2021ApJS..253...15L

We present a study of molecular outflows using six molecular lines (including ¹²CO/¹³CO/C¹⁸O/HCO⁺ (J = 1-0) and CS/SiO (J = 2-1)) toward nine nearby high-mass star-forming regions with accurate known distances. This work is based on the high-sensitivity observations obtained with the 14 m millimeter telescope of the Purple Mountain Observatory in Delingha. The detection rate of outflows (including ¹²CO, ¹³CO, HCO⁺, and CS) is 100%. However, the emission of SiO was not detected for all sources. The full line widths (ΔV) at 3σ above the baseline of these molecular lines have the relationship ΔV_^12CO> ΔV_HCO⁺ > ΔV_CS~ΔV_^13CO> ΔV_^18CO. ¹²CO and HCO⁺ can be used to trace relatively high-velocity outflows, while ¹³CO and CS can be employed to trace relatively low-velocity outflows. The dynamical timescales of the ¹³CO and CS outflows are longer than those of the ¹²CO and HCO⁺ outflows. The mechanical luminosities, masses, mass-loss rates and forces of all outflows (including ¹²CO, ¹³CO, HCO⁺, and CS) are correlated with the bolometric luminosities of their central IRAS sources.