Upper panel: spectrum of the SPW 5 in correspondence with the continuum peak in A1N. The strong and wide H30α line is labeled. Central panel: channel maps at different velocities across the H30α line width, showing the compact structure of the emission. The more diffuse emission is mostly due to two weak CH₃OCHO lines. In all panels, the green contour is the 5σ threshold (5 mJy beam⁻¹) of the ALMA 1.4 mm continuum. In the central panel, the white contours reproduce the JVLA A-Array 1.3 cm continuum, plotting levels from 0.1 to 16, by 3 mJy beam⁻¹. Lower panel: plot of channel VLSR vs. corresponding peak positions, projected along the major axis of the peak distribution at PA = 39°. Black vertical error bars are equal to the channel width of 0.6 km s−1; red horizontal error bars give the peak position errors, estimated with the expression (Reid et al. 1988): (Θ ∕2)(σ∕I), where Θ is the FWHM size of the observing beam, and I and σ are the peak intensity and the channel rms noise, respectively. The dashed line is a linear fit to the data. A lower limit to the size of the region harboring the VLSR gradient is indicated.