Quantitative optical and near-infrared spectroscopy of H2 towards HH91A
Abstract
Aims:Optical and near-infrared spectroscopy of molecular hydrogen in interstellar shocks provide a very powerful probe of the physical conditions that prevail in interstellar shocks.
Methods: Integral-field spectroscopy of H2 in the optical wavelength region and complementary long-slit near-infrared spectroscopy towards
Results: The detection of some 200 ro-vibrational lines of molecular hydrogen ranging between 7700 Å and 2.3 μm is reported. Emission lines which arise from vibrational levels up to v' = 8 are detected. The H2 emission arises from thermally excited gas where the bulk of the material is at a temperature of 2750 K and where 1% is at 6000 K. The total column density of shocked molecular hydrogen is N(H2) = 1018 cm-2. Non-thermal excitation scenarios such as UV fluorescence do not contribute to the H2 excitation observed towards HH91A.
Conclusions: The emission of molecular hydrogen towards HH91A is explained in terms of a slow J-shock that propagates into a low-density medium, that has been swept up by previous episodes of outflows that have occurred in the evolved
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- November 2007
- DOI:
- 10.1051/0004-6361:20078260
- arXiv:
- arXiv:0709.0169
- Bibcode:
- 2007A&A...474..941G
- Keywords:
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- ISM: molecules;
- ISM: Herbig-Haro objects;
- ISM: jets and outflows;
- Astrophysics
- E-Print:
- A&