Using Anisotropies as a Forensic Tool for Decoding Supernova Remnants

TL;DR

This paper introduces a spectral analysis method to distinguish between RTI-driven and explosion asymmetry-driven structures in supernova remnants, revealing insights into the ejecta density profile and explosion anisotropies.

Contribution

The study develops a power spectral analysis technique to identify the origins of structures in SNRs and links dominant angular modes to ejecta density profiles, advancing supernova remnant diagnostics.

Findings

Power spectrum identifies RTI-driven scales and explosion asymmetries.

Dominant angular mode relates to ejecta density scale height.

Structure larger than this mode indicates explosion anisotropy.

Abstract

We present a method for analyzing supernova remnants (SNRs) by diagnosing the drivers responsible for structure at different angular scales. First, we perform a suite of hydrodynamic models of the Rayleigh-Taylor instability (RTI) as a supernova collides with its surrounding medium. Using these models we demonstrate how power spectral analysis can be used to attribute which scales in a SNR are driven by RTI and which must be caused by intrinsic asymmetries in the initial explosion. We predict the power spectrum of turbulence driven by RTI and identify a dominant angular mode which represents the largest scale that efficiently grows via RTI. We find that this dominant mode relates to the density scale height in the ejecta, and therefore reveals the density profile of the SN ejecta. If there is significant structure in a SNR on angular scales larger than this mode, then it is likely caused by anisotropies in the explosion. Structure on angular scales smaller than the dominant mode exhibits a steep scaling with wavenumber, possibly too steep to be consistent with a turbulent cascade, and therefore might be determined by the saturation of RTI at different length scales (although systematic 3D studies are needed to investigate this). We also demonstrate, consistent with previous studies, that this power spectrum is independent of the magnitude and length scales of perturbations in the surrounding medium and therefore this diagnostic is unaffected by ``clumpiness" in the CSM.