Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.650865
Title: Near-infrared spectroscopy of shocked molecular hydrogen in star formation regions
Author: Fernandes, A. J. L.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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Abstract:
The work presented in this thesis is devoted to the study of the physics of shock waves in the dense molecular cloud environments that are typical of star forming regions. The structure of these shock waves is analysed in terms of the two basic models: J-shock and C-shock. We have investigated the H2 emission properties from Herbig-Haro 7 and the DR21 bipolar outflow by measuring several spectral lines arising in the K band. These H2 lines cover a wide range in energy of the upper level (6000-25000 K) and enable a detailed study of the temperature distribution of the gas. The calculated column density ratios have been compared to J and C-shock models for different shock geometries. We have shown that current oblique J- and C-shock models fail to explain the observed H2 column density ratios. J-shock models fail to provide sufficient hot gas form behind the shock front and are not able to explain the large line intensities observed in the high-vibrational H2 lines. The line emission from the 6 positions observed within the HH 7 bow are shown to be consistent with a paraboloidal bow shock geometry, which however necessitates of an extra source of excitation of the high energy levels to explain the H2 line ratios. We present a study of the effects of the UV radiation field associated with the bow shock structure and show that a shock-induced Far-UV radiation field with a strength of G0 = 102-103, can account for the observed H2 line ratios. We suggest that shocks are responsible for the low-lying level excitation of the H2 molecule while Lyα resonance pumping is responsible for the high-excitation line emission.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.650865  DOI: Not available
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