Left: Measured [S II]/H α ratios represented by the color bar. The region includes SNRs IC 443 and the western part of G189.6 + 03.3. Two spectrum positions indicated by yellow arrows are α = 06h19m27.00s δ = +22d33′30.0″, and α = 06h17m49.70s δ = +22d01′25.3″. The strong [S II] emission suggests that these faint filaments belong to IC 443, rather than G189.6 + 03.3. Right: Same figure for [O III]/Hβ ratios. The [O III]/Hβ ratios are generally higher in the west and in the north compared to the east and the south.