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We explore the potential use of the Radio Continuum (RC) survey conducted by the Square Kilometre Array (SKA) to remove (delens) the lensing-induced B-mode polarization and thus enhance future cosmic microwave background (CMB) searches for inflationary gravitational waves. Measurements of large-scale B-modes of the CMB are considered to be the best method for probing gravitational waves from the cosmic inflation. Future CMB experiments will, however, suffer from contamination by nonprimordial B modes, one source of which is the lensing B modes. Delensing, therefore, will be required for further improvement of the detection sensitivity for gravitational waves. Analyzing the use of the two-dimensional map of galaxy distribution provided by the SKA RC survey as a lensing mass tracer, we find that joint delensing using near-future CMB experiments and the SKA phase 1 will improve the constraints on the tensor-to-scalar ratio by more than a factor of ∼2 compared to those without the delensing analysis. Compared to the use of CMB data alone, the inclusion of the SKA phase 1 data will increase the significance of the constraints on the tensor-to-scalar ratio by a factor 1.2–1.6. For LiteBIRD combined with a ground-based experiment such as Simons Array and Advanced ACT, the constraint on the tensor-to-scalar ratio when adding SKA phase 2 data is improved by a factor of 2.3–2.7, whereas delensing with CMB data alone improves the constraints by only a factor 1.3–1.7. We conclude that the use of SKA data is a promising method for delensing upcoming CMB experiments such as LiteBIRD.
Research papers (academic journals)
