Forecast on the delensing of AliCPT-1 project
Abstract
The gravitational scattering from foreground large-scale structures to the primary cosmic microwave background (CMB) photons distorts the linear polarization pattern, converting E-mode into B-mode polarization. The resulting signal is referred to as Lensing-B mode, which strongly contaminates measurements of the primordial B-mode produced by primordial gravitational waves. To measure the primordial B-mode with a high degree of precision, we must subtract the Lensing-B mode at the map level. This operation is called delensing. The Ali CMB polarization telescope 1st-phase project (AliCPT-1) is the first ground-based cosmological millimeter survey in the northern hemisphere. This article forecasts AliCPT-1's lensing reconstruction and delensing capacity based on simulated data over five seasons. A signal-to-noise ratio of 13.4 can be achieved for lensing reconstruction. Two methods were employed for delensing: the “internal” and “external” methods. The former relies solely on CMB data, while the latter requires cosmic infrared background data. Furthermore, we find that the delensing efficiency of the internal method is lower than that of the external method. The maximum delensing efficiency for the internal method peaks at the spherical harmonic mode ell=50 with an amplitude of 10%, whereas that of the external method peaks at ell∼eq200 with an amplitude of 20%. The external delensing method could improve the measured value of the tensor-to-scalar ratio from r≤0.03 to r≤0.02.
