New continuum and polarization observations of the Cygnus Loop with FAST

TL;DR

This paper presents high-resolution, sensitive continuum and polarization observations of the Cygnus Loop supernova remnant using FAST, including the first application of RM synthesis to this object, enhancing understanding of its magnetic structure.

Contribution

The study provides the first application of RM synthesis to the Cygnus Loop, offering detailed polarization and RM maps with high sensitivity and resolution, validating calibration procedures.

Findings

High-resolution polarization maps of the Cygnus Loop

First RM synthesis application to this SNR

Accurate RMs for eight extragalactic sources

Abstract

We report on the continuum and polarization observations of the Cygnus Loop supernova remnant (SNR) conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). FAST observations provide high angular resolution and high sensitivity images of the SNR, which will help to disentangle its nature. We obtained Stokes I, Q and U maps over the frequency range of 1.03 - 1.46 GHz split into channels of 7.63 kHz. The original angular resolution is in the range of ~3 arcmin - ~3.8 arcmin, and we combined all the data at a common resolution of 4 arcmin. The temperature scale of the total intensity and the spectral index from the in-band temperature-temperature plot are consistent with previous observations, which validates the data calibration and map-making procedures. The rms sensitivity for the band-averaged total-intensity map is about 20 mK in brightness temperature, which is at the level of confusion limit. For the first time, we apply rotation measure (RM) synthesis to the Cygnus Loop to obtain the polarization intensity and RM maps. The rms sensitivity for polarization is about 5 mK, far below the total-intensity confusion limit. We also obtained RMs of eight extra-galactic sources, and demonstrate that the wide-band frequency coverage helps to overcome the ambiguity of RM determinations.