A Survey of the Polarized Emission from the Galactic Plane at 1420 MHz with Arcminute Angular Resolution

TL;DR

This extensive 1.4 GHz polarization survey of the Galactic plane combines aperture synthesis and single-dish data to reveal magnetic field structures and Faraday effects across multiple scales, providing new insights into the interstellar medium.

Contribution

It is the first large-scale polarization survey that combines data from multiple telescopes with arcminute resolution, enhancing understanding of Galactic magnetic fields.

Findings

Polarized emission is dominated by Faraday rotation effects.

Diffuse polarized sky differs significantly from total-intensity sky.

Depolarization occurs due to line-of-sight effects and ionized regions.

Abstract

Context: Observations of polarized emission are a significant source of information on the magnetic field that pervades the Interstellar Medium of the Galaxy. Despite the acknowledged importance of the magnetic field in interstellar processes, our knowledge of field configurations on all scales is seriously limited. Aims: This paper describes an extensive survey of polarized Galactic emission at 1.4 GHz that provides data with arcminute resolution and complete coverage of all structures from the broadest angular scales to the resolution limit, giving information on the magneto-ionic medium over a wide range of interstellar environments. Methods: Data from the DRAO Synthesis Telescope, the Effelsberg 100-m Telescope, and the DRAO 26-m Telescope have been combined. Angular resolution is ~1' and the survey extends from l = 66 deg to l = 175 deg over a range -3 deg < b < 5 deg along the northern Galactic plane, with a high-latitude extension from l = 101 deg to l = 116 deg up to b = 17.5 deg. This is the first extensive polarization survey to present aperture-synthesis data combined with data from single antennas, and the techniques developed to achieve this combination are described. Results: The appearance of the extended polarized emission at 1.4 GHz is dominated by Faraday rotation along the propagation path, and the diffuse polarized sky bears little resemblance to the total-intensity sky. There is extensive depolarization, arising from vector averaging on long lines of sight, from HII regions, and from diffuse ionized gas seen in H-alpha images. Preliminary interpretation is presented of selected polarization features on scales from parsecs (the planetary nebula Sh 2-216) to hundreds of parsecs (a supperbubble GSH 166-01-17) to kiloparsecs (polarized emission in the direction of Cygnus X).