The jet/counter-jet symmetry of the HH 212 outflow

TL;DR

This paper analyzes the symmetry and dynamics of the HH 212 outflow, revealing jet/counterjet ejection timing, binary orbital motion, and proper motion velocities through infrared and optical imaging.

Contribution

It provides a detailed model of the outflow's symmetry, binary nature, and kinematic properties based on multi-wavelength observations.

Findings

Jet/counterjet knots are ejected with ~6-year time differences.

Binary orbital motion explains deviations in knot positions.

Proper motion velocities range from 50 to 170 km/s.

Abstract

We present Spitzer (IRAC) images observations and a VLT 2.1micron image of the HH 212 outflow. We find that this outflow has a strong symmetry, with jet/counterjet knot pairs with Delta x less than 1 arcsec position offsets. We deduce that the jet/counterjet knots are ejected with time differences Delta tau_0 approx. 6 yr and velocity differences Delta v_0~ 2 km/s. We also analyze the deviations of the knot positions perpendicular to the outflow axis, and interpret them in terms of a binary orbital motion of the outflow source. Through this model, we deduce a ~0.7M_solar mass for the outflow source, and a separation of ~80 AU between the components of the binary (assuming equal masses for the two components). Finally, using the IRAC data and the VLT 2.1micron image we have measured the proper motion velocities, obtaining values from 50 to 170km/s.