Millimeter- and Submillimeter-Wave Observations of the OMC-2/3 Region. IV Interaction between the Outflow and the Dense Gas in the Cluster Forming Region of OMC-2 FIR 6

Abstract

Abstract We have conducted millimeter interferometric observations of the Orion Molecular Cloud-2 (OMC-2) FIR 6 region at an angular resolution of $\sim$ 4${}^{\prime\prime}$–7${}^{\prime\prime}$ with the Nobeyama Millimeter Array (NMA). In the 3.3-mm continuum emission we detected dusty core counterparts of previously identified FIR sources (FIR 6a, 6b, 6c, and 6d), and moreover resolved FIR 6a into three dusty cores. The size and mass of these cores are estimated to be 1100–5900 AU and 0.19–5.5$ M_{\odot}$, respectively. We found that in the $^{12}$CO ($J$$=$ 1–0) emission FIR 6b, 6c, and 6d eject molecular outflow, and that the FIR 6c outflow also exhibits at least two collimated jet-like components in SiO ($J$$=$ 2–1) emission. At the tip of one of the SiO components there appears an abrupt increase in the SiO line width ($\sim$ 15 km s$^{-1}$), where the three resolved cores in FIR 6a seem to delineate the tip. These results imply the presence of the interaction and a bowshock front between the FIR 6c molecular outflow and FIR 6a. If the interaction occurred after the formation of the FIR 6a cores, the influence of the FIR 6c outflow on the FIR 6a cores would be minimal, since the total gravitational force in the FIR 6a cores (1.0–7.7 $\times$ 10$^{-4} M_{\odot} $km s$^{-1}$yr$^{-1}$) is much larger than the outflow momentum flux (2.4 $\times$ 10$^{-5} M_{\odot} $km s$^{-1}$yr$^{-1}$). On the other hand, it is also possible that the interaction caused the gravitational instability in FIR 6a, and triggered the fragmentation into three cores, since the separation among these cores ($\sim$ 2.0 $\times$ 10$^{3} $AU) is on the same order of the Jeans length ($\sim$ 5.0–8.4 $\times$ 10$^{3} $AU). In either case, FIR 6a cores, with a mass of 0.18–1.6$ M_{\odot}$ and a density of 0.2–5.8 $\times$ 10$^{7} $cm$^{-3}$, might be potential formation sites of the next generation of cluster members.