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Astron. Astrophys. 330, 327-335 (1998)

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5. Conclusions

Our main conclusions from this work can briefly be summarized as follows:

  1. A 3D map (velocity being the third dimension) of the H [FORMULA] -flux, the level of excitation and the ne  have been derived. The strucure is very `clumpy' with densities going up to 104 cm-3  (maximum detectable with this method) and with spatial scales equal or smaller than the resolution [FORMULA]  2 [FORMULA]. The clump dispersion in velocity is of the order of 30 km s-1  to 50 km s-1. The clumps are found immersed in an `interclump medium' with ne   [FORMULA]  10 cm-3  - 300 cm-3.
  2. In HH 29 one can identify at least 6 separate features. Knots a - f are all well defined both morphologically and spectroscopically.
  3. Knots a, d, & e have a clear high excitation character while b & c are of the low excitation variety as derived from the [SII]/H [FORMULA]  ratio. Nevertheless, these two latter features have a relatively high value of their [OIII]/H [FORMULA]  ratio, indicating high excitation characteristics along the line-of-sight towards these objects. This is also strongly indicated by the change of ne  and level of excitation with velocity.
  4. The `clump' with the highest ne  and the largest F(H [FORMULA]) is HH 29a. The highest level of excitation is found in HH 29d.
  5. Both the high excitation knots and the low excitation knots have FWZI of [FORMULA]  230 km s-1  in H [FORMULA]. The peak velocity of the brightest peak varies for each of the features.
  6. The spectral characteristics and the position of the shock gradient with respect to the originating source for knots a, b, possibly c & f suggests them to be best explained by models of the `shocked cloudlet' type, i.e. a thinner faster wind that interacts with slower more dense material further out from the originating source. The observations of feature d instead indicates the opposite, i.e. denser material overtaking a thinner medium.
  7. A model based on these facts and which is consistent with the known characteristics of L1551 IRS5 including the structure of the L1551 molecular outflow, suggests HH 29 to be an aggreagate of denser clumps in the outflow plowing into either ambient material or a slower less dense wind component (perhaps older - IRS5 is known to have FU Orionis characteristics), at the same time being overtaken by a faster (thinner) wind.
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© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998