The Square Kilometer Array as a Cosmic Microwave Background Experiment

TL;DR

This paper proposes using the Square Kilometer Array as a novel cosmic microwave background experiment to enhance measurements of primordial non-Gaussianity and low-frequency foregrounds, leveraging SKA's sensitivity at radio wavelengths.

Contribution

It introduces a new approach to utilize SKA for CMB observations, especially at low frequencies, combining it with LiteBIRD to improve constraints on primordial non-Gaussianity.

Findings

SKA can measure medium-to-large-angular-scale CMB modes at radio wavelengths.

Combining SKA with LiteBIRD improves constraints on primordial non-Gaussianity.

SKA data enhances understanding of low-frequency foregrounds.

Abstract

Contemporary cosmic microwave background (CMB) experiments typically have observing bands covering the range 20 - 800 GHz. Certain science goals, including the detection of $\mu$-type distortions to the CMB spectrum and the characterization of low-frequency foregrounds, benefit from extended low-frequency coverage, but the standard CMB detector technology is not trivially adaptable to radio wavelengths. We propose using the upcoming Square Kilometer Array (SKA) as a CMB experiment, exploiting the immense raw sensitivity of SKA, in particular in single-dish mode, to measure medium-to-large-angular-scale modes of the CMB at radio wavelengths. As a worked example, we forecast the power of SKA combined with the upcoming LiteBIRD CMB space mission to constrain primordial non-Gaussianity through measurements of the correlation between anisotropies in the CMB $\mu$-distortion, temperature, and $E$-mode polarization fields. We find that adding SKA data significantly improves the constraints on $f_\textrm{nl}$, even for spatially varying low-frequency foregrounds.