Volume 654, October 2021
|Number of page(s)||25|
|Section||Interstellar and circumstellar matter|
|Published online||15 October 2021|
Local H I filaments driven by a small-scale dynamo
Unraveling the velocities and tangling of dusty magnetized structures
Argelander-Institut für Astronomie,
Auf dem Hügel 71,
2 Tartu Observatory, University of Tartu, 61602 Tõravere, Tartumaa, Estonia
Accepted: 7 August 2021
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.
Key words: ISM: clouds / ISM: structure / dust, extinction / turbulence / magnetic fields / magnetohydrodynamics (MHD)
© ESO 2021
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.