CO line emission from the globules. Blue (black) points correspond to the negative (positive) LSR velocity globules. Globule #6 lies close in velocity to the negative-v_LSR globules and indeed shows similar emission properties. Left panel: [C II]158 μm/¹²CO (2–1) line intensity ratio, in units of erg s⁻¹ cm⁻² sr⁻¹, as a functionof globule velocity centroid (as observed in ¹²CO). Right panel: ¹²CO/¹³CO (2–1) intensity ratio as a function of their line-width ratio. As gas column density raises, opacity broadening increases the width of ¹²CO lines. The dashed red line approximately marks the τ(¹²CO 2–1) >1 transition. Globules at the left of this line are not very thick in ¹²CO (2–1), yet they show very low ¹²CO/¹³CO(°2–1) line intensityratios produced by ¹³CO chemical fractionation.