Outflows and Luminous YSOs: A New Perspective on the G192.16 Massive Bipolar Outflow

Abstract

We have obtained new observations of the massive molecular outflow in G192.16-3.82 in CO(J = 1-0) line and 3 mm continuum using the Owens Valley Radio Observatory millimeter-wave array. We have also imaged the outflow in the near-infrared J, H, and K bands and 2.12 μm H2 at Lowell Observatory and in the Ks band at the Apache Point Observatory. A large-field Palomar image shows that the outflow structure may extend more than 4 pc from the young stellar object (YSO), making it one of the largest known Galactic outflows. There is approximately 80 M☉ of molecular material in the high-velocity flow, and the mass flow rate is ~5 × 10-4 M☉ yr-1. The flow appears to be driven by an early-B star that is surrounded by approximately 17 M☉ of material. A biconical infrared reflection nebula is centered near the millimeter continuum peak, and shock-excited H2 emission is detected at the brightest peak in the K-band reflection nebula. H2 emission is also detected just beyond the highest velocity gas in the blueshifted CO outflow. The slope of the mass spectrum is approximately -2 at velocities below 15 km s-1 and decreases to as low as -8 at higher velocities. This is significantly steeper than in low-mass outflows, suggesting that the powering mechanism is less efficient at accelerating material in the flow. Alternatively, the outflow may have built up a substantial reservoir of low-velocity gas that steepens the mass spectrum. The observation of a wide outflow opening angle (~60°) and limb-brightened shell surrounding the high-velocity gas, together with shock-excited H2 emission and large bow shocks that extend up to 4 pc from the YSO, are consistent with the presence of both a poorly collimated disk-wind and a jet.