Top row: difference in υ_peak between the H₂CO (1_0,1 − 0_0,0) line and the three higher J-transitions of H₂CO. The X (in the y-axis) denotes the υ_peak noted in the x-axis. Bottom row: linewidths of the different H₂CO transitions. In top and bottom rows, sources in Cygnus-X are shown in purple, GLOSTAR sources in orange, and M8 sources in blue. The black symbols indicate clumps that do not satisfy the velocity criterion (green shaded region) and were excluded from further analysis.