Cleaning up the CMB: Using S-PASS and WMAP data to investigate the synchrotron foreground.
CMB detectors measure all incoming radiation of a certain frequency. So our data consists of both the pure CMB signal and other sources we call foregrounds. Foregrounds are typically radiation from our own galaxy, "polluting" the signal. The dominating polarized foreground at low frequency is the synchrotron foreground. A major job in CMB analysis is therefore to constrain the foregrounds themselves so that we can remove them from the data with the required accuracy.
In this talk I will present the recently released S-PASS data and the 9yr WMAP data, and with a simple but robust scatter plot method estimate the spectral index of the polarized synchrotron emission. The analysis is done in regions of the sky to get the spatial variation. One key aspect of the analysis is to Faraday correct the low frequency data. The Faraday effect causes rotation of the plane of polarization of an electromagnetic wave in the presence of a magnetic field.
The results in this talk are from the recent paper https://arxiv.org/abs/1909.05923, Constraints on the spectral index of polarized synchrotron emission from WMAP and Faraday-corrected S-PASS data.