Millimeter- and Submillimeter-Wave Observations of the OMC-2/3 Region. II. Observational Evidence for Outflow-triggered Star Formation in the OMC-2 FIR 3/4 Region

We have observed the Orion Molecular Cloud-2 FIR 3/4 region in the H¹³CO⁺ (J = 1–0),¹²CO (J = 1–0), SiO (v = 0, J = 2–1), and CS (J = 2–1) lines and the 3.3 mm continuum emission with the Nobeyama Millimeter Array (NMA) and in the CO (J = 3–2) and CH₃OH (J_K = 7_K–6_K) lines with Atacama Submillimeter Telescope Experiment (ASTE). Our NMA observations in the H¹³CO⁺ emission have revealed 0.07 pc scale dense gas associated with FIR 4 (FIR 4 clump). The ¹²CO (J = 3–2,1-0) emission shows high-velocity blue- and redshifted components to both the northeast and southwest of FIR 3, suggesting an outflow from FIR 3 along the plane of the sky. The SiO and CH₃OH emission, known as shock tracers, are detected around the interface between the outflow and FIR 4 clump. Furthermore, the ¹²CO (J = 1–0) emission shows an L-shaped structure in the PV diagram. These results suggest the presence of an interaction between the outflow and FIR 4 clump. Moreover, our interferometric 3.3 mm continuum observations have first found that FIR 4 consists of 11 dusty cores at a scale of ~2000 AU. The separation among these cores (~5 × 10³ AU) is on the same order of the Jeans length (~13 × 10³ AU), and the estimated time scale of the fragmentation (~3.8 × 10⁴ yr) is similar to the time scale of the outflow interaction (~1.4 × 10⁴ yr). We suggest that the interaction triggered the fragmentation into these dusty cores, and hence the next generation of the cluster formation in FIR 4.