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The Galactic Electron Density Distribution

Published online by Cambridge University Press:  12 April 2016

Joel M. Weisberg*
Affiliation:
Department of Physics and Astronomy, Carleton College, Northfield, MN, USA

Abstract

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Pulsars are excellent probes of the galactic free electron layer. Interstellar dispersion and scattering measurably affect the observed pulsar signals, thereby providing information on the distribution and density of the free electrons causing these phenomena.

Primary calibration of galactic electron density models is achieved through adjusting their parameters to fit the observed dispersion of pulsars having independently measured distances. The distances are determined via kinematic analyses of HI absorption spectra, through angular or timing parallax measurements, and from associations with other objects of known distances.

The models have become steadily more refined as the body of data upon which they are based has grown. Independent distance measurements continue to accrue. The discovery of pulsars in globular clusters provided high latitude lines of sight for probing the z-distribution (Reynolds 1989). Additional calibration has been provided through incorporation of interstellar scattering measurements into the modelling process (Cordes et al. 1991). Individual spiral arms are now explicitly modelled (Taylor & Cordes 1993).

While great progress has been achieved with these models, there are still uncertainties in modelling the electron density of the local region and the inner Galaxy, and in the z–distribution of the electron layer. Currently anticipated observations will help to resolve some of these issues.

Type
Part 6 Winds and the ISM
Copyright
Copyright © Astronomical Society of the Pacific 1996

References

Ables, J.G., Manchester, R.N. 1976, A&A, 50, 177 Google Scholar
Bailes, M., Manchester, R.N., Kesteven, M.J., Norris, R.P., Reynolds, J.E. 1990, Nature, 343,240 Google Scholar
Bell, J.F., Bailes, M. 1996a, ApJL, 456, L33 Google Scholar
Bhattacharya, D., Verbunt, F. 1991, A&A, 242, 128 Google Scholar
Camilo, F., Foster, R.S., Wolszczan, A. 1994, ApJL, 437, L39 Google Scholar
Camilo, F., Nice, D.J. 1995, ApJ, 445, 756 Google Scholar
Cordes, J.M., Weisberg, J.M., Frail, D.A., Spangler, S.R., Ryan, M. 1991, Nature, 354, 121 Google Scholar
Cox, D.P., Reynolds, R.J. 1987, ARA&A, 25, 303 Google Scholar
Fich, M., Blitz, L., Stark, A.A. 1989, ApJ, 342, 272 Google Scholar
Foster, R.S., Cadwell, B.J., Wolszczan, A., Anderson, S.B. 1995, ApJ, 454, 826 Google Scholar
Frail, D.A., Cordes, J.M., Hankins, T.H., Weisberg, J.M. 1991, ApJ, 382, 168 Google Scholar
Frail, D.A., Goss, W.M., Whiteoak, J.B.Z. 1994, ApJ 437, 781 Google Scholar
Frail, D.A., Kulkarni, S.R., Vasisht, G. 1993, Nature, 365, 136 Google Scholar
Frail, D.A., Weisberg, J.M. 1990, AJ, 100, 743 Google Scholar
Frisch, P.C. 1994, Science, 265, 1423 Google Scholar
Gaensler, B.M., Johnston, S. 1995, MNRAS, 277, 1243 Google Scholar
Georgelin, Y.M., Georgelin, Y.P. 1976, A&A, 49, 57 Google Scholar
Gorham, P.W., Ray, P.S., Anderson, S.B., Kulkarni, S.R., Prince, T.A. 1996, ApJ, 458, 257 Google Scholar
Gupta, Y. 1995, ApJ, 451, 717 CrossRefGoogle Scholar
Gwinn, C.R., Taylor, J.H., Weisberg, J.M., Rawley, L.A. 1986, AJ, 91, 338 CrossRefGoogle Scholar
Hurwitz, M., Bowyer, S. 1995, ApJ, 446, 812 Google Scholar
Johnston, S., Koribalski, B., Weisberg, J.M., Wilson, W. 1996, MNRAS, 279, 661 Google Scholar
Kaspi, V.M., Taylor, J.H., Ryba, M.F. 1994, ApJ, 428, 713 Google Scholar
Kerr, F.J. Lynden-Bell, D. 1986, MNRAS, 221, 1023 Google Scholar
Kopeikin, S.M. 1995, ApJL, 439, L5 Google Scholar
Koribalski, B., Johnston, S., Weisberg, J.M., Wilson, W. 1995, ApJ, 441,756 Google Scholar
Lallement, R., Bertin, P., Ferlet, R., Vidal-Madjar, A., Bertaus, J.L. 1994, A&A, 286, 898 Google Scholar
Large, M.I., Vaughan, A.E., Mills, B.Y. 1968, Nature, 220, 340 Google Scholar
Lyne, A.G., Manchester, R.N., & Taylor, J.H. 1985, MNRAS, 213, 613 Google Scholar
Manchester, R.N., Lyne, A.G., D’Amico, N., Bailes, M., Johnston, S., Lorimer, D., Harrison, P.A., Nicastro, L., Bell, J. 1996, MNRAS, in pressGoogle Scholar
Nordgren, T.K., Cordes, J.M., Terzian, Y. 1992, AJ, 104, 1465 Google Scholar
Reynolds, R.J. 1989, ApJL, 389, L29 CrossRefGoogle Scholar
Ryba, M.F., Taylor, J.H. 1991, ApJ, 371, 739 CrossRefGoogle Scholar
Schmidt, M. 1965, in Galactic Structure, ed. Blaauw, A. and Schmidt, M., Chicago: Univ. Chicago Press, p. 513 Google Scholar
Staelin, D.H., Reifenstein, E.C. III 1968, Science, 162, 1481 Google Scholar
Taylor, J.H., Cordes, J.M. 1993, ApJ, 411, 674 Google Scholar
Taylor, J.H., Manchester, R.N., ApJ, 215, 885 Google Scholar
Taylor, J.H., Manchester, R.N., Lyne, A.G. 1993, ApJS, 88, 529 CrossRefGoogle Scholar
Vivekanand, M., Narayan, R. 1982, J. Astrophys . Astr., 3, 399 Google Scholar
Weisberg, J.M., Boriakoff, V., Rankin, J. 1979, A&A, 77, 204 Google Scholar
Weisberg, J.M., Siegel, M.H., Frail, D.A., Johnston, S. 1995, ApJ, 447, 204 Google Scholar