SPITZER SPECTRAL LINE MAPPING OF PROTOSTELLAR OUTFLOWS. I. BASIC DATA AND OUTFLOW ENERGETICS

We report the results of spectroscopic mapping observations carried out toward protostellar outflows in the BHR71, L1157, L1448, NGC 2071, and VLA 1623 molecular regions using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations, covering the 5.2–37 μm spectral region, provide detailed maps of the eight lowest pure rotational lines of molecular hydrogen and of the [S i] 25.25 μm and [Fe ii] 26.0 μm fine-structure lines. The molecular hydrogen lines, believed to account for a large fraction of the radiative cooling from warm molecular gas that has been heated by a non-dissociative shock, allow the energetics of the outflows to be elucidated. Within the regions mapped toward these five outflow sources, total H2 luminosities ranging from 0.02 to 0.75 L☉ were inferred for the sum of the eight lowest pure rotational transitions. By contrast, the much weaker [Fe ii] 26.0 μm fine-structure transition traces faster, dissociative shocks; here, only a small fraction of the fast shock luminosity emerges as line radiation that can be detected with Spitzer/IRS.

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