B-mode polarization forecasts for GreenPol

TL;DR

GreenPol is a proposed ground-based experiment aiming to measure large-scale CMB B-mode polarization in the Northern Hemisphere, with forecasts indicating it could constrain the tensor-to-scalar ratio to r<0.02, enhancing our understanding of primordial gravitational waves.

Contribution

This paper presents the first detailed forecasts for GreenPol, a new experiment designed to improve constraints on primordial tensor modes through low-frequency CMB polarization measurements.

Findings

Projected limit of r<0.02 at 95% confidence when combined with Planck data.

GreenPol's constraints are robust against various experimental parameter variations.

The experiment could significantly advance measurements of CMB polarization in the Northern Hemisphere.

Abstract

We present tensor-to-scalar ratio forecasts for GreenPol, a hypothetical ground-based B-mode experiment aiming to survey the cleanest regions of the Northern Galactic Hemisphere at five frequencies between 10 and 44 GHz. Its primary science goal would be to measure large-scale CMB polarization fluctuations at multipoles $\ell \lesssim 500$, and thereby constrain the primordial tensor-to-scalar ratio. The observations for the suggested experiment would take place at the Summit Station (72deg N, 38deg W) on Greenland, at an altitude of 3216 m above sea level. In this paper we simulate various experimental setups, and derive limits on the tensor-to-scalar ratio after CMB component separation using a Bayesian component separation implementation called Commander. When combining the proposed experiment with Planck HFI observations for constraining polarized thermal dust emission, we find a projected limit of r<0.02 at 95 % confidence for the baseline configuration. This limit is very robust with respect to a range of important experimental parameters, including sky coverage, detector weighting, foreground priors etc. Overall, GreenPol would have the possibility to provide deep CMB polarization measurements of the Northern Galactic Hemisphere at low frequencies.