Velocity position diagrams of the H₂CO(3_0,3−2_0,2), HDCO(4_1,4−3_1,3), D₂CO(4_0,4−3_0,3), and C¹⁸O(3 − 2) lines along the declination axis at Δα = 0′′. The molecule is indicated in each panel. The C¹⁸O(3 − 2) data are from Liseau et al. (2010). The vertical scale in each panel indicates the declination offset and the horizontal scale is the v_LSR velocity. The intensity scale in all four panels is T_mb.