Asymmetric Ejecta Distribution of the Cygnus Loop revealed with Suzaku

TL;DR

This study used Suzaku observations to analyze the Cygnus Loop, revealing asymmetric distribution of ejecta elements, with more concentrated ejecta in the south, supporting recent supernova explosion models.

Contribution

It provides detailed spatial analysis of ejecta distribution in the Cygnus Loop, demonstrating asymmetry consistent with supernova explosion theories.

Findings

Ejecta are distributed inside a large area of the Cygnus Loop.

Ejecta of Si, S, and Fe are more abundant in the south than in the north.

Ejecta asymmetry aligns with recent supernova explosion models.

Abstract

We observed a linearly sliced area of the Cygnus Loop from the north-east to the south-west with Suzaku in seven pointings. After dividing the entire fields of view (FOV) into 119 cells, we extracted spectra from all of the cells and performed spectral analysis for them. We then applied both one- and two-component non-equilibrium ionization (NEI) models for all of the spectra, finding that almost all were significantly better fitted by the two-component NEI model rather than the one-component NEI model. Judging from the abundances, the high-kT_e component must be the ejecta component, while the low-kT_e component comes from the swept-up matter. Therefore, the ejecta turn out to be distributed inside a large area (at least our FOV) of the Cygnus Loop. We divided the entire FOV into northern and southern parts, and found that the ejecta distributions were asymmetric to the geometric center: the ejecta of Si, S, and Fe seem to be distributed more in the south than in the north of the Cygnus Loop by a factor of about 2. The degree of ejecta-asymmetry is consistent with that expected by recent supernova explosion models.