Physical processes in the ISM

Frequency Dependence of Dust Polarization from Planck

Not scheduled

5h

MPE

Poster

Speaker

Tuhin Ghosh (Institut d'Astrophysique Spatiale)

Description

Planck has mapped the polarization of the sky emission at microwave frequencies with unprecedented sensitivity. We use the data to characterise the frequency dependence of Galactic polarization. We make use of the cross-correlation analysis which is an established method to characterise the spectral properties of Galactic emission at microwave frequencies. We take the Planck 353 GHz HFI frequency intensity and polarization maps as representative dust templates, and cross-correlate them with other HFI frequency maps over circular patches with 10 degree radius at intermediate Galactic latitudes. The cross-correlation analysis is performed on both intensity and polarization anisotropy measurements of Planck in a consistent manner. In the first part of the data analysis, we determine the spectrum of the polarized dust emission between 100 and 353 GHz. We find that the spectral indices of temperature and polarized dust emission differs by 0.1 at microwave frequencies. The polarization degree is observed to be constant within an uncertainty of 10 % from 100 to 353 GHz. In the second part, we extend the cross-correlation analysis to WMAP and LFI frequencies. We find a turnover in the amplitude of the dust correlated polarization spectrum towards frequencies smaller than about 60 GHz, very much like what has been found earlier on intensity data. We show that the low frequency polarization correlated with the 353 GHz template may be accounted for by polarized synchrotron emission with no need for any AME polarization. These observational results are key to the separation of Galactic and CMB polarization. They also constrain existing models of the microwave emission of dust.