A template of atmospheric O2 circularly polarized emission for cosmic microwave background experiments

We compute the circularly polarized signal from atmospheric molecular oxygen. The polarization of O2 rotational lines is caused by the Zeeman effect in the Earth’s magnetic field. We evaluate the circularly polarized emission for various sites suitable for cosmic microwave background (CMB) measurements: the South Pole and Dome C (Antarctica), Atacama (Chile) and Testa Grigia (Italy). We present and discuss an analysis of the polarized signal within the framework of future CMB polarization experiments. We find a typical circularly polarized signal (V Stokes parameter) of 50–300 μK at 90 GHz looking at the zenith. Among the sites, Atacama shows a lower polarized signal at the zenith. We present maps of this signal for the various sites and we show typical elevation and azimuth scans. We find that Dome C presents the lowest gradient in polarized temperature: 0.3 μK/deg at 90 GHz. We also study the frequency bands of observation: around ν=100 GHz and ν=160 GHz, we find the best conditions because the polarized signal vanishes. Finally, we evaluate the accuracy of the templates and the signal variability in relation to our knowledge of and the variability of the Earth’s magnetic field and atmospheric parameters.

We compute the circularly polarized signal from atmospheric molecular oxygen. The polarization of O2 rotational lines is caused by the Zeeman effect in the Earth's magnetic field. We evaluate the circularly polarized emission for various sites suitable for cosmic microwave background (CMB) measurements: the South Pole and Dome C (Antarctica), Atacama (Chile) and Testa Grigia (Italy). We present and discuss an analysis of the polarized signal within the framework of future CMB polarization experiments. We find a typical circularly polarized signal (V Stokes parameter) of ∼50-300μK at 90GHz looking at the zenith. Among the sites, Atacama shows a lower polarized signal at the zenith. We present maps of this signal for the various sites and we show typical elevation and azimuth scans. We find that Dome C presents the lowest gradient in polarized temperature: ∼0.3μK deg-1 at 90GHz. We also study the frequency bands of observation: around ν≃ 100GHz and ν≃ 160GHz, we find the best conditions because the polarized signal vanishes. Finally, we evaluate the accuracy of the templates and the signal variability in relation to our knowledge of and the variability of the Earth's magnetic field and atmospheric parameters. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.