The Crab Nebula as a Calibrator for wide-beam Cosmic Microwave Background polarization surveys

TL;DR

This paper investigates how polarized diffuse emission affects the calibration of wide-beam CMB polarization experiments using the Crab Nebula, emphasizing the need for precise, high-resolution reference maps to prevent bias in B-mode detection.

Contribution

It demonstrates the importance of high-resolution, precise reference maps for calibrating wide-beam CMB polarization experiments using the Crab Nebula.

Findings

Diffuse polarized emission can bias calibration if not properly accounted for.

High angular resolution and precision are required for reference maps in B-mode experiments.

Proper calibration is crucial for accurate detection of primordial gravitational waves.

Abstract

We analyze the effect of polarized diffuse emission in the calibration of wide-beam mm-wave polarimeters, when using the Crab Nebula as a reference source for both polarized brightness and polarization angle. We show that, for CMB polarization experiments aiming at detecting B-mode in a scenario with a tensor to scalar ratio $r \sim 0.001$, wide (a few degrees in diameter), precise ($\sigma_Q$ , $\sigma_U$ $\sim$ 20 $\mu$$K_{CMB}$ arcmin), high angular resolution ($< \mathrm{FWHM}$) reference maps are needed to properly take into account the effects of diffuse polarized emission and avoid significant bias in the calibration.