Correlations between luminosities of FIR CO and [O I] lines. Top: correlation between the luminosities of the 63 and 145 μm [O I] lines at from LM to HM YSOs. Cores A and B in Gy 3–7 are marked as grey diamonds, Class 0 and Class I YSOs as orange "×" signs and red circles (Karska et al. 2018), respectively, IM YSOs as blue circles (Matuszak et al. 2015), and HM YSOs as green squares, respectively (Karska et al. 2014a). Black solid line is the linear fit to all sources except for the HM YSOs, showing a strong correlation between the two [O I] line luminosities. Bottom: correlation between luminosities of the CO lines and the [O I] line at 145 μm. Black solid line shows the linear fit to all sources, including the HM YSOs.