2015ApJS..221...31S

We performed the first spectral line survey at 82-106 GHz and 335-355 GHz toward the outflow-shocked region OMC 2-FIR 4, the outflow driving source FIR 3, and the northern outflow lobe FIR 3N. We detected 120 lines of 20 molecular species. The line profiles can be classified into two types: one type is a single Gaussian component with a narrow (<3 km/s) width, and the other type is two Gaussian components with narrow and wide (>3 km/s) widths. The narrow components for most of the lines are detected at all positions, suggesting that they trace the ambient dense gas. For CO, CS, HCN, and HCO⁺, the wide components are detected at all positions, suggesting an outflow origin. The wide components of C³⁴S, SO, SiO, H¹³CN, HC¹⁵N, H₂¹³CO, H₂CS, HC₃N, and CH₃ OH are only detected at FIR 4, suggesting an origin as outflow-shocked gas. The rotation diagram analysis revealed that the narrow components of C₂H and H¹³CO⁺ show low temperatures of 12.5±1.4 K, while the wide components show high temperatures of 20-70 K. This supports our interpretation that the wide components trace the outflow and/or outflow-shocked gas. We compared the observed molecular abundances relative to H¹³CO⁺ with those of the outflow-shocked region L 1157 B1 and the hot corino IRAS 16293-2422. Although we cannot exclude the possibility that the chemical enrichment in FIR 4 is caused by hot-core chemistry, the chemical compositions in FIR 4 are more similar to those in L 1157 B1 than those in IRAS 16293-2422.