A review of interstellar polarization properties and recent measurements toward the chamaeleon I and taurus dark clouds

Gerakines, P. A.; Whittet, D. C. B.

doi:10.1016/0032-0633(95)00027-3

Cited by 2 publications

(1 citation statement)

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“…This behaviour appears to be common in the high-latitude sky and confirms previous studies. Such a decrease of the polarization fraction toward large column densities on small (∼a few 0.1 pc) scales was reported previously in ground-based measurements of polarization both in emission (Ward-Thompson et al 2000;Matthews & Wilson 2000) and extinction (e.g., Gerakines & Whittet 1995;Whittet et al 2008). This is usually interpreted as being due to a gradual loss of alignment of dust grains in dense shielded regions.…”

Section: Polarization Fraction Vs Column Densitysupporting

confidence: 76%

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

Ade¹,

Aghanim²,

Alina³

et al. 2015

A&A

315

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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.

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