Maps from 2500 deg2 of SPT-SZ and Planck Survey Data. The Astrophysical Journal Supplement Series (2022).
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