2023ApJ...952...94X

We have obtained the polarization data cube of the supernova remnant (SNR) VRO 42.05.01 at 1240 MHz using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). Three-dimensional Faraday synthesis is applied to the FAST data to derive the Faraday depth spectrum. The peak Faraday depth map shows a large area of enhanced foreground rotation measure (RM) of ∼60 rad m^–2 extending along the remnant's “wing” section, which coincides with a large-scale H I shell at -20 km s^–1. The two depolarization patches within the “wing” region with RMs of 97 rad m^–2 and 55 rad m^–2 coincide with two H I structures in the H I shell. Faraday screen model fitting on the Canadian Galactic Plane Survey 1420 MHz full-scale polarization data reveals a distance of (0.7-0.8)d_SNR in front of the SNR with enhanced regular magnetic field there. The highly piled-up magnetic field indicates that the H I shell at -20 km s^–1 could originate from an old evolved SNR.