Abstract
We present evidence for Lyα pumping of the Lyman band system of molecular hydrogen in Herbig-Haro 7 and the bipolar outflow DR 21. For this study we have measured several vibrational-rotational emission lines of H2 whose energy levels are widely spaced and ranging from 6000 (v = 1) to 25000 Kelvin (v = 4). We show that the near-infrared H2 emission from the shocked gas in HH 7 can be well described by a bow C-type shock. The enhanced emission observed from the higher energy levels (v > 3) can be well modelled by employing the Lyα pumping mechanism.
In the DR 21 outflow the multi-line study showed that different physical conditions exist in the eastern and western emission lobes. The higher H2 line ratios measured in the eastern lobe suggests a higher Lyα pump rate which may be locally produced in the fast bowshocks. The FUV radiation field emanating from the central HII regions may in addition be exciting the Lyman and Werner bands of H2 in the molecular lobes.
We show that the observed H2 emission can be interpreted in terms of a simple model consisting of a C-type bowshock, which produces the low excitation H2 emission, and a FUV radiation field with enough Lyα line radiation to produce the high excitation H2 emission through fluorescence.
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References
Allen, D. and Burton, M.: 1993,Nature 363, 54
Black, J. and Dalgarno, A.: 1976,Astrophys. J. 203, 132
Black, J. and van Dishoeck, E.: 1987,Astrophys. J. 322, 412,
Burton, M., Geballe, T., and Brand, P.: 1989,Mon. Not. R. Astron. Soc. 238, 1513
Burton, M., Hollenbach, D., and Tielens, A.: 1990,Astrophys. J. 365, 620,
Carr, J.: 1993,Astrophys. J. 406, 553
Fernandes, A.: 1993,Ph.D. thesis, University of Edinburgh
Fernandes, A. and Brand, P.: 1995,Mon. Not. R. Astron. Soc., accepted
Fernandes, A., Brand, P., and Burton, M.: 1995, in preparation
Fischer, J., Righini-Cohen, G., and Simon, M.: 1980,Astrophys. J., Lett. 238, L155
Fischer, J., Sanders, D., Simon, M., and Solomon, P.: 1985,Astrophys. J. 293, 508
Garden, R., Geballe, T., Gatley, I., and Nadeau, D.: 1986,Mon. Not. R. Astron. Soc. 220, 203
Garden, R., Russell, A., and Burton, M.: 1990,Astrophys. J. 354, 232
Hartigan, P., Raymond, J., and Hartmann, L.: 1987,Astrophys. J. 316, 323
Harvey, P., Joy, M., Lester, D., and Wilking, B.: 1986,Astrophys. J. 301, 346
Herbig, G. and Jones, B.: 1983,Astron. J. 88, 1040
Raymond, J., Hartigan, P., and Hartmann, L.: 1988,Astrophys. J. 326, 323
Reipurth, B., Raga, A., and Heathcote, S.: 1992,Astrophys. J. 392, 145
Schwartz, R.: 1983a,Ann. Rev. Astron. Astrophys. 21, p. 209,
Schwartz, R.: 1983b,Astrophys. J., Lett. 268, L37
Schwartz, R., Cohen, M., and Williams, P.: 1988,Astrophys. J. 333, 1035
Shull, J. and Draine, B.: 1987,Interstellar Processes, D. Reidel Publishing Company:Dordrecht, p283,
Smith, M. and Brand, P.: 1990,Mon. Not. R. Astron. Soc. 245, 108
Smith, M., Brand, P., and Moorhouse, A.: 1991,Mon. Not. R. Astron. Soc. 248, 451
Solf, J. and Böhm, K.: 1987,Astrophys. J. 93, 1172
Walther, D., Geballe, T., and Robson, E.: 1991,Astrophys. J. 377, 246
Wolfire, C. and Königl, A.: 1991,Astrophys. J. 383, 205
Zinnecker, H., Mundt, R., Geballe, T., and Zealey, W.: 1989,Astrophys. J. 342, 337
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Fernandes, A., Brand, P. & Burton, M. H2 fluorescence in HH 7 and DR 21. Astrophys Space Sci 233, 45–50 (1995). https://doi.org/10.1007/BF00627329
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DOI: https://doi.org/10.1007/BF00627329