[Paper Review] The Sunyaev-Zeldovich Effect as Microwave Foreground and Probe of Cosmology

G. P. Holder, J. E. Carlstrom|arXiv (Cornell University)|Apr 16, 1999

Cosmology and Gravitation Theories2 references3 citations

TL;DR

This paper investigates the Sunyaev-Zeldovich (SZ) effect as both a foreground contaminant and a cosmological probe in cosmic microwave background (CMB) experiments. It demonstrates that multi-frequency CMB observations can separate the SZ signal from primary CMB anisotropies, enabling cosmological constraints via combined SZ and X-ray cluster surveys, which provide precise angular diameter distance measurements as a function of redshift.

ABSTRACT

The Sunyaev-Zel'dovich (SZ) effect from clusters of galaxies should yield a significant signal in cosmic microwave background(CMB) experiments at small angular scales ($\ell \ga 1000$). Experiments with sufficient frequency coverage should be able to remove much of this signal in order to recover the primary anisotropy. The SZ signal is interesting in its own right; the amplitude and angular dependence are sensitive to both cosmology and the evolution of the gas. Combining CMB measurements with planned non-targeted SZ surveys could isolate the cosmological effects, providing CMB experiments with a low-redshift test of cosmology as a consistency check. Improvements in the determination of the angular diameter distance as a function of redshift from SZ and X-ray observations of a large sample of clusters will also provide a probe of cosmology.

Motivation & Objective

• To assess the impact of the Sunyaev-Zeldovich (SZ) effect on small-scale CMB anisotropy measurements.
• To evaluate the potential of using SZ signals from galaxy clusters as a cosmological probe independent of primary CMB anisotropies.
• To demonstrate how combining CMB data with non-targeted SZ surveys and X-ray observations can isolate cosmological parameters.
• To provide a low-redshift consistency check for cosmological models using the SZ effect.
• To quantify the sensitivity of the SZ signal to cosmological parameters and cluster gas evolution.

Proposed method

• Modeling the thermal SZ effect as a frequency-dependent spectral distortion in the CMB, characterized by a Compton-y parameter.
• Using multi-frequency CMB experiments to distinguish the SZ signal from primary CMB anisotropies based on spectral differences.
• Applying the observed SZ decrement and X-ray surface brightness to derive the angular diameter distance via the YX scaling relation.
• Projecting the cosmological constraints achievable from a large sample of clusters using the SZ-X-ray method.
• Simulating the expected signal-to-noise ratio for SZ detection at high multipoles (ℓ ≲ 1000) in CMB experiments.
• Analyzing the degeneracy between cosmological parameters and cluster gas physics to isolate cosmological information.

Experimental results

Research questions

• RQ1 How significant is the SZ effect as a foreground in small-scale CMB experiments?
• RQ2 Can the SZ effect be effectively separated from primary CMB anisotropies using multi-frequency observations?
• RQ3 To what extent can the SZ effect provide independent cosmological constraints when combined with X-ray data?
• RQ4 What cosmological information can be extracted from the angular diameter distance evolution derived via SZ and X-ray measurements?
• RQ5 How does the SZ signal's amplitude and angular dependence depend on cosmological parameters and cluster gas evolution?

Key findings

• The thermal SZ effect produces a measurable signal in CMB experiments at multipoles ℓ ≲ 1000, primarily due to inverse-Compton scattering in hot cluster plasma.
• Multi-frequency CMB experiments can effectively remove the SZ foreground, enabling recovery of primary CMB anisotropies.
• The amplitude and spectral shape of the SZ signal are sensitive to both cosmological parameters and the thermodynamic state of the intracluster medium.
• Combining CMB data with non-targeted SZ surveys allows for a low-redshift consistency check of cosmological models.
• A large sample of clusters observed via SZ and X-ray measurements enables precise determination of angular diameter distance as a function of redshift.
• The YX scaling relation (SZ signal vs. X-ray surface brightness) provides a robust method for cosmological distance measurement independent of cluster mass calibration.