Rotational temperatures of warm (E_up = 14 − 24) CO (top) and H₂O (bottom) as function of bolometric luminosity. Orange circles show YSOs from Green et al. (2013), Karska et al. (2013), and Manoj et al. (2013). Dark blue crosses show intermediate-mass YSOs from the WISH program and light blue diamonds high-mass YSOs from Karska et al. (2014a). A few sources with luminosities ~ 10²L_⊙ shown with orange crosses are from Manoj et al. (2013) and can also be regarded as intermediate-mass YSOs. Uncertainties of the CO and H₂O rotational temperatures are shown for L1641 S3 MMS1, which is representative of the sample.