Refined modelling of the radio SZ signal: kinematic terms, relativistic temperature corrections and anisotropies in the radio background

Abstract

A significant cosmological radio background will inevitably lead to a radio Sunyaev-Zeldovich (SZ) effect. In the simplest limit, the combined signal from the scattered radio and cosmic microwave background exhibits a null at around $\nu \simeq 735$ MHz. Here, we show that kinematic and relativistic temperature corrections to this radio SZ signal are easily calculable. We treat both the cluster and observer motion, and the scattering of anisotropies in the radio background, highlighting how the spectrum of the radio SZ effect is affected in each case. Although relativistic temperature corrections only enter at the level of a few percent, our expressions allow high-precision modelling of these terms. By measuring the SZ signal around the radio null, one is in principle able to place constraints on the properties of a cosmological radio background. A combination with standard SZ measurements from large cluster samples could provide a promising avenue towards breaking degeneracies between different contributions. Stacking analyses can reduce the effect of kinematic corrections and dipolar anisotropies in the radio background, thereby providing a way to constrain the redshift dependence of the average radio background. Our qualitative discussion is meant to give an analytic understanding of the various effects and also motivate further studies with the aim to obtain quantitative forecasts of their observability. At this stage, a detection of the corrections seems rather futuristic, but the advent of large SZ and X-ray cluster samples could drastically improve our ability to disentangle various effects.

Accepted by MNRAS

References in corpus (5)

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Cited by in corpus (9)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• The Second Radio Synchrotron Background Workshop: Conference Summary and Report
• A multi-simulation study of relativistic SZ temperature scalings in galaxy clusters and groups
• Can accreting primordial black holes explain the excess radio background?
• A closer look at dark photon explanations of the excess radio background
• Inverse-Compton Scattering of the Cosmic Infrared Background
• Importance of intracluster scattering and relativistic corrections from tSZ effect with Cosmic Infrared Background
• Increase in the Brightness of the Cosmic Radio Background toward Galaxy Clusters
• The non-thermal secondary CMB anisotropies from a cosmic distribution of radio galaxy lobes