Astronomy and Astrophysics – Astronomy
We present near-infrared imaging of IC443, covering the entire supernova remnant (50' diameter) from The Two Micron All Sky Survey (2MASS). 2MASS imaging is taken simultaneously in the J (1.25mu m), H (1.65mu m) and K_s (2.17mu m) bands using a 1.3 m telescope with a three-channel camera. The images have 3.5'' spatial resolution with a pixel size of 1''. The bands include lines of Pbeta , [Ni II] and [Fe II] for J band, Br10 and [Fe II] for H band, and Brgamma and H_2 for K_s band. Emission from IC443 was detected in all 3 bands from most of the optically bright parts of the remnant, revealing a shell-like morphology. This is the first near-infrared image of the northeastern and eastern parts. The color and structure are very different between the northeastern and southern parts. The northeastern shell shows sheet-like filamentary structure, similar to that of optical emission, with J and H band emission equivalently bright, and weak K_s emission. The H flux is higher than the K flux in the northeast; its ratio is similar order of magnitude to that of previously measured infrared spectroscopy from 2 positions. The ratio implies that the H band emission from the northeastern shell is mostly [Fe II] (1.64mu m), and the [Fe II] emission is much stronger than Brgamma . This contrasts to the ratio of 0.06 observed in H II regions. The strong [Fe II] line is produced not only by efficient excitation of Fe but also by grain destruction. Most of bright J band emission can be explained by hydrogen line of Pbeta (1.28mu m) when we estimate the expected intensity relative to Brgamma and Hα . In contrast, the south ridge is dominated by K_s band light with knotty structure, and has weak J and H band emission. The shocked H_2 line emission is well known from the sinus ridge produced by an interaction with dense molecular clouds. The large field of view of the 2MASS image shows that the H_2 emission extends to the east and inner shell of northeastern optical emission, which is abutting a molecular cloud shown in CO maps. This emission suggests that the interaction with the molecular clouds extends to the front side in the northeast as well as in the southern ridge. We also report ISO LWS observation of [O I] (63mu m) for 8 positions of the northeast. Strong lines were detected and peaked at the northeastern shell, where 2MASS image showed filametary structure in J and H. We will show results of diagnostics for molecular shocks combining 2MASS and ISO LWS data, discuss cooling in radiative shock, and compare the pre-shock ISM physical conditions between the northeast and south.
van Dyk Schuyler
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