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A synthetic view at large scale of local molecular clouds

  • F. Lebrun
Part I: Nearby Molecular Clouds as Part of Larger Structure
Part of the Lecture Notes in Physics book series (LNP, volume 237)

Abstract

Local molecular clouds can be studied in many ways at various wavelenghts from radio waves to γ rays. None of these observations leads alone to a single and unambigous interpretation. Simplifying assumptions are generarally made which limit the degree of confidence of the results obtained. As an example it is often assumed, especially in the local interstellar medium, that some quantities are constant. Among them I can list, the gas to dust ratio, N(H2)/Wco ratio, the HI spin temperature, the cosmic-ray density, etc...

Synthetic studies may then help resolving some of the ambiguities resulting from these assumptions. An example is discussed based on the comparison of galaxy counts, ~ rays, U-V absorption lines, CO, star counts and reddening. Furthermore, these observations are also very often complementary. The 21 cm sky surveys provide an accurate and nearly fully sampled map of atomic hydrogen, but does not depict the H2 distribution. Gamma rays can trace both species but are not very accurate. The reddening measurements cannot provide a fully sample sky survey and are also not very accurate but are probably the only way of estimating cloud distances in the solar neighbourhood (d < 500 pc), which are essential for estimating sizes and masses.

Keywords

Column Density Solar Neighbourhood Spin Temperature Gould Belt Local Interstellar Medium 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • F. Lebrun
    • 1
  1. 1.Service d'Astrophysique, C.E.N. SaclayGif/Yvette CEDEXFrance

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