H₂CO spectra and their spatial distribution atan angular resolution of 25″. Top: observed H₂CO (1_1,0−1_1,1) spectra of DR2l (a), DR22 (c), and G76.1883+0.0973 (e) overlaid on the fit results indicated by the dashed brown lines. The derived optical depth spectra are shown by the red lines. In panels a, c, e, the dashed vertical black lines represent the LSR velocities of the HII regions obtained from the radio recombination line measurements (Khan et al. in prep.). Bottom: VLA+Effelsberg 4.9 GHz radio continuum emission of DR2l (b), DR22 (d), and G76.1883+0.0973 (ƒ) overlaid with the H₂CO (1_1,0−1_1,1) absorption contours. For DR2l, the blue and red contours represent the H₂CO (1_1,0−1_1,0) absorption peak for the −3 km s⁻¹ and 8 km s⁻¹ components, respectively. The contours start at −0.1 Jy beam⁻¹ (5σ), with each subsequent contour being twice the previous one. For DR22 and G76.1883+0.0973, the contours start at −0.1 Jy beam⁻¹ (5σ) and decrease by 0.04 Jy beam⁻¹. The synthesized beam is shown in the lower left corner of each panel. All the continuum and spectral line data are from the combination of the VLA D configuration and the Effelsberg single-dish observations.