a) Three-color composite image of the 22 μm (red), the 12 μm (green) and 4.6 μm emission (blue) from WISE overlaid with the YSO distribution. b) Same as Fig. 3b, but overlaid with the YSO distribution. c) Same as Fig. 3c, but overlaid with the YSO distribution. The solid red ellipse represents S287 while the purple solid line marks the highest H₂ column density line of the filament S287-main along its long axis. d) Same as Fig. 3d, but overlaid with the YSO distribution. The dashed red ellipses represent shell A, shell B, and shell C. The purple arrow shows the overdensity of YSOs around the shells. In the four panels, the Class I and Class II YSOs are marked with white and cyan circles, while MSYOs are marked with red crosses.