The L1448 Molecular Jet

Abstract

We have obtained near-infrared images of the L1448 molecular outflow in the J, H, and K bands and through a 1% passband filter centered on the 2.122 microns V = 1-0 S(1) line of molecular hydrogen. We report the discovery of a highly collimated, clumpy, and bipolar molecular hydrogen jet associated with the L1448 molecular outflow. We estimate that the total H<SUB>2</SUB> luminosity of the L1448 outflow is about 0.2 L<SUB>sun</SUB>. Most of the line emission in the northern outflow lobe arises from a narrow, curving filament consisting of a chain of knots. Some H<SUB>2</SUB> knots and the bow-shaped emission regions protruding several arcseconds to the west of the filament may be shocks associated with CO- and SiO-emitting "bullets" seen in millimeter-wave observations. We interpret the H<SUB>2</SUB> emission in the context of a jet-driven model for molecular outflows. Bright H<SUB>2</SUB> emission near the molecular "bullets" may be produced by shocks propagating into the moving medium, while the extended and curving filament may be driven by expanding bow shocks in the wakes of the "bullets." A conical 2.2 microns continuum nebula extends from the driving source of the L1448 outflow toward the blueshifted outflow lobe. Several knots of H<SUB>2</SUB> emission to the northeast of the main L1448 H<SUB>2</SUB> filament may be associated with a separate outflow emerging from L1448 IRS 3, which we estimate has a total H<SUB>2</SUB> luminosity of about 0.01 L<SUB>sun</SUB>.