Position-velocity diagrams towards [GY92] 197, IRS 44 and IRAS 16253-2429. Blue and red dots represent blue- and red-shifted emission peaks above ±2 km s⁻¹, respectively, while green dots indicate velocities below ±2 km s⁻¹. Blue and red solid lines show the best fit for a Keplerian velocity profile with their respective errors, shown in dashed blue and red lines. The cut taken from the image data is shown in grey contours, ranging from 3σ (σ = 13 mJy beam⁻¹) to the maximum value of each transition. Each adjacent contour represents an increment of 30% of the maximum value for panels a and c, and an increment of 50% for panel b. The black dashed lines indicate the velocity above which the Keplerian profile was fitted. The solid black curves in panel c show the best fit for an infalling velocity profile.