be valid for X-ray irradiated small clumps too. Now if we assume that the clump has the line-of-sight extent similar to the extent on the sky ($\sim 0.'5$), then $ \Omega_{\rm cl}/4\pi \sim 4 \times 10^{-3}$. Since the X-ray luminosity of 11p2 is $L_X\sim 10^{36}$ erg s$^{-1}$ in 0.6–10 keV band [@vas96], we have $L_{2.122}\simlt 4 \times 10^{30} $ erg s$^{-1}$. This is much less than the observed 212 luminosity of the SE filament, which is $\sim 6 \times 10^{33}$ erg s$^{-1}$. Therefore, the X-ray excitation/heating does not appear to be important for the -SE filament.

The above consideration leads us to conclude that the -SE filament is excited by the SNR shock associated with 11p2. The absence of associated 164 or emission suggests that the emission from the -SE filament might be from warm molecules swept-up by a slow, non-dissociative $C$ shock not from reformed molecules behind a fast, dissociative $J$ shock. The critical velocity for a shock to be a non-dissociative $C$ shock is $\simlt 50$  [@dra83; @mck84]. The dereddened mean surface brightness of the -SE filament is $\sim 8\times 10^{-4}$ erg cm$^{-2}$ s$^{-1}$ sr$^{-1}$. This is comparable to the (normal) brightness of a $\sim 30$  shock propagating 