Hostname: page-component-586b7cd67f-g8jcs Total loading time: 0 Render date: 2024-11-25T18:27:04.309Z Has data issue: false hasContentIssue false
  • English
  • Français

General physical characteristics of the interstellar molecular gas

Published online by Cambridge University Press:  14 August 2015

B. E. Turner
B. E. Turner*
Affiliation:
National Radio Astronomy Observatory∗ Green Bank, West Virginia, U.S.A.

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The interstellar medium may be characterized by several physically rather distinct regimes: coronal gas, intercloud gas, diffuse clouds, isolated dark clouds and globules (of small to modest mass), more massive molecular clouds containing OB (and later) stars, and giant molecular clouds. Molecules first appear in the denser diffuse clouds, and occur everywhere that AV ≳ 1m. Values of temperature, density, ionization fraction, mass, size, and velocity field are discussed for each regime. Heating and cooling mechanisms are reviewed. Nearly all molecular clouds exceed the Jeans criteria for gravitational instability, yet detailed models reveal no cases where observations can be interpreted unambiguously in terms of rapid collapse. The possibility that clouds are supported by turbulence, rotation, or magnetic fields is discussed, and it is concluded that none of these agencies suffice. Comments are made about fragmentation and star formation in molecular clouds, with possible explanations for why only low mass stars form in low mass clouds, why early-type stars form only in clouds with masses ≳ 103 M⊙, and why O-stars seem to form near edges of clouds. Finally, large-scale interactions between molecular clouds and the galactic disk stellar population are discussed.

Type
V. PHYSICAL PROPERTIES OF THE INTERSTELLAR MEDIUM
Information
Symposium - International Astronomical Union , Volume 84: The Large-Scale Characteristics of the Galaxy , 1979 , pp. 257 - 270
Copyright
Copyright © Reidel 1979 

References

Arons, J., and Max, C. E.: 1975, Ap. J. (Letters) 196, L77.Google Scholar
Baran, G. P.: 1978, Ph.D. dissertation, Columbia U., in preparation.Google Scholar
Blair, G. N., Evans, N. J., vanden Bout, P. A., and Peters, W. L.: 1978, Ap. J. 219, 896.Google Scholar
Blitz, L.: 1978a, Ph.D. dissertation, Columbia U., in preparation.Google Scholar
Blitz, L.: 1978b, Conf. Proceedings on the Massive Molecular Clouds Workshop, Gregynog, Wales.Google Scholar
Bok, B. J.: 1977, P.A.S.P. 89, 597.Google Scholar
Bok, B. J., Cordwell, C. S., and Cromwell, R. H.: 1971, in Dark Nebulae, Globules, and Protostars, ed. Lynds, B. T., U. of Arizona Press.Google Scholar
Clark, F. O., Giguerre, P. T., and Crutcher, R. M.: 1977, Ap. J. 215, 511.Google Scholar
Cong, H. I. 1977, unpublished Ph.D. dissertation, Columbia U. Google Scholar
Crutcher, R. M., Evans, N. J., Troland, T., and Heiles, C.: 1975, Ap. J. 198, 91.Google Scholar
Dalgarno, A., and Oppenheimer, M.: 1974, Ap. J. 192, 597.Google Scholar
Davies, R. D., and Cummings, E. R.: 1975, M.N.R.A.S. 170, 95.Google Scholar
Dickman, R. L.: 1975, Ap. J. 202, 50.CrossRefGoogle Scholar
Dickman, R. L.: 1976, unpublished Ph.D. dissertation, Columbia U.Google Scholar
Disney, M. J., and Hopper, P. B.: 1975, M.N.R.A.S. 270, 177.Google Scholar
Elmegreen, B. G.: 1977, Conf. Proceedings of the Massive Molecular Clouds Workshop, Gregynog, Wales.Google Scholar
Elmegreen, B. G., and Lada, C. J.: 1976, A. J. 81, 1089.Google Scholar
Elmegreen, B. G., and Lada, C. J.: 1977, Ap. J. 214, 725.Google Scholar
Elmegreen, B. G., Lada, C. J., and Dickinson, D. F.: 1978, in preparation.Google Scholar
Evans, N. J., Blair, G. N., and Beckwith, S.: 1977, Ap. J. 217, 448.Google Scholar
Field, G. B.: 1978, in Proc. of Conf. on Protostars and Planets, Tucson, ed. Gehrels, T. Google Scholar
Goldreich, P., and Kwan, J.: 1974, Ap. J. 189, 441.Google Scholar
Goldsmith, P. F., and Langer, W. D.: 1978, Ap. J. in press.Google Scholar
Gordon, M. A., and Burton, W. B.: 1976, Ap. J. 208, 364.Google Scholar
Greisen, E. W.: 1973, Ap. J. 184, 379.Google Scholar
Greisen, E. W.: 1976, Ap. J. 203, 371.Google Scholar
Guélin, M., Langer, W. D., Snell, R. L., and Wootten, H. A.: 1977, Ap. J. (Letters) 217, L165.Google Scholar
Hartquist, T. W.: 1977, Ap. J. (Letters) 217, L45.Google Scholar
Harvey, P. M., Gatley, I., Werner, M. W., Elias, J. H., Evans, N. J., Zuckerman, B., Morris, G., Sato, T., and Litvak, M. M.: 1974, Ap. J. (Letters) 189, L87.Google Scholar
Heiles, C.: 1976, Ann. Rev. Astron. and Astrophys. 14, 1.CrossRefGoogle Scholar
Heiles, C., and Katz, G.: 1976, A. J. 81, 37.Google Scholar
Hopper, P. B., and Disney, M. J.: 1974, M.N.R.A.S. 168, 639.Google Scholar
Jenkins, E. B.: 1978a, Ap. J. 219, 845.Google Scholar
Jenkins, E. B.: 1978b, Ap. J. 220, 107.Google Scholar
Jura, M.: 1976, A. J. 81, 178.Google Scholar
Jura, M.: 1978, in Proc. of Conf. on Protostars and Planets, Tucson, ed. Behrels, T. Google Scholar
Knapp, G. R., and Jura, M.: 1976, Ap. J. 209, 782.Google Scholar
Knapp, G. R., Kuiper, T.B.H., Knapp, S. L., and Brown, R. L.: 1977, Ap. J. 214, 78.Google Scholar
Kutner, M. L., and Tucker, K. D.: 1975, Ap. J. 199, 79.Google Scholar
Kutner, M. L., Tucker, K. D., Chin, G. C., and Thaddeus, P.: 1977, Ap. J. 215, 736.CrossRefGoogle Scholar
Lada, C. J.: 1978, Conf. Proceedings of the Massive Molecular Clouds Workshop, Gregynog, Wales.Google Scholar
Lada, C. J., Elmegreen, B. G., Cong, H. I., and Thaddeus, P.: 1978, in preparation.Google Scholar
Langer, W. D.: 1978, preprint.Google Scholar
Larson, R. B.: 1978, preprint.Google Scholar
Lazareff, B.: 1975, Astron. and Astrophys. 42, 25.Google Scholar
Leung, C. M., and Liszt, H. S.: 1976, Ap. J. 208, 732.Google Scholar
Leung, C. M., and Brown, R. L.: 1977, Ap. J. (Letters) 214, L73.Google Scholar
Leung, C. M., and Liszt, H. S.: 1978, in preparation.Google Scholar
Loren, R. B.: 1977a, Ap. J. 215, 129.CrossRefGoogle Scholar
Loren, R. B.: 1977b, Ap. J. 218, 716.CrossRefGoogle Scholar
Martin, R. N., and Barrett, A. H.: 1978, Ap. J. Suppl. 36, 1.Google Scholar
McKee, C. F., and Ostriker, J. P.: 1977, Ap. J. 218, 148.CrossRefGoogle Scholar
Mezger, P. G.: 1977, in Star Formation, I.A.U. Symp. #75, ed. De Jong, T. and Maeder, A. (Reidel).CrossRefGoogle Scholar
Mouschovias, T. Ch.: 1976a, Ap. J. 206, 735.Google Scholar
Mouschovias, T. Ch.: 1976b, Ap. J. 207, 141.Google Scholar
Mufson, S. L., and Liszt, H. S.: 1977, Ap. J. 212, 664.Google Scholar
Myers, P. C.: 1977, Ap. J. 211, 737.CrossRefGoogle Scholar
Myers, P. C.: 1978, Ap. J., in press.Google Scholar
Sargent, A. I.: 1977, Ap. J. 218, 736.CrossRefGoogle Scholar
Savage, B. D., Bohlin, R. C., Drake, J. F., and Budich, W.: 1977, Ap. J. 216, 291.Google Scholar
Scoville, N. Z., and Solomon, P. M.: 1975, Ap. J. (Letters) 199, L105.Google Scholar
Scoville, N. Z., Solomon, P. M., and Penzias, A. A.: 1975, Ap. J. 201, 352.Google Scholar
Scoville, N. Z., and Solomon, P. M.: 1978, this volume.Google Scholar
Silk, J.: 1978, in Proc. of Conf. on Protostars and Planets, Tucson, ed. Gehrels, T. Google Scholar
Snell, R. N., and Loren, R. B.: 1977, Ap. J. 211, 122.Google Scholar
Spitzer, L.: 1978, Physical Processes in the Interstellar Medium, J. Wiley & Sons.Google Scholar
Spitzer, L., and Schwarzschild, M.: 1953, Ap. J. 118, 106.Google Scholar
Stark, A. A., and Blitz, L.: 1978, preprint.Google Scholar
Turner, B. E., and Zuckerman, B. 1978, Ap. J. (Letters), submitted.Google Scholar
Vrba, F. J., Strom, S. E., and Strom, K. M. 1976, A. J. 81, 958.Google Scholar
Vrba, F. J. 1977, in Star Formation, I.A.U. Symp. #75, ed. De Jong, T. and Maeder, A. (Reidel), pp. 243–245.Google Scholar
Werner, M. W., Elias, J. H., Gezari, D. Y., and Westbrook, W. E. 1974, Ap. J. (Letters) 192, L31.CrossRefGoogle Scholar
Wootten, A., Evans, N. J., Snell, R. N., and vanden Bout, P. 1978, Ap. J. submitted.Google Scholar