Central velocity of the best fit for each spectra in the H₂CO line emission, together with the streamline model for H₂CO. The red and blue lines represent the best streamline model for an envelope mass of 0.18 M_⊙ (total central mass of 2.47 M_⊙) and 0.39 M_⊙ (total mass of 2.68 M_⊙), respectively. Left: central velocities with respect to position in the sky. The black polygon represents the region where velocities are sampled to build the kernel density estimation (KDE). The primary beam FWHM size is represented with a dashed white circle. The beam size is represented by a black ellipse in the bottom left corner. Right: central velocity KDE as a function of projected distance to Per-emb-50 is plotted in grayscale. The KDE levels are drawn from 0.5σ in steps of 0.5σ, where the σ level is equivalent to the standard deviation of a normalized bivariate normal distribution. The horizontal dashed line represents the central velocity of Per-emb-50 V_LSR = 7.5 km s⁻¹. The centrifugal radius resulting from each envelope mass are located below the curve.