Five Mature Supernova Remnants in the Large Magellanic Cloud

Abstract

Radio observations of the extended supernova remnants (SNRs) N23:SNR, N120:SNR, 0525-660, N49, and N44:shell 3 in the Large Magellanic Cloud show a variety of structures and little difference from shell SNRs in the Milky Way. N23:SNR and N120:SNR have very regular outlines, but the shells are much brighter on the sides toward the most prominent parts of their associated H II region complexes, probably reflecting density gradients in the surroundings. N23:SNR has a mixed magnetic field orientation and a mean magnetic field strength of 15 μG. Its magnetic energy is about 4 times less than the relativistic electron energy. SNR 0525-660 appears to be isolated in the northern region of the LMC; it has a partial shell of thin filaments and some bright, patchy emission across the face of the remnant. N49, one of the brightest SNRs in the LMC, shows the strongest polarized emission in the west, where the total intensity is very weak, probably as a result of high magnetic field organization. N44:shell 3, on the northeastern edge of a very large H II region complex, is definitely confirmed as an SNR but has a different central position and outline at radio wavelengths than it does at X-ray wavelengths.