A new molecular hydrogen outflow in Serpens

We report the discovery of a new molecular hydrogen outflow in the Serpens molecular cloud. Narrowband filter images taken in the 2.12 mu m v = 1-0 S(1) transition of H-2 and adjacent continuum reveal a series of bright knots of pure line emission apparently emerging to the north-northwest from the embedded source SMM-3 and passing close to the visible star CK-8. Low-resolution H-and K-band spectra of the region show more than a dozen distinct H-2 transitions, whose strength ratios point to shock heating with T-exc similar to 2000 K. Echelle spectra of the S(1) transition with 20 km s(-1) resolution reveal unusual kinematics: the line center velocity increases linearly with distance to the north-northwest from SMM-3 until the bright knots of emission, at which point the velocity begins dropping to a fraction of its maximum value. The molecular hydrogen emission likely arises in limb-brightened bow shocks as a jet from SMM-3 encounters the ambient molecular cloud. This scenario is strengthened by recent HCO+ and SiO submillimeter observations of SMM-3, which show an apparent outflow corresponding to the H-2 structures.