Abstract
A recent survey of the fine-structure excitation of neutral carbon reveals that the interstellar medium in the Galactic plane exhibits a thermal pressure, nT/k, that ranges from about 103 to 104cm−3K from one location to the next, with occasional excursions in excess of about 105 cm−3 K. The large excitations for small amounts of gas indicate that some regions are either subjected to shocks or must be pressurized within time scales much shorter than the time needed to reach thermal equilibrium. These rapid fluctuations probably arise from the cascade of macroscopic mechanical energy to small scales through a turbulent cascade. One consequence of this effect is that changes in gas temperature can arise from near adiabatic compressions and expansions, and this may explain why investigations of 21-cm emission and absorption reveal the presence of hydrogen at temperatures well below the expected values derived from the balance of various known heating and cooling processes.
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Abbreviations
- ISM::
-
Interstellar Medium
References
Andrews, S.M., Meyer, D.M. and Lauroesch, J.T.: 2001, ApJ 552, L73–L76.
Ballesteros-Paredes, J., Vázquez-Semadeni, E. and Scalo, J.: 1999, ApJ 515, 286–303.
Begelman, M.C.: 1990, in: H. Thronson and M. Shull (eds.), The Interstellar Medium in Galaxies, Kluwer, Dordrecht, pp. 287–304.
Boulares, A. and Cox, D.P.: 1990, ApJ 365, 544–558.
Chandrasekhar, S. and Münch, G.: 1952, ApJ 115, 103–123.
Cox, D.P.: 1979, ApJ 234, 863–875.
Cox, D.P.: 1981, ApJ 245, 534–551.
Cox, D.: 1995, Nature 375, 185–186.
Cox, D.P. and Smith, B.W.: 1974, ApJ (Letters) 189, L105–L108.
Davis, R.J., Diamond, P.J. and Goss, W.M.: 1996, MNRAS 283, 1105–1114.
Diamond, P.J., Goss, W.M., Romney, J.D., Booth, R.S., Kalberla, P.M.W. and Mebold, U.: 1989, ApJ 347, 302–306.
Dickey, J.M., McClure-Griffiths, N.M., Gaensler, B.M. and Green, A.J.: 2003, ApJ 585, 801.
Dieter, N.H., Welch, W.J. and Romney, J.D.: 1976, ApJ (Letters) 206, LI 13–L115.
Faison, M.D. and Goss, W.M.: 2001, AJ 121, 2706–2722.
Faison, M.D., Goss, W.M., Diamond, P.J. and Taylor, G.B.: 1998, AJ 116, 2916–2928.
Field, G.B.: 1965, ApJ 142, 531–567.
Field, G.B., Goldsmith, D.W. and Habing, H.J.: 1969, ApJ (Letters) 155, L149–L154.
Frail, D.A., Weisberg, J.M., Cordes, J.M. and Mathers, C.: 1994, ApJ 436, 144–151.
Gazol, A., Vázquez-Semadeni, E., Sánchez-Salcedo, F.J. and Scalo, J.: 2001, ApJ 557, L121–L124.
Gibson, S.J., Taylor, A.R., Higgs, L.A. and Dewdney, P.E.: 2000, ApJ 540, 851–862.
Heiles, C.: 2001, ApJ (Letters) 551, L105–L108.
Heiles, C. and Troland, T.H.: 2003, ApJ 586, 1067.
Jenkins, E.B.: 2002, astro-ph, 0207579.
Jenkins, E.B., Jura, M. and Loewenstein, M.: 1983, ApJ 270, 88–104.
Jenkins, E.B. and Shaya, E.J.: 1979, ApJ 231, 55–72.
Jenkins, E.B. and Tripp, T.M.: 2001, ApJ (Suppl.) 137, 297–340.
Knee, L.B.G. and Brunt, CM.: 2001, Nature 412, 308–310.
Lauroesch, J.T., Meyer, D.M. and Blades, J.C.: 2000, ApJ 543, L43–L47.
MacLow, M.-M., Balsara, D., Avillez, M.A. and Kim, J.: 2001, astro-ph, 0106509.
McKee, C.F. and Ostriker, J.P.: 1977, ApJ 218, 148–169.
Meyer, D.M. and Lauroesch, J.T.: 1999, ApJ 520, L103–L106.
Shull, J.M.: 1987, in: D.J. Hollenbach and H.A. Thronson (eds.), Interstellar Processes, Reidel, Dordrecht, pp. 225–244.
Vázquez-Semadeni, E., Gazol, A. and Scalo, J.: 2000, ApJ 540, 271–285.
Weingartner, J.C. and Draine, B.T.: 2001, ApJ 563, 842–852.
Wolfire, M.G., Hollenbach, D., McKee, C.F., Tielens, A.G.G.M. and Bakes, E.L.O.: 1995, ApJ 443, 152–168.
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Jenkins, E.B. (2004). Evidence and Implications of Pressure Fluctuations in the ISM. In: de Avillez, M.A., Breitschwerdt, D. (eds) From Observations to Self-Consistent Modelling of the ISM in Galaxies. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-0979-9_6
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DOI: https://doi.org/10.1007/978-94-007-0979-9_6
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