THE JET/COUNTERJET SYMMETRY OF THE HH 212 OUTFLOW

We present Spitzer (IRAC) images and a VLT 2.1 mu m image of the HH 212 outflow. We find that this outflow has a strong symmetry, with jet/counterjet knot pairs with Delta x < 1 '' position offsets. We deduce that the jet/counterjet knots are ejected with time differences Delta tau 0 approximate to 6 yr and velocity differences Delta(v0) approximate to 2 km s(-1). 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 approximate to 0.7 M-circle dot mass for the outflow source, and a separation of approximate to 80 AU between the components of the binary (assuming equal masses for the two components). Finally, using the IRAC data and the VLT 2.1 mu m image we measure the proper motion velocities, obtaining values from 50 to 170 km s(-1).