Astron. Astrophys. 344, 342-354 (1999)

5. Conclusions

The main conclusions from this work can be summarised as follows:

• ISO -LWS observations of the have revealed the presence of widespread [C II] 158 µm, [O I] 63 µm and FIR continuum emission.

• Our principal observational result is the correlation between the observed [C II] 158 µm flux and the projected distance to the B 2 star HD 147889. The flux dependence on the projected distance is shallower than an inverse square law.

• The observed angular distribution of the [C II] 158 µm line flux has enabled us to reconstruct the 3 D distribution of the line emitting regions in , showing that the cloud surface towards the putative energy source is concave.

• This model also provides an estimate of the local UV flux at the cloud ( 20-140) and of the degree of inhomogeneity of the cloud (0.2 filling of the 80" beam).

• From the comparison of the LWS data with detailed models of PDR s we infer that beam averaged particle densities in the thin surface layers ( a few magnitudes) of the are typically above 10⁴ cm^-3 but rarely as high as 10⁵ cm^-3.

• These models lend support to the the mass estimate of the core of the of Liseau et al. (1995), viz. 2 500 . For the known associated stellar mass content, the star formation efficiency is therefore 4%, i.e. significantly less than that commonly quoted in the literature.

© European Southern Observatory (ESO) 1999

Online publication: March 10, 1999
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