Fig. 2 is the final star-subtracted image where we can see the detailed features of emission more clearly.

As in Fig. 1 (right), the extended filament within the southeastern SNR shell, -SE filament hereafter, is most prominent. The filament is composed of two bright, $30''$-long, elongated segments in the middle and two clumpy segments at the ends. The one at the southern end is a little bit apart from the other three. The total extent of the filament is $\sim 2.'5$. The filament is not very thin but has a width of $\simlt 10''$. Fig. 3 shows a detailed structure of the filament, where we have just masked out stars using the K-cont image in order to avoid any possible artifacts associated with the PSF photometric subtraction. We can see that the filament has a very good correlation with the radio shell both in morphology and brightness. The peak 164 surface brightness of the filament is $1.9 \pm 0.2\times 10^{-3}$ ergs cm$^{-2}$ s$^{-1}$ sr$^{-1}$, which is larger than any previously reported brightness of 164 filaments in other remnants, e.g., 1.1–3$\times 10^{-4}$ ergs cm$^{-2}$ s$^{-1}$ sr$^{-1}$ in IC 443 and Crab [@gra87; @gra90] or $1.5\times 10^{-3}$ ergs cm$^{-2}$ s$^{-1}$ sr$^{-1}$ in 