Journal of Astrophysics and Astronomy

, Volume 3, Issue 4, pp 399–412 | Cite as

Interstellar electron density

  • M. Vivekanand
  • R. Narayan


We impose the requirement that the spatial distribution of pulsars deduced from their dispersion measures using a model of the galactic electron density (n e ) should be consistent with cylindrical symmetry around the galactic centre (assumed to be 10 kpc from the Sun). Using a carefully selected subsample of the pulsars detected by the II Molonglo Survey (II MS), we test a number of simple models and conclude that (i) the effective mean 〈ne〉) for the whole galaxy is 0.037-0.012 +0.020 cm-3, (ii) the scale height of electrons is greater than 300 pc and probably about 1 kpc or more, and (iii) there is little evidence for variation of ne with galactic radius RGC for RGc ≳ 5 kpc. Further, we make a detailed analysis of the contribution to ne from H II regions. Combining the results of a number of relatively independent calculations, we propose a model for the galactic electron density of the formn e (z) = 0.030 + 0.020 exp (- |z|/70) cm-3 where z(pc) is the height above the galactic plane and the second term describes the contribution from H II regions. We believe the statistical uncertainties in the parameters of this model are quite small.

Key words

pulsars dispersion measure-interstellar electron density H II regions 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Ables, J. G., Manchester, R. N. 1976,Astr. Astrophys.,50, 177.ADSGoogle Scholar
  2. Arnett, W. D., Lerche, I. 1981,Astr. Astrophys.,95, 308.ADSMathSciNetGoogle Scholar
  3. Crovisier, J. 1978,Astro, Astrophys.,70, 43.ADSGoogle Scholar
  4. del Romero, A., Gomez-Gonzalez, J. 1981,Astr. Astrophys.,104, 83.ADSGoogle Scholar
  5. Hall, A. N. 1980,Mon. Not. Rastr. Soc.,191, 751.ADSGoogle Scholar
  6. Harding, D. S., Harding, A. K. 1982,Astrophys. J.,257, 603.CrossRefADSGoogle Scholar
  7. Lyne, A. G. 1980, inIAU Symp. 95: Pulsars, Eds W. Sieber and R. Weilebinski, D. Reidel, Dordrecht, p. 413.Google Scholar
  8. Mancheser, R. N., Lyne, A G., Taylor, J. H., Durdin, J. M., Large, M. I., Little, A. G. 1978,Mon. Not. R. astr. Soc.,185, 409.ADSGoogle Scholar
  9. Manchester, R. N., Taylor, J. H. 1977,Pulsars, Freeman, San Francisco.Google Scholar
  10. Manchester, R. N., Taylor, J. H. 1981,Astr. J.,86, 1953.CrossRefADSGoogle Scholar
  11. McKee, C. F., Ostriker, J. P. 1977,Astrophys. J.,218, 148.CrossRefADSGoogle Scholar
  12. Oort, J. H. 1977,A. Rev. Astr. Astrophys.,15, 295.CrossRefADSGoogle Scholar
  13. Prentice, A. J. R., ter Haar, D. 1969,Mon. Not. R. astr. Soc.,146, 423.ADSGoogle Scholar
  14. Taylor, J. H., Manchester, R. N. 1977,Astrophys. J.,215, 885.CrossRefADSGoogle Scholar
  15. Vivekanand, M., Narayan, R., Radhakrishnan, V. 1982,J. Astrophys. Astr.,3, 237.ADSGoogle Scholar

Copyright information

© Indian Academy of Sciences 1982

Authors and Affiliations

  • M. Vivekanand
    • 1
  • R. Narayan
    • 1
  1. 1.Raman Research InstituteBangalore

Personalised recommendations