B-mode polarization forecasts for GreenPol

¹ Institute of Theoretical Astrophysics, University of Oslo, Blindern, Oslo, Norway
e-mail: unnif@astro.uio.no
² Department of Physics, University of California, Santa Barbara, CA, USA
³ Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen, Denmark
⁴ Discovery Center, University of Copenhagen, Niels Bohr Institute, Blegdamsvej 17, Copenhagen, Denmark
⁵ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁶ School of Physics and Optoelectronics Engineering, Anhui University, 111 Jiulong Road, Hefei, Anhui 230601, PR China
⁷ Key Laboratory of Particle and Astrophysics, Institute of High Energy Physics, CAS, 19B YuQuan Road, Beijing 100049, PR China
⁸ San Diego Supercomputer Center, University of California San Diego, La Jolla, CA, USA

Received: 7 July 2023
Accepted: 24 January 2024

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 cosmic microwave background (CMB) polarization fluctuations at multipoles ℓ ≲ 500, and thereby constrain the primordial tensor-to-scalar ratio r. The observations for the suggested experiment would take place at the Summit Station (72 ° 34N, 38 ° 27W) on Greenland, at an altitude of 3216 m above sea level. For this paper we simulated various experimental setups, and derived 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 found 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, among others. Overall, GreenPol would have the possibility to provide deep CMB polarization measurements of the Northern Galactic Hemisphere at low frequencies.