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标题：Link between E– B polarization modes and gas column density from interstellar dust emission ★
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作者：Andrea Bracco ; Tuhin Ghosh ; François Boulanger 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：632
页码：1-10
DOI：10.1051/0004-6361/201935951
语种：English
出版社：EDP Sciences
摘要：Context.The analysis of thePlanckpolarizationEandBmode power spectra of interstellar dust emission at 353 GHz recently raised new questions concerning the impact of Galactic foregrounds on the detection of the polarization of the cosmic microwave background (CMB) and on the physical properties of the interstellar medium (ISM). In the diffuse ISM at high latitude a clearE–Basymmetry is observed that has twice as much power inEmodes as inBmodes; there is also a positive correlation between the total power,T, and bothEandBmodes, which is currently interpreted in terms of the link between the structure of interstellar matter and that of the Galactic magnetic field.Aims.In this paper we aim to extend thePlanckanalysis of the high latitude sky to low Galactic latitudes, investigating the correlation between theT–E–Bauto- and cross-correlation power spectra with the gas column density from the diffuse ISM to molecular clouds.Methods.We divided the sky between Galactic latitudes |b| > 5° and |b| < 60° in 552 circular patches, with an area of ~400°2, and we studied the cross-correlations between theT–E–Bpower spectra and the column density of each patch using the latest release of thePlanckpolarization data.Results.We find that theB-to-Epower ratio (DlBB/DlEE) and theTEcorrelation ratio (rTE) depend on column density. While the former increases going from the diffuse ISM to molecular clouds in the Gould Belt, the latter decreases. This systematic variation must be related to actual changes in ISM properties. The data show significant scatter about this mean trend. The variations ofDlBB/DlEEandrTEare observed to be anticorrelated for all column densities. In the diffuse ISM, the variance of these two ratios is consistent with a stochastic non-Gaussian model in which the values ofDlBB/DlEEandrTEare fixed. We finally discuss the dependences ofTBandEBwith column density, which are however hampered by instrumental noise.Conclusions.For the first time, this work shows significant variations of theT–E–Bpower spectra of dust polarized emission across a large portion of the Galaxy. Their dependence on multipole and gas column density is key for accurate forecasts of next generation CMB experiments and for constraining present models of ISM physics (i.e., dust properties and interstellar turbulence), which are considered responsible for the observedT–E–Bsignals.
关键词：Key wordsendust, extinctionpolarizationISM: magnetic fieldscosmic background radiationlocal insterstellar matterISM: clouds