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À propos de : Local H  I filaments driven by a small-scale dynamo        

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  • Unraveling the velocities and tangling of dusty magnetized structures
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  • Local H  I filaments driven by a small-scale dynamo
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Abstract
  • Context. H  I filaments are closely related to dusty magnetized structures that are observable in the far infrared (FIR). Recently it was proposed that the coherence of oriented H  I structures in velocity traces the line of sight magnetic field tangling. Aims. We study the velocity-dependent coherence between FIR emission at 857 GHz and H  I on angular scales of 18′. Methods. We use HI4PI H  I data and Planck FIR data and apply the Hessian operator to extract filaments. For coherence, we require that local orientation angles θ in the FIR at 857 GHz along the filaments be correlated with the H  I. Results. We find some correlation for H  I column densities at | vLSR| < 50 km s −1, but a tight agreement between FIR and H  I orientation angles θ exists only in narrow velocity intervals of 1 km s −1. Accordingly, we assign velocities to FIR filaments. Along the line of sight these H  I structures show a high degree of the local alignment with θ, as well as in velocity space. Interpreting these aligned structures in analogy to the polarization of dust emission defines an H  I polarization. We observe polarization fractions of up to 80%, with averages of 30%. Orientation angles θ along the filaments, projected perpendicular to the line of sight, are fluctuating systematically and allow a characteristic distribution of filament curvatures to be determined. Conclusions. Local H  I and FIR filaments identified by the Hessian analysis are coherent structures with well-defined radial velocities. H  I structures are also organized along the line of sight with a high degree of coherence. The observed bending of these structures in the plane of the sky is consistent with models for magnetic field curvatures induced by a Galactic small-scale turbulent dynamo.
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  • aa40274-21
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  • © ESO 2021
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  • ESO
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