Separation of anomalous and synchrotron emissions using WMAP polarization data

TL;DR

This study uses WMAP intensity and polarization data at 23 GHz to separate Galactic synchrotron and anomalous emissions, providing insights into magnetic field properties and confirming the presence of unpolarized spinning dust emission.

Contribution

It introduces a method combining WMAP data and a galactic magnetic field model to distinguish synchrotron and anomalous emissions, highlighting the role of spinning dust.

Findings

Synchrotron spectral index is approximately -3.00 with minimal spatial variation.

Polarization data supports a magnetic field with a pitch angle of -8.5 degrees.

Evidence for unpolarized spinning dust emission in the 20-60 GHz range.

Abstract

The main goals of this study is to use the information from both WMAP intensity and polarization data to do a separation of the Galactic components, with a focus on the synchrotron and anomalous emissions. Our analysis is made at 23 GHz where the signal-to-noise ratio is the highest and the estimate of the CMB map is less critical. Our estimate of the synchrotron intensity is based on an extrapolation of the Haslam 408 MHz data with a spatially varying spectral index constrained by the WMAP 23 GHz polarization data and a bi-symmetrical spiral model of the galactic magnetic field with a turbulent part following a -5/3 power law spectrum. The 23 GHz polarization data are found to be compatible with a magnetic field with a pitch angle p=-8.5 degrees and an amplitude of the turbulent part of the magnetic field 0.57 times the local value of the field, in agreement with what is found using rotation measures of pulsars and polarized extinction by dust. The synchrotron spectral index between 408 MHz and 23 GHz obtained from polarization data and our model of the magnetic field has a mean value of Beta=-3.00 with a limited spatial variation with a standard deviation of 0.06. When thermal dust, free-free and synchrotron are removed from the WMAP intensity data, the residual anomalous emission is highly correlated with thermal dust emission with a spectrum in agreement with spinning dust models. Considering a classical model of the large scale Galactic magnetic field, we show that the polarization data of WMAP are in favor of a soft synchrotron intensity highly correlated with the 408 MHz data. Furthermore the combination of the WMAP polarization and intensity data brings strong evidence for the presence of unpolarized spinning dust emission in the 20-60 GHz range.