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The mass spectrum of interstellar clouds

  • John M. Dickey
  • R. W. Garwood
The Structure Of The Interstellar Medium
Part of the Lecture Notes in Physics book series (LNP, volume 350)

Abstract

The abundance of 21-cm absorption lines seen in surveys at high latitudes can be translated into a line of sight abundance of clouds vs. column density using an empirical relationship between temperature and optical depth. As VLA surveys of 21-cm absorption at low latitudes are now becoming available, it is possible to study the variation of this function with galactic radius. It is interesting to compare the abundance of these diffuse atomic clouds (with temperatures of 50 to 100 K and masses of 1 to 10 M) to the abundance of molecular clouds. To do the latter we must make assumptions about cloud cross-sections in order to convert the line of sight abundance of diffuse clouds into a number per unit volume, and to convert from cloud column density to mass. The spectrum of diffuse clouds matches fairly well the spectrum of molecular clouds, although observationally there is a gap of several orders of magnitude in cloud mass. Optical absorption studies also agree well with the 21-cm results for clouds of column density a few times 1020 M.

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References

  1. Burton, W.B., 1988, in Galactic and Extragalactic Radio Astronomy, 2nd Ed., G.L. Verschuur and K.I. Kellerman (Heidelberg: Springer Verlag).Google Scholar
  2. Colgan, S.W.J, Salpeter, E.E., and Terzian, Y., 1988, Ap. J. 328, 275.CrossRefADSGoogle Scholar
  3. Crovisier, J., 1981, Astron. Astrop. 94, 162.ADSGoogle Scholar
  4. Elmegreen, B., 1987, in Interstellar Processes, ed. D. Hollenbach and H. Thronson, (Dordrecht: Reidel) p. 259.Google Scholar
  5. Garwood, R.W., and Dickey, J.M., 1989, Ap. J. 338, 841.CrossRefADSGoogle Scholar
  6. Heiles, C., 1967, Ap. J. Supp. 15, 97.CrossRefADSGoogle Scholar
  7. Hobbs, L., 1974, Ap. J. 191, 395.CrossRefADSGoogle Scholar
  8. Jenkins, E.B., Jura, M., and Loewenstein, M., 1983, Ap. J. 270, 88.CrossRefADSGoogle Scholar
  9. Kulkarni, S.R., and Heiles, C.E., 1987, in Interstellar Processes, ed. D. Hollenbach and H. Thronson, (Dordrecht: Reidel) p. 87.Google Scholar
  10. Kulkarni, S.R., and Heiles, C.E., 1988, in Galactic and Extragalactic Radio Astronomy, 2nd Ed., G.L. Verschuur and K.I. Kellerman, (Heidelberg: Springer Verlag) pp. 95–153.Google Scholar
  11. Liszt, H.S., 1983, Ap. J. 275, 163.CrossRefADSGoogle Scholar
  12. Magnani, L., Blitz, L., and Wouterloot, J.G.A., 1988, Ap. J. 326, 909.CrossRefADSGoogle Scholar
  13. Mebold, U., Winnberg, A., Kalberla, P.M.W., and Goss, W.M., 1982, Astron. Astrop. 115, 223.ADSGoogle Scholar
  14. Payne, H.E., Salpeter, E.E., and Terzian, Y., 1983, Ap. J. 272, 540.CrossRefADSGoogle Scholar
  15. Scoville, N.Z. and Sanders, D.B., 1987, in Interstellar Processes, ed. D. Hollenbach and H. Thronson, (Dordrecht: Reidel), p. 21.Google Scholar
  16. Terebey, S., Fich, M., Blitz, L., and Henkel, C., 1987, Ap. J. 308, 357.CrossRefADSGoogle Scholar

Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • John M. Dickey
    • 1
    • 2
  • R. W. Garwood
    • 3
  1. 1.Sterrewacht LeidenThe Netherlands
  2. 2.University of MinnesotaUSA
  3. 3.University of PittsburghUSA

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