# Genus Statistic Applied to the X-ray Remnant of SN 1572: Clues to the Clumpy Ejecta Structure of Type Ia Supernovae

## TL;DR

This study uses the genus statistic to analyze X-ray images of Tycho's supernova remnant, providing evidence that its clumpy structure originates from initial explosion conditions rather than later hydrodynamic instabilities.

## Contribution

The paper demonstrates that the genus statistic can effectively distinguish between clumpiness caused by explosion physics and that from remnant evolution using 3D hydrodynamical simulations and X-ray observations.

## Key findings

- Genus curve of Tycho's SNR indicates non-Gaussian, skewed ejecta distribution.
- Simulation with initially clumped ejecta matches observed genus curve.
- Smooth ejecta simulation aligns with Gaussian random fields, unlike observations.

## Abstract

Clumpy structures are a common feature in X-ray images of young Type Ia supernova remnants (SNRs). Although the precise origin of such clumps remains unclear there are three generic possibilities: clumpiness imposed during the explosion, hydrodynamic instabilities that act during the remnant's evolution, and pre-existing structures in the ambient medium. In this article we focus on discriminating between clumping distributions that arise from the explosion and those from the remnant's evolution using existing 3D hydrodynamical simulations. We utilize the genus statistic for this discrimination, applying it to the simulations and {\it Chandra} X-ray observations of the well-known SN Ia remnant of SN 1572 (Tycho's SNR). The genus curve of Tycho's SNR strongly indicates a skewed non-Gaussian distribution of the ejecta clumps and is similar to the genus curve for the simulation with initially clumped ejecta. In contrast, the simulation of perfectly smooth ejecta where clumping arises from the action of hydrodynamic instabilities produced a genus curve that is similar to a random Gaussian field, but disagrees strongly with the genus curve of the observed image. Our results support a scenario in which the observed structure of SN Ia remnants arises from initial clumpiness in the explosion.