Performance forecasts for the primordial gravitational wave detection pipelines for AliCPT-1

Abstract

AliCPT is the first Chinese cosmic microwave background (CMB) experiment which will make the most precise measurements of the CMB polarization in the northern hemisphere. The key science goal for AliCPT is the detection of primordial gravitational waves (PGWs). It is well known that an epoch of cosmic inflation, in the very early universe, can produce PGWs, which leave an imprint on the CMB in form of odd parity B-mode polarization. In this work, we study the performance of the component separation and parameter estimation pipelines in context of constraining the value of the tensor-to-scalar ratio. Based on the simulated data for one observation season, we compare five different pipelines with different working principles. Three pipelines perform component separation at map or spectra level before estimating r from the cleaned spectra, while the other two pipelines performs a global fit for both foreground parameters and r. We also test different methods to account for the effects of time stream filtering systematics. This work shows that our pipelines provide consistent and robust constraints on the tensor-to-scalar ratio and a consistent sensitivity σ(r) ∼ 0.02. This showcases the potential of precise B-mode polarization measurement with AliCPT-1. AliCPT will provide a powerful opportunity to detect PGWs, which is complementary with various ground-based CMB experiments in the southern hemisphere.

Removal of point source leakage from time-order data filtering

“…This is true according to Ghosh et al [16], which shows the small scale structures are almost unaffected by the TOD filtering. II The point source mask is big enough to include the majority of the point source.…”

“…Especially, all available CMB experiments in the next 5-10 years are ground-based, which are ineluctably contaminated by the atmosphere and ground emissions. In order to produce clean sky maps, filtering of modes (including polynominal filtering) in the time ordered data (TOD) is used in many CMB experiments to avoid/alleviate these contaminations, and has become a standard procedure in data processing pipeline of ground-based CMB experiments, such as in the BICEP2/Keck experiment [8], the Simons Observatory [14], and AliCPT [16].…”

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

“…We re-observe the coadded sky map consisting of signal and noise in each band, using the same number of detectors as AliCPT-1's single band. The detailed pipeline is presented in [12].…”

Future Prospects on Constraining Neutrino Cosmology with the Ali CMB Polarization Telescope

“…For the foreground removal procedure, AliCPT will initially use sky maps from Planck HFI four bands and WMAP K band to increase frequency coverage and improve foreground removal efficiency. Component separation methods will be used in the pipelines of AliCPT as described in Santos et al (2019), Remazeilles et al (2021), andGhosh et al (2022). In the future, AliCPT will explore the possibility of building more channels for corresponding observations.…”