A multispectral analysis of the northeastern shell of IC 443

Abstract

We have carried out optical observations of the north-eastern part of the supernova remnant IC 443 using the CFHT imaging spectrograph SITELLE. The observations consist of three multispectral cubes covering an 11$^{\prime}$ $\times$11$^{\prime}$ area allowing the investigation of both the spatial and spectral variation of 9 emission lines : [OII] $\lambda\lambda$3726+3729, [OIII] $\lambda\lambda$4959,5007, H$\beta$, H$\alpha$, [NII] $\lambda\lambda$6548,6583 and [SII] $\lambda\lambda$6716,6731. Extinction measurement from the H$\alpha$ / H$\beta$ ratio shows significant variation across the observed region with E(B-V) = 0.8-1.1. Electron density measurements using [SII] lines indicate densities ranging from 100 up to 2500 cm$^{-3}$. Models computed with the shock modelling code MAPPINGS are presented and compared with the observations. A combination of complete shock model and truncated ones are required in order to explain the observed spectrum. The shock velocities found in IC 443 are between 20 and 150 km/s with 75 km/s being the most prominent velocity. The pre-shock number density varies from 20 to 60 cm$^{-3}$. A single set of abundances close to solar values combined with varying shock parameters (shock velocity, pre-shock density and shock age) are sufficient to explain to great variation of lines intensities observed in IC 443. Despite the relatively modest spectral resolution of the data (R$\sim 1500$ at H$\alpha$), we clearly separate the red and blue velocity components of the expanding nebula, which show significant morphological differences.