Planckintermediate results. XIX. An overview of the polarized thermal emission from Galactic dust

Abstract

This paper presents an overview of the polarized sky as seen by Planck HFI at 353 GHz, which is the most sensitive Planck channel for dust polarization. We construct and analyse maps of dust polarization fraction and polarization angle at 1• resolution, taking into account noise bias and possible systematic effects. The sensitivity of the Planck HFI polarization measurements allows for the first time a mapping of Galactic dust polarized emission on large scales, including low column density regions. We find that the maximum observed dust polarization fraction is high (p max = 19.8%), in particular in some regions of moderate hydrogen column density (N H < 2 × 10 21 cm −2 ). The polarization fraction displays a large scatter at N H below a few 10 21 cm −2 . There is a general decrease in the dust polarization fraction with increasing column density above N H 1 × 10 21 cm −2 and in particular a sharp drop above N H 1.5 × 10 22 cm −2 . We characterize the spatial structure of the polarization angle using the angle dispersion function. We find that the polarization angle is ordered over extended areas of several square degrees, separated by filamentary structures of high angle dispersion function. These appear as interfaces where the sky projection of the magnetic field changes abruptly without variations in the column density. The polarization fraction is found to be anti-correlated with the dispersion of polarization angles. These results suggest that, at the resolution of 1• , depolarization is due mainly to fluctuations in the magnetic field orientation along the line of sight, rather than to the loss of grain alignment in shielded regions. We also compare the polarization of thermal dust emission with that of synchrotron measured with Planck, low-frequency radio data, and Faraday rotation measurements toward extragalactic sources. These components bear resemblance along the Galactic plane and in some regions such as the Fan and North Polar Spur regions. The poor match observed in other regions shows, however, that dust, cosmic-ray electrons, and thermal electrons generally sample different parts of the line of sight.

Improved Constraints on Cosmology and Foregrounds from BICEP2 and Keck Array Cosmic Microwave Background Data with Inclusion of 95 GHz Band

“…Additional measurements at 150 GHz taken by the Keck Array during 2012 and 2013 confirmed this excess [11]. However, new data from the Planck space mission provided evidence that emission from galactic dust grains could be more polarized at high galactic latitudes than anticipated [12,13], a possibility emphasized in Refs. [14,15].…”

The powers of monodromy

“…In particular, in the context of inflation [2][3][4][5], an observation of a tensor-to-scalar ratio r 10 −2 implies an unprecedented connection between empirical observations and quantum gravity, for two reasons: it provides a measurement of the quantum mechanical variance of the tensor modes of the metric [6][7][8][9][10][11][12][13], and it indicates a super-Planckian field excursion [14,15]. An impressive variety of observational efforts are approaching the sensitivity required to detect r in this range [16], with a recent report of a detection of B-mode polarization [17,18] that may contain a signal of primordial origin corresponding to inflationary tensor modes [19,20], depending on the outcome of important foreground measurements generalizing [21,22].…”

Inflationary Cosmology in Modified Gravity Theories

“…There have been proposed several discussions on the method to obtain this result regarding the subtraction of the foreground data, e.g., References [58][59][60][61][62]. A study to support the BICEP2 results has also been reported in Reference [63].…”