A Unified Model for Bipolar Outflows from Young Stars: Kinematic Signatures of Jets, Winds, and Their Magnetic Interplay with the Ambient Toroids

Kinematic signatures of the jet, winds, multi-cavities, episodic shells arising in the unified model of bipolar outflows, where an outflow forms by radially-directed, wide-angle toroidally magnetized winds interacting with magnetized isothermal toroids, are extracted. The axial cylindrically-stratified density jet, as predicted in the cold X-wind model, carries a signature of broad profile near the base across the projected velocity of the wide-angle wind and narrows down along the axis with the collimated flow. The smooth self-similar hydrodynamic momentum-conserving shell forms a separate feature near the low velocity, and trace distinct curves of varying elliptic shapes in the position–velocity (PV) diagrams. The reverse shock enclosing the magnetized free wind, surrounded by the compressed wind, clearly forms an innermost cavity and alters the flow pattern and forms an oblique magnetized bubble under the outflow lobe. Shear, the Kelvin–Helmholtz instabilities, pseudo-pulses generated in the compressed magnetized wind and the compressed ambient add fine and distinctive structures to the PV diagrams between the jet–shell velocity components. The compressed ambient poloidal field can further complicate the low-velocity features with spur-like patterns. Apparent jet acceleration by magnetic forces stands out in PV toward the tip at the end of the thick compressed wind region. The self-similar hydromagnetic oblique bubble structures containing extended mixing layers are revealed by their kinematic signatures. Jet-like knotty structures and wide-angle cavities in the Class 0/I sources are finding their natural origins within this unified framework.

Schematic illustrations of the outflow interior structures resulting from the interplay of a magnetized wide-angle wind and a toroid threaded by strong (left) and weak (right) magnetic field.
Number density (shown in the left half of each panel) and column density (shown in the right half of each panel) of outflows with strong (left figure) and weak (right figure) ambient magnetic fields. Coordinates are shown self-similarly through normalizing by v0t.
Position–velocity diagrams of column density (PVDCD) of no-slip simulations along the outflow axis at various inclination angles, showing characteristic structures of jets and shells in the outflow lobes. An inclination of 90 degrees represents the outflows lying on the plane of the sky. PV diagrams are shown in terms of column density integrated over the line of sight. Coordinates are shown self-similarly through normalizing by v0t on the distance axis and by v0 on the velocity axis.
Comparisons between PV diagrams of column density of the no-vθ hydrodynamic calculations (top, vθ set to 0) and regular hydrodynamic simulations (bottom, with any vθ) for increasing toroid openings (left to right) at an inclination angle of 45 degrees. The momentum-conserved curves are overlaid as white dashed lines.
Gallery of PV diagrams of column density of outflows explored in the parameter space with various toroid openings, wind toroidal magnetization, and ambient poloidal magnetization. The distance is along the outflow axis at an inclination angle of 45 degrees. Coordinates are shown self-similarly through normalizing by v0t on the distance axis and by v0 on the velocity axis.
Transverse PV diagrams of column density perpendicular to the jet axis at various vertical locations of the outflow lobes at z/v0t = 0.05 (left column), 0.25 (central column), and 0.5 (right column). The diagrams are shown at an inclination angle of i = 90 degrees for poloidally magnetized ambient media (top panels) and non-magnetized ambient media (bottom panels) with increasing toroid opening (from left to right) and decreasing wind magnetizations (from top to bottom). The unshocked ambient material has been filtered out while producing the diagrams. For each n-column, an associated exaggeration factor magnifies transverse position (and/or velocity) to show detailed structures.

Related Publications

  • Shang H; Liu C-F; Krasnopolsky R; Wang L-Y, “A Unified Model for Bipolar Outflows from Young Stars: Kinematic Signatures of Jets, Winds, and Their Magnetic Interplay with the Ambient Toroids”, ApJ: 944(2), id.230 (55 pp), Feb, 2023 [SCI] ( ADS | Fulltext )
  • Shang H; Krasnopolsky R; Liu C-F; Wang L-Y;, “A Unified Model for Bipolar Outflows from Young Stars: The Interplay of Magnetized Wide-Angle Winds and Isothermal Toroids”, ApJ: 905(2), 116, Dec 20, 2020 [SCI] ( ADS | Fulltext )
  • Wang L-Y; Shang H; Krasnopolsky R; Chiang T-Y, “A Two-Temperature Model of Magnetized Protostellar Outflows”, ApJ: 815(1), 39, Dec 10, 2015 [SCI] ( ADS | Fulltext )
  • Shang H; Allen A; Li Z-Y; Liu C-F; Chou M-Y; Anderson J, “A Unified Model for Bipolar Outflows from Young Stars”, ApJ: 649(2), 845-855, Oct 1, 2006 [SCI] ( ADS | Fulltext )