High resolution 36 GHz imaging of the Supernova Remnant of SN1987A

TL;DR

This paper presents high-resolution 36 GHz radio images of SN 1987A's remnant, revealing detailed morphology and spectral properties, extending the frequency coverage of ongoing monitoring to better understand the supernova's interaction with its environment.

Contribution

It provides the first high-resolution 36 GHz images of SN 1987A, bridging the gap between low and high-frequency observations, and models the remnant as a thick inclined torus.

Findings

Remnant has an elliptical ring morphology with enhanced emission regions.

Spectral index at 36 GHz is -0.83, indicating synchrotron emission.

Tentative detection of a central source with flatter spectral index.

Abstract

The aftermath of supernova (SN) 1987A continues to provide spectacular insights into the interaction between a SN blastwave and its circumstellar en- vironment. We here present 36 GHz observations from the Australia Telescope Compact Array of the radio remnant of SN 1987A. These new images, taken in 2008 Apr and 2008 Oct, substantially extend the frequency range of an ongo- ing monitoring and imaging program conducted between 1.4 and 20 GHz. Our 36.2 GHz images have a diffraction-limited angular resolution of 0.3-0.4 arcseconds, which covers the gap between high resolution, low dynamic range VLBI images of the remnant and low resolution, high dynamic range images at frequencies between 1 and 20 GHz. The radio morphology of the remnant at 36 GHz is an elliptical ring with enhanced emission on the eastern and western sides, similar to that seen previously at lower frequencies. Model fits to the data in the Fourier domain show that the emitting region is consistent with a thick inclined torus of mean radius 0.85 arcsec, and a 2008 Oct flux density of 27 +/- 6 mJy at 36.2 GHz. The spectral index for the remnant at this epoch, determined between 1.4 GHz and 36.2 GHz, is -0.83. There is tentative evidence for an unresolved central source with flatter spectral index.