Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
Metadatos
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EDP Sciences SA
Materia
ISM: general Dust Extinction ISM: magnetic fields ISM: clouds Submillimeter: ISM
Fecha
2015-04-13Referencia bibliográfica
Ade, P. A. R., Aghanim, N., Alina, D., Alves, M. I. R., Armitage-Caplan, C., Arnaud, M., ... & Baccigalupi, C. (2015). Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust. Astronomy & Astrophysics, 576, A104. [DOI: 10.1051/0004-6361/201424082]
Patrocinador
European Space Agency; Centre National D'etudes Spatiales; CNRS/INSU-IN2P3-INP (France); Agenzia Spaziale Italiana (ASI); Consiglio Nazionale delle Ricerche (CNR); Istituto Nazionale Astrofisica (INAF); National Aeronautics & Space Administration (NASA); United States Department of Energy (DOE); Science & Technology Facilities Council (STFC); UKSA (UK); Consejo Superior de Investigaciones Cientificas (CSIC); MICINN, J.A. (Spain); RES (Spain); Finnish Funding Agency for Technology & Innovation (TEKES); AoF (Finland); CSC (Finland); Helmholtz Association German Aerospace Centre (DLR); Max Planck Society; CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); Science Foundation Ireland; Portuguese Foundation for Science and Technology; European Union (EU); European Research Council (ERC) 267934; University of Sao Paulo, Brazil USP 2007.1.433.14.2 COFECUB Uc Te 114/08; COFECUB, France USP 2007.1.433.14.2 COFECUB Uc Te 114/08; Science & Technology Facilities Council (STFC) ST/M001334/1 ST/N000056/1 ST/K000985/1 ST/K002821/1 ST/K004131/1 ST/F010885/1 ST/K00106X/1 ST/L000768/1 ST/K001051/1; UK Space Agency ST/M007685/1 ST/N001206/1 ST/H001212/1 ST/K003674/1 ST/N001095/1Resumen
This paper presents an overview of the polarized sky as seen by Planck HFI at 353GHz, 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 (pmax = 19.8%), in particular in some regions of moderate hydrogen column density (NH < 2 × 1021 cm−2). The polarization fraction displays
a large scatter at NH below a few 1021 cm−2. There is a general decrease in the dust polarization fraction with increasing column density above
NH 1×1021 cm−2 and in particular a sharp drop above NH 1.5×1022 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.