Forecast of cross-correlation of Chinese Survey Space Telescope cosmic shear tomography with Ali CMB Polarization Telescope cosmic microwave background lensing

Abstract

ABSTRACT We present a forecast study on the cross-correlation between cosmic shear tomography from the Chinese Survey Space Telescope (CSST) and cosmic microwave background (CMB) lensing from Ali CMB Polarization Telescope (AliCPT-1) in Tibet. The correlated galaxy and CMB lensing signals were generated from Gaussian realizations based on inputted auto and cross-spectra. To account for the error budget, we considered the CMB lensing reconstruction noise based on the AliCPT-1 lensing reconstruction pipeline; shape noise of the galaxy lensing measurement; CSST photo-z error; photo-z bias; intrinsic alignment (IA) effect; and multiplicative bias. The AliCPT-1 CMB lensing mock data were generated according to two experimental stages, namely the ‘4 modules*yr’ and ‘48 modules*yr’ cases. We estimate the cross-spectra in four tomographic bins according to the CSST photo-z distribution in the range of z ∈ [0, 4). After reconstructing the pseudo-cross-spectra from the realizations, we calculate the signal-to-noise ratio (SNR). By combining the four photo-z bins, the total cross-correlation SNR ≈ 15 (AliCPT-1 ‘4 modules*yr’) and SNR ≈ 22 (AliCPT-1 ‘48 modules*yr’). Finally, we study the cosmological application of this cross-correlation signal. Excluding IA in the template fitting would lead to roughly a 0.6σ increment in σ8 due to the negative IA contribution to the galaxy lensing data. For AliCPT-1 first and second stages, the cross-correlation of CSST cosmic shear with CMB lensing gives errors on the clustering amplitude $\sigma _{\sigma _8}=^{+0.043}_{-0.038}$ or $\sigma _{S_8}=\pm 0.031$ and $\sigma _{\sigma _8}=^{+0.030}_{-0.027}$ or $\sigma _{S_8}=\pm 0.018$, respectively.