Left upper: CH₃OCH₃ (3_2,2–3_1,3) EE (filled yellow) and Gaussian fitting profile (red line). The RMS is 0.33 mK at a velocity resolution of 23.04 km s⁻¹. Right upper: the four molecular transition lines (filled yellow), and their Gaussian fitting profiles, CH₃ CN (12₀–11₀) (red line), ¹³CO (2–1) (blue line), SO (5₆–4₅) (light blue), C¹⁸O (2–1) (pink line), and the combination of four components (green line). The RMS is 1.80 mK for ¹³ CO (2–1) at a velocity resolution of 21.52 km s⁻¹. Left lower: CH₃CN (12₀–11₀) (red line) overlaid with SO (5₆–4₅) (blue line). The pink window ranges the subtracted transition line ¹³CO (2–1). Since ¹³ CO (2–1) is not a perfect Gaussian profile, some residual emission of ¹³CO (2–1) is in the pinkwindow. The RMS is 2.38 mK for CH₃CN (12₀–11₀) at a velocity resolution of 28.65 km s⁻¹. Right lower: SO (5₅–4₄) (blue line filled yellow) overlaid with SO (5₆–4₅) (red line, divided by 4). The RMS is 0.79 mK for SO (5₅–4₄) at a velocity resolution of 22.04 km s⁻¹, while it is 2.22 mK for SO (5₆–4₅) at a velocity resolution of 28.75 km s⁻¹.