# Planck intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization

Abstract : Planck has mapped the intensity and polarization of the sky at microwave frequencies with unprecedented sensitivity. We make use of the Planck 353 GHz I, Q, and U Stokes maps as dust templates, and cross-correlate them with the Planck and WMAP data at 12 frequencies from 23 to 353 GHz, over circular patches with 10 degree radius. The cross-correlation analysis is performed for both intensity and polarization data in a consistent manner. We use a mask that focuses our analysis on the diffuse interstellar medium at intermediate Galactic latitudes. We determine the spectral indices of dust emission in intensity and polarization between 100 and 353 GHz, for each sky-patch. The mean values, $1.63\pm0.03$ for polarization and $1.52\pm0.02$ for intensity, for a mean dust temperature of 18.7 K, are close, but significantly different. We determine the mean spectral energy distribution (SED) of the microwave emission, correlated with the 353 GHz dust templates, by averaging the results of the correlation over all sky-patches. We find that the mean SED increases for decreasing frequencies at $\nu < 60$ GHz, for both intensity and polarization. The rise of the polarization SED towards low frequencies may be accounted for by a synchrotron component correlated with dust, with no need for any polarization of the anomalous microwave emission. We use a spectral model to separate the synchrotron and dust polarization and to characterize the spectral dependence of the dust polarization fraction. The polarization fraction ($p$) of the dust emission decreases by $(34\pm10)$ % from 353 to 70 GHz. The decrease of $p$ could indicate differences in polarization efficiency among components of interstellar dust (e.g., carbon versus silicate grains), or, alternatively, it could be a signature of magnetic dipole emission from ferromagnetic inclusions within interstellar grains.
Keywords :
Document type :
Journal articles
Domain :

http://hal.in2p3.fr/in2p3-01000147
Contributor : Sabine Starita Connect in order to contact the contributor
Submitted on : Wednesday, June 4, 2014 - 11:21:36 AM
Last modification on : Tuesday, November 23, 2021 - 9:48:08 AM

### Citation

P. A. R. Ade, M. I. R. Alves, G. Aniano, C. Armitage-Caplan, M. Arnaud, et al.. Planck intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization. Astronomy and Astrophysics - A&A, EDP Sciences, 2015, 576, pp.A107. ⟨10.1051/0004-6361/201424088⟩. ⟨in2p3-01000147⟩

### Metrics

Les métriques sont temporairement indisponibles