Radio-Continuum Emission From The Young Galactic Supernova Remnant G1.9+0.3

TL;DR

This study analyzes radio observations of the young supernova remnant G1.9+0.3, estimating its expansion, spectral index, polarization, and magnetic field, confirming its status as the youngest known remnant with a very strong magnetic field.

Contribution

It provides new radio-continuum measurements and estimates of the magnetic field and expansion rate for G1.9+0.3, enhancing understanding of young supernova remnants.

Findings

Estimated expansion rate of 0.563% per year.

Detected 6% polarized radio emission with peaks at 17%.

Magnetic field strength estimated at approximately 273 μG.

Abstract

We present an analysis of a new Australia Telescope Compact Array (ATCA) radio-continuum observation of supernova remnant (SNR) G1.9+0.3, which at an age of $\sim$181$\pm$25 years is the youngest known in the Galaxy. We analysed all available radio-continuum observations at 6-cm from the ATCA and the Very Large Array. Using this data we estimate an expansion rate for G1.9+0.3 of 0.563%$\pm$0.078% per year between 1984 and 2009. We note that in the 1980's G1.9+0.3 expanded somewhat slower (0.484% per year) than more recently (0.641% per year). We estimate that the average spectral index between 20-cm and 6-cm, across the entire SNR is $\alpha=-0.72\pm 0.26$ which is typical for younger SNRs. At 6-cm, we detect an average of 6% fractionally polarised radio emission with a peak of 17%$\pm$3%. The polarised emission follows the contours of the strongest of X-ray emission. Using the new equipartition formula we estimate a magnetic field strength of B$\approx 273\mu$G, which to date, is one of the highest magnetic field strength found for any SNR and consistent with G1.9+0.3 being a very young remnant. This magnetic field strength implies a minimum total energy of the synchrotron radiation of E$_{\textrm{min}} \approx$ 1.8$\times$10$^{48}$ ergs.