Estimate of the free-free contribution at 3 mm (Eq. 3). In all panels, the SPR2 3 mm continuum is shown in contours. The dotted black contour marks the −5σ_cort level. The solid black contours start at 5σ_cont, and contour steps increase by a factor of 2 (e.g., 5, 10, 20, 40σ_cort). The top panels show in color the H(40)α peak intensity, integrated intensity, and line width derived from the second moment. The bottom panels show in color the SPR2 3 mm continuum (dust + ff), 3 mm ff continuum (estimated using Eq. 3), and 3 mm dust continuum. The synthesized beam size of the continuum and line data are shown in the bottom-left corner in black and red, respectively. In all panels, the area where the H(40)α integrated intensity and SPR2 continuum have a S/N < 5 are masked. The continuum fragments are classified into dust cores (red), dust+ff cores (orange), and cometary UCHII regions (cyan), further explained in Sect. 4.1. Fragments with S/N < 15 are not analyzed in this study and are labeled in gray.