Three most commonly detected H I lines across our sample. We show them using two of our regions. Left: Line moment-zero maps. The channels used to integrate the emission are those encompassed by the line Gaussian fits in the right panels. Red apertures enclose the map area used to extract the spectra at the protostars shown in the right panels (upper insets), while the broader grey aperture (minus the central red aperture) was used to extract the spectra of the local background (right panels, lower insets). Right: Gaussian curves fit the line emission for both the protostar (red, upper inset) and backgrounds (grey, lower insets). We reproduced the Gaussian fits of the background in upper insets to allow comparisons with the protostar Gaussian fit. For some of the lines (middle row), a second Gaussian is required for fitting another nearby emission line. Other detected lines are shown in Figures A.2, A.3, and A.4.