A Multiwavelength Study of Outflows in OMC-2/3

Abstract

We present new v = 1–0 S(1) H2, 12CO J = 2 → 1, and 12CO J = 3 → 2 observations of the star-forming clouds OMC-2 and OMC-3, one of the densest known groupings of outflows from low-mass young stellar objects (YSOs) in the sky. High-velocity 12CO J = 2 → 1 gas in this region suggests that previously discovered H2 flows are driving and entraining molecular outflows. However, the large number of sources and flows within the narrow molecular filament means it is difficult to make a firm association of molecular outflow gas with H2 flows, except for in the case of the bipolar east-west H flow. A number of Herbig-Haro (HH) objects, including ones far to the west and east of the main ridge, are identified with H2 knots. High-resolution spectroscopy in the v = 1–0 S(1) line of 10 H2 knots shows line profiles consistent with dual forward and reverse shocks. C-shock modeling suggest that asymmetries seen in suspected bow shocks could be evidence of varying magnetic field orientations throughout the cloud. One of the bow shocks in the H flow, YBD-5, can be successfully modeled by a 100 km s-1 C-shock propagating into a magnetized, 106 cm-3 medium, although the observations and limitations within the computer code itself do not entirely rule out J-shocks. Mass spectra of the H flow are broken power laws, which might be evidence for a jet that has two entrainment mechanisms for accelerating ambient molecular gas into the outflow. The H2 luminosity in this flow is many times smaller than the CO mechanical luminosity, but this fact cannot rule out the possibility that a narrow highly collimated jet drives the molecular outflow, owing to uncertainties in extinction, outflow dynamic times, cooling contributions from other lines, and the wind model used. Outflows from OMC-2/3 are likely to contribute to the turbulent pumping of gas within the molecular ridge north of the Orion Nebula. High-velocity gas clumps north of the sources investigated here may represent evidence of additional undiscovered outflows from young stars.