Square Kilometer Array as a cosmic microwave background experiment

Contemporary cosmic microwave background (CMB) experiments typically have observing bands covering the range 20--800 GHz. Certain science goals, including the detection of $\ensuremath{\mu}$-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 $\ensuremath{\mu}$-distortion, temperature, and $E$-mode polarization fields. We find that adding SKA data significantly improves the constraints on ${f}_{\mathrm{NL}}$, even for spatially varying low-frequency foregrounds.