A 1000 AU Rotating Disk around the Massive Young Stellar Object G192.16−3.82

Abstract

We present evidence for a circumstellar disk around the luminous young stellar object G192.16-3.82. Observations of 2.6 mm, 7 mm, and 3.6 cm continuum emission and 13CO, C18O, and H2O maser line emission support the interpretation that a 1000 AU rotating disk exists around the central B2 star. The disk major axis is roughly perpendicular to the outflow, and the maser velocities are consistent with Keplerian rotation. The mass of the disk plus circumstellar envelope traced by millimeter continuum emission is ~15 M☉. The source is embedded in a 500 M☉ molecular cloud from which a massive outflow emerges. Updated outflow parameters yield a total flow mass of 95 M☉ and a mass flow rate of 5.6 × 10-4 M☉ yr-1. The outflow opening angle, defined by a 13CO shell, is approximately 90°. A weak, one-sided, ionized jet emanates from the young stellar object system. The estimated momentum rate of the jet (~10-3 M☉ km s-1 yr-1) is about a factor of 4 too low to power the flow. These results are consistent with the idea that the G192.16 outflow mechanism can be best characterized by a combination of a weak jet and a strong, wide-angle wind. Approximately 05 to the north of G192.16-3.82 is a band of 3.6 cm continuum emission and redshifted H2O maser components which we interpret to be due to a newly discovered jet from the embedded object G192.16-3.82 N. The jet does not affect the dynamics of the massive outflow significantly which indicates that it is probably due to a low-mass young stellar object.