A New Molecular Hydrogen Outflow in Serpens

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Abstract
We report the discovery of a new molecular hydrogen outflow in the Serpens molecular cloud. Narrowband filter images taken in the 2.12 μm v = 1-0 S(1) transition of H2 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 H2 transitions, whose strength ratios point to shock heating with Texc ~ 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 H2 structures.