Forecasts of CMB lensing reconstruction of AliCPT-1 from the foreground cleaned polarization data

Abstract

The gravitational lensing distortion of Cosmic microwave background radiation (CMB) carries fruitful information of cosmic large-scale structure. However, CMB observations are unavoidably contaminated by emission from various extra-galactic foregrounds, which must be removed to obtain reliable measurements of the cosmological signal. In this paper, we demonstrate CMB lensing reconstruction in AliCPT-1 after foreground removal, combine the two bands of AliCPT-1 (90 and 150 GHz) with Planck HFI bands (100, 143, 217 and 353 GHz) and with the WMAP-K band (23 GHz). In order to balance contamination by instrumental noise and foreground residual bias, we adopt the Needlet Internal Linear Combination (NILC) method to clean the E-map and the constrained Internal Linear Combination (cILC) method to clean the B-map. The latter utilizes additional constraints on average frequency scaling of the dust and synchrotron to remove foregrounds at the expense of somewhat noisier maps. Assuming 4 modules observing 1 season from simulation data, the resulting effective residual noise in E- and B-map are roughly 15 μ K· arcmin and 25 μ K· arcmin, respectively. As a result, the CMB lensing reconstruction signal-to-noise ratio (SNR) from polarization data is about SNR≈4.5. This lensing reconstruction capability is comparable to that of other stage-III small aperture millimeter CMB telescopes.