A template of atmospheric molecular oxygen circularly polarized emission for CMB experiments

TL;DR

This paper models the circularly polarized emission of atmospheric molecular oxygen caused by the Zeeman effect, providing templates for different CMB observation sites to aid in signal calibration and noise mitigation.

Contribution

It introduces a detailed template of atmospheric oxygen polarization for CMB sites, accounting for magnetic field and atmospheric variations, which was not previously available.

Findings

Typical V Stokes parameter level of 50-300 μK at 90 GHz at zenith

Dome C has the lowest polarization gradient among sites

Template robustness tested against magnetic and atmospheric variability

Abstract

We compute the polarized signal from atmospheric molecular oxygen due to Zeeman effect in the Earth magnetic field for various sites suitable for CMB measurements such as South Pole, Dome C (Antarctica) and Atacama desert (Chile). We present maps of this signal for those sites and show their typical elevation and azimuth dependencies. We find a typical circularly polarized signal (V Stokes parameter) level of 50 - 300 \mu K at 90 GHz when looking at the zenith; Atacama site shows the lowest emission while Dome C site presents the lowest gradient in polarized brightness temperature (0.3 \mu K/deg at 90 GHz). The accuracy and robustness of the template are tested with respect to actual knowledge of the Earth magnetic field, its variability and atmospheric parameters.