Galactic interstellar filaments as probed by LOFAR and Planck

TL;DR

This study finds a surprising correlation between filamentary structures observed in radio polarization by LOFAR and the magnetic field orientation from Planck dust maps, suggesting a common physical origin in the interstellar medium.

Contribution

It reveals an unexpected correlation between LOFAR polarization filaments and Planck magnetic field orientation, indicating a new link in understanding interstellar magnetic structures.

Findings

LOFAR detects filamentary polarization structures over 4 degrees.

Planck maps show magnetic field orientation via dust polarization.

A clear correlation exists between LOFAR filaments and magnetic field orientation.

Abstract

Recent Low Frequency Array (LOFAR) observations at 115-175 MHz of a field at medium Galactic latitudes (centered at the bright quasar 3C196) have shown striking filamentary structures in polarization that extend over more than 4 degrees across the sky. In addition, the Planck satellite has released full sky maps of the dust emission in polarization at 353GHz. The LOFAR data resolve Faraday structures along the line of sight, whereas the Planck dust polarization maps probe the orientation of the sky projected magnetic field component. Hence, no apparent correlation between the two is expected. Here we report a surprising, yet clear, correlation between the filamentary structures, detected with LOFAR, and the magnetic field orientation, probed by the Planck satellite. This finding points to a common, yet unclear, physical origin of the two measurements in this specific area in the sky. A number of follow-up multi- frequency studies are proposed to shed light on this unexpected finding.