a) CO excitation temperature T_ex assuming a beam filling factor η = 0.5 overlayed with contours of CO(3–2) integrated intensity. The positions of YSOs identified by Chen et al. (2010) are marked with asterisks, OB stars (earlier than B4) from Fariña et al. (2009) are marked with triangles, and OB star candidates from Nakajima et al. (2005), taken from Chen et al. (2010), are marked with circles. b) T_ex derived from the two [C i] lines overlayed with the contours of [C i] ³P₁–³P₀ integrated intensity. c) T_ex derived by assuming τ = 1 for the [C ii] emission overlayed with the contours of [C ii] integrated intensity.