Gas kinematics and the Dragged Magnetic Field in the High-mass Molecular Outflow Source G192.16$-$3.84: An SMA View

TL;DR

This study uses SMA observations to analyze gas kinematics and magnetic fields in the high-mass star-forming region G192.16-3.84, revealing a rotating disk, high-velocity jet, and magnetic field structures influenced by gravitational rotation.

Contribution

First detailed SMA polarization and molecular line study of G192.16-3.84 revealing magnetic field dragging and gas dynamics in a high-mass star-forming region.

Findings

Dense gas is spinning-up, marginally bound by ~11-25 M_sun.

High-velocity jet and expanding cavity detected in CO 3-2.

Magnetic fields are toroidal and aligned with the disk, dragged by rotation.

Abstract

We report the Submillimeter Array (SMA) observations of the polarized 0.88\,mm thermal dust emission and various molecular line transitions toward the early B-type ($L_{*}\sim2\times10^{3}L_{\odot}$) star-forming region G192.16$-$3.84 (IRAS 05553+1631). The peak of the continuum Stokes-I emission coincides with a hot rotating disk/envelope (SO$_{2}$ rotational temperature T$_{rot}^{SO_{2}}$$\sim84^{+18}_{-13}$\,K), with a north-south velocity gradient. Joint analysis of the rotation curve traced by HCO$^{+}$ 4-3 and SO$_{2}$ 19$_{1,19}-18_{0,18}$ suggests that the dense molecular gas is undergoing a spinning-up rotation, marginally bound by the gravitational force of \textbf{an} enclosed mass $M_{*+gas+dust}\sim$11.2-25.2\,$M_{\odot}$. Perpendicular to the rotational plane a $\gtrsim100/\cos(i)$\,km\,s$^{-1}$ ($i\sim63^{\circ}$) high velocity molecular jet, and the $\sim$15-20\,km\,s$^{-1}$ expanding biconical cavity were revealed in the CO 3-2 emission. The polarization percentage of the 0.88\,mm continuum emission decreases toward the central rotating disk/envelope. The polarization angle in the inner $\sim2"$ (0.015\,pc) disk/envelope is perpendicular to the plane of the rotation. The magnetic field lines, which are predominantly in the toroidal direction along the disk plane, are likely to be dragged by the gravitationally accelerated rotation.