Expanding Ejecta in the Oxygen-Rich Supernova Remnant G292.0+1.8: Direct Measurement through Proper Motions

TL;DR

This study measures proper motions of ejecta filaments in supernova remnant G292.0+1.8 over 21 years, revealing expansion dynamics, an estimated age of about 3000 years, and evidence for a bipolar explosion.

Contribution

First direct measurement of ejecta proper motions in G292.0+1.8 using multi-epoch imaging, providing insights into its expansion and explosion geometry.

Findings

Proper motions of filaments are 20-100 mas, consistent with free expansion.

Expansion center determined at specific coordinates, age estimated at 2990 years.

Ejecta distribution suggests a bipolar explosion mechanism.

Abstract

We report here the first study of proper motions of fast filaments in the young, oxygen-rich supernova remnant G292.0+1.8, carried out using a series of [O III] 5007 A emission-line images taken over a period of more than 21 years. Images taken at seven epochs from 1986 to 2008, all from telescopes at the Cerro Tololo Inter-American Observatory, show oxygen-emitting filaments, presumably ejecta fragments, throughout most of the remnant. We have measured the proper motions for 67 discrete filaments through two-dimensional correlations between images from different epochs. While the motions are small, mostly 20 to 100 milli-arcsec, they are nevertheless measurable through a robust technique of averaging measurements from many epoch pairs. The data are qualitatively consistent with a free-expansion model, and clearly show systematic motions outward from a point near the center of the radio/X-ray shell. Global fits using this model indicate an expansion center at R.A.(2000.0) = 11:24:34.4, Dec.(2000.0) = -59:15:51, and a kinematic age of 2990+-60 years. The young pulsar PSR J1124-5916 is located 46 arcsec southeast of the expansion center. Assuming that it was launched by the supernova, we expect the pulsar to be moving southeastward at 16 milli-arcsec, or a transverse velocity of 440 km/s. We find the fastest ejecta along an axis oriented roughly N-S in the plane of the sky, suggesting that a bipolar explosion produced G292.0+1.8, as appears to have been the case for Cas A.