Associating LOFAR Galactic Faraday structures with the warm neutral medium

Faraday tomography observations with the Low Frequency Array (LOFAR) have unveiled a remarkable network of structures in polarized synchrotron emission at high Galactic latitudes. The observed correlation between LOFAR structures, dust polarization, and H I emission suggests a connection to the neut...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2024-07, Vol.687, p.A102
Main Authors: Boulanger, F., Gry, C., Jenkins, E. B., Bracco, A., Erceg, A., Jelić, V., Turić, L.
Format: Article
Language:English
Subjects:
Absorption spectra
Astrophysics
Bulk density
Cosmic dust
Emission spectra
Interstellar matter
LOFAR
Northern sky
Physics
Polarization
Sky surveys (astronomy)
Spectrum analysis
Stars
Stellar magnetic fields
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Summary:Faraday tomography observations with the Low Frequency Array (LOFAR) have unveiled a remarkable network of structures in polarized synchrotron emission at high Galactic latitudes. The observed correlation between LOFAR structures, dust polarization, and H I emission suggests a connection to the neutral interstellar medium (ISM). We investigated this relationship by estimating the rotation measure (RM) of the warm neutral (partially ionized) medium (WNM) in the local ISM. Our work combines UV spectroscopy from FUSE and dust polarization observations from Planck with LOFAR data. We derived electron column densities from UV absorption spectra toward nine background stars, within the field of published data from the LOFAR two-meter sky survey. The associated RMs were estimated using a local magnetic field model fitted to the dust polarization data of Planck. A comparison with Faraday spectra at the position of the stars suggests that LOFAR structures delineate a slab of magnetized WNM and synchrotron emission, located ahead of the bulk of the warm ionized medium. This conclusion establishes an astrophysical framework for exploring the link between Faraday structures and the dynamics of the magnetized multiphase ISM. It will be possible to test it on a larger sample of stars when maps from the full northern sky survey of LOFAR become available.
ISSN:0004-6361
1432-0746
1432-0756
DOI:10.1051/0004-6361/202348953