Turbulent Structure In Supernova Remnants G46.8-0.3 And G39.2-0.3 From THOR Polarimetry

TL;DR

This study analyzes the turbulent magnetic structures in supernova remnants G46.8-0.3 and G39.2-0.3 using polarization and Faraday rotation data from the THOR survey, revealing small-scale fluctuations and their origins.

Contribution

It provides the first detailed measurement of Faraday depth fluctuations at sub-arcminute scales in these SNRs, linking turbulence to the remnants' internal magnetic structures.

Findings

Median Faraday dispersion sigma_phi ~16-18 rad/m^2 in the SNRs.

Evidence of small-scale turbulence with sigma_phi >~ 30 rad/m^2 in localized regions.

Faraday fluctuations mainly originate within the SNRs, not the foreground ISM.

Abstract

We present the continued analysis of polarization and Faraday rotation for the supernova remnants (SNRs) G46.8-0.3 and G39.2-0.3 in L-band (1-2 GHz) radio continuum in The HI/OH/Recombination line (THOR) survey. In this work, we present our investigation of Faraday depth fluctuations from angular scales comparable to the size of the SNRs down to scales less than our 16" beam (<~0.7 pc) from Faraday dispersion (sigma_phi). From THOR, we find median sigma_phi of 15.9 +/- 3.2 rad m^-2 for G46.8-0.3 and 17.6 +/- 1.6 rad m^-2 for G39.2-0.3. When comparing to polarization at 6cm, we find evidence for sigma_phi >~ 30 rad m^-2 in localized regions where we detect no polarization in THOR. We combine Faraday depth dispersion with the rotation measure (RM) structure function (SF) and find evidence for a break in the SF on scales less than the THOR beam. We estimate the RM SF of the foreground interstellar medium (ISM) using the SF of extra-Galactic radio sources (EGRS) and pulsars to find that the RM fluctuations we measure originate within the SNRs for all but the largest angular scales.