FWHM of the broad velocity component identified in the ¹²CO J = 10–9 line profiles for each type of YSOs versus their bolometric luminosities. Low-mass Class 0 (LM0) sources are indicated with blue pluses, low-mass Class I (LMI) with black triangles, intermediate-mass (IM) YSOs with green asterisks and high-mass (HM) objects with red crosses. For the high-mass sources, the ¹²CO J = 3–2 width is used instead. The black dashed line indicates the linear function that fits the relation between the FWHM and the logarithm of L_bol.