Comparison between the observed C¹⁸O (1–0) line profile in L1498 (left panel) and L1517B (right panel) and our fiducial model towards the center each source. In each panel the black histograms show the observation, and the red curves show the predicted line profile. The vertical dashed lines indicate the source rest velocity (7.76 and 5.75 km s^-1 for L1498 and L1517B, respectively), as determined from Gaussian fits of the observed line profiles. Bad correlator channels around 6.8 km s^-1 have been masked.