Contours and color-scale maps of integrated area toward a) MON R2, b) S156, c) DR17/L906, and d) M17/M18. The contour and color-scale map respectively represent the integrated intensities of the H₂CO and the mid-infrared 8.28 μm MSX emission in S156, DR17/L906, and M17/M18 regions. For the MON R2 region, the color-scale map represents the IRAS 12 μm data. a) For the MON R2 region: contour levels are –0.17 to –0.46 in steps of –0.06 K km s^-1. b) For the S156 region: contour levels are –0.09 to –0.25 in steps of –0.03 K km s^-1. c) For the DR17/L906 region: contour levels are –0.12 to –0.32 in steps of –0.04 K km s^-1. d) For the M17/M18 region: contour levels are –0.42 to –1.11 in steps of –0.14 K km s^-1.