Structure and Kinematics of the HH 111 Jet

Narrow-band CCD images of the HH 111 optical jet complex obtained at the ESO 3.5-m New Technology Telescope under conditions of excellent (not greater than 0.8 arcsec FWHM) seeing are presented. These new images reveal the existence of a faint counterjet in the redshifted lobe of this bipolar outflow. The knot at the tip of the main jet is also identified as a further bow shock, in addition to the three already known in this problem. Performing a partial deconvolution of the seeing profile made it possible to resolve the knots in the trunk of the jet, which are found to have widths of about 0.8 arcsec, lengths of 0.8-1.1 arcsec, and separation-to-width ratios of 2-4. The first bright knot at the base of the jet is split in two, perpendicular to the jet. It is suggested that this structure is a ring of enhanced emission, viewed edge-on, such as might result from the passage of a puff of enhanced density through an oblique shock in the jet. It is believed that more powerful (recurrent) eruptive events, possibly related to FU Orionis-type activity, are responsible for the main bow shocks.