Wide Integral-Field Infrared Spectroscopy of the Bright [Fe II] Shell in the Young Supernova Remnant G11.2-0.3

TL;DR

This study uses wide-field near-infrared spectroscopy to analyze the [Fe II] shell of supernova remnant G11.2-0.3, revealing detailed physical properties, shock dynamics, and evidence of episodic mass loss from the progenitor star.

Contribution

It provides the first detailed spatially-resolved analysis of the [Fe II] shell in G11.2-0.3, including electron density, extinction, and shock properties, along with discovery of a high-velocity component.

Findings

Electron density estimated at 4,700-9,400 cm^-3

Discovery of a faint high-velocity (~ -440 km/s) component

Shell composed of multiple thin filaments from episodic mass loss

Abstract

We present the results of wide integral-field near-infrared (1.0-1.8 um) spectroscopic observations of the southeastern shell of the young core-collapse supernova remnant (SNR) G11.2-0.3. We first construct [Fe II] 1.644 um line images of three bright clumps from the obtained spectral image cubes and compare them with those of other transitions such as [Fe II] 1.257, [Fe II] 1.534 and He I 1.083 um line images. This allows us to estimate the electron density (~ 4,700-9,400 cm^-3) and extinction (Av ~ 16-20 mag) of the shell, including detailed two-dimensional distribution of the properties in the brightest clump, as well as the discovery of a faint high-velocity (~ -440 km/s) component in the clump. Our SNR shock model calculations estimate the preshock number density of ~ 250-500 cm^-3 and shock speed of ~ 80-250 km/s in the [Fe II]-emitting region of the SNR. The comparison between the observed and modelled radial profiles of the line intensities and their ratios reveals that the shell is composed of multiple thin filaments which have been likely formed in episodic mass loss processes of a progenitor star. The discovery of the faint high-velocity component supports the interpretation that the southeastern shell of G11.2-0.3 is mainly composed of circumstellar material with contamination by supernova ejecta and also that its ejected material was expelled primarily in the southeast-northwest direction.