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G11.2$-$0.3 has been proposed to be a young remnant of an SN IIL/b interacting with a dense RSG wind based on its PWN and the small size of the SNR shell [@che05]. The thick, bright shell is thought to be shocked SN ejecta in contact with shocked wind material. The outer edge of the shell is not sharp and it was suggested that the ambient shock propagating into wind material could be at a larger distance [@gre88; @che05]. In the following, we first discuss the physical properties of the filaments that we have discovered in this paper, and show that our results support the SN IIL/b scenario. Then we discuss the physical properties of the filaments which are thought to be composed of both shocked wind material and shocked SN ejecta.

Filaments and Presupernova Circumstellar Wind
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### Excitation of filaments

The -SE filament is located at the rim of the bright SNR shell and elongated along the rim, which suggests that it is excited by the SNR shock. The derived $v=2$–1 excitation temperature ($\approx 2,100$ K) is also typical for shocked molecular gas [@bur89]. The dereddened peak 212 surface brightness is $1.3\pm 0.1 \times 10^{-3}$ erg cm$^{-2}$ s$^{-1}$ 