Hostname: page-component-586b7cd67f-vdxz6 Total loading time: 0 Render date: 2024-11-27T11:08:15.560Z Has data issue: false hasContentIssue false
  • English
  • Français

The Vertical Structure of Warm Ionised Gas in the Milky Way

Published online by Cambridge University Press:  05 March 2013

B. M. Gaensler ,
G. J. Madsen ,
S. Chatterjee  and
S. A. Mao
B. M. Gaensler*
Affiliation:
Institute of Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
G. J. Madsen
Affiliation:
Institute of Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia Department of Astronomy, University of Wisconsin, Madison, WI 53706, USA
S. Chatterjee
Affiliation:
Institute of Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
S. A. Mao
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
*
DCorresponding author. Email: [email protected]
Rights & Permissions [Opens in a new window]

Abstract

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.

We present a new joint analysis of pulsar dispersion measures and diffuse Hα emission in the Milky Way, which we use to derive the density, pressure and filling factor of the thick disk component of the warm ionised medium (WIM) as a function of height above the Galactic disk. By excluding sightlines at low Galactic latitude that are contaminated by Hii regions and spiral arms, we find that the exponential scale-height of free electrons in the diffuse WIM is 1830–250+120 pc, a factor of two larger than has been derived in previous studies. The corresponding inconsistent scale heights for dispersion measure and emission measure imply that the vertical profiles of mass and pressure in the WIM are decoupled, and that the filling factor of WIM clouds is a geometric response to the competing environmental influences of thermal and non-thermal processes. Extrapolating the properties of the thick-disk WIM to mid-plane, we infer a volume-averaged electron density 0.014 ± 0.001 cm−3, produced by clouds of typical electron density 0.34 ± 0.06 cm−3 with a volume filling factor 0.04 ± 0.01. As one moves off the plane, the filling factor increases to a maximum of ∼30% at a height of ≈1–1.5 kpc, before then declining to accommodate the increasing presence of hot, coronal gas. Since models for the WIM with a ≈1 kpc scale-height have been widely used to estimate distances to radio pulsars, our revised parameters suggest that the distances to many high-latitude pulsars have been substantially underestimated.

Keywords

galaxies: ISMGalaxy: halo, structureglobular clusters: generalISM: structurepulsars: general
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 25 , Issue 4 , 2008 , pp. 184 - 200
Copyright
Copyright © Astronomical Society of Australia 2008

References

Alves, D. R., 2004, NewAR, 48, 659 CrossRefGoogle Scholar
Anantharamaiah, K. R., 1986, JApA, 7, 131 Google Scholar
Anderson, S. B., 1993, PhD thesis, California Institute of Technology Google Scholar
Backer, D. C., 1974, ApJ, 190, 667 CrossRefGoogle Scholar
Berkhuijsen, E. M., 1998, in IAUC 166: The Local Bubble and Beyond, Eds. Breitschwerdt, D., Freyberg, M. J. & Trümper, J. (Springer-Verlag), 301 Google Scholar
Berkhuijsen, E. M. & Müller, P., 2008, A&A, in press (arXiv:0807.3686)Google Scholar
Berkhuijsen, E. M., Mitra, D. & Müller, P., 2006, AN, 327, 82 (BMM06)Google Scholar
Bhattacharya, D. & Verbunt, F., 1991, A&A, 242, 128 Google Scholar
Biggs, J. D. & Lyne, A. G., 1996, MNRAS, 282, 691 CrossRefGoogle Scholar
Bland-Hawthorn, J., Sutherland, R., Agertz, O. & Moore, B., 2007, ApJ, 670, L109 CrossRefGoogle Scholar
Boulares, A. & Cox, D. P., 1990, ApJ, 365, 544 CrossRefGoogle Scholar
Bregman, J. N. & Lloyd-Davies, E. J., 2007, ApJ, 669, 990 CrossRefGoogle Scholar
Camilo, F., Lorimer, D. R., Freire, P., Lyne, A. G & Manchester, R. N., 2000, ApJ, 535, 975 CrossRefGoogle Scholar
Cecil, G., Bland-Hawthorn, J., Veilleux, S. & Filippenko, A. V., 2001, ApJ, 555, 338 CrossRefGoogle Scholar
Cordes, J. M. & Lazio, T. J. W., 2002, preprint (arXiv:0207156)Google Scholar
Cordes, J. M. & Lazio, T. J. W., 2003, preprint (arXiv:0301598)Google Scholar
Cordes, J. M., Weisberg, J. M., Frail, D. A., Spangler, S. R. & Ryan, M., 1991, Nature, 354, 121 CrossRefGoogle Scholar
Cowie, L. L. & McKee, C. F., 1977, ApJ, 211, 135 CrossRefGoogle Scholar
Cox, D. P., 2005, ARA&A, 43, 337 Google Scholar
Cox, D. P. & Reynolds, R. J., 1987, ARA&A, 25, 303 Google Scholar
Crawford, F., Kaspi, V. M., Manchester, R. N., Lyne, A. G., Camilo, F. & D'Amico, N., 2001, ApJ, 553, 367 CrossRefGoogle Scholar
de Avillez, M. A., 2000, MNRAS, 315, 479 CrossRefGoogle Scholar
Desai, K. M., Gwinn, C. R., Reynolds, J., King, E. A., Jauncey, D., Flanagan, C., Nicolson, G., Preston, R. A. & Jones, D. L., 1992, ApJ, 393, L75 CrossRefGoogle Scholar
Dettmar, R.-J., 2004, Ap&SS, 289, 349 Google Scholar
Efron, B. & Tibshirani, R. J., 1993, An Introduction to the Bootstrap (New York: Chapman & Hall)CrossRefGoogle Scholar
Everett, J. E., Zweibel, E. G., Benjamin, R. A., McCammon, D., Rocks, L. & Gallagher, J. S. III, 2008, ApJ, 674, 258 CrossRefGoogle Scholar
Ferguson, A. M. N., Wyse, R. F. G. & Gallagher, J. S., 1996, AJ, 112, 2567 CrossRefGoogle Scholar
Ferrière, K., 1998a, ApJ, 497, 759 CrossRefGoogle Scholar
Ferrière, K., 1998b, ApJ, 530, 700 CrossRefGoogle Scholar
Ferrière, K. M., 2001, RvMP, 73, 1031 Google Scholar
Ferguson, A. M. N., Wyse, R. F. G. & Gallagher, J. S., 1998, ApJ, 503, 700 Google Scholar
Finkbeiner, D. P., 2003, ApJS, 146, 407 CrossRefGoogle Scholar
Fletcher, A., Berkhuijsen, E. M., Beck, R. & Shukurov, A., 2004, A&A, 414, 53 Google Scholar
Fox, A. J., Wakker, B. P., Savage, B. D., Tripp, T. M. & Bland-Hawthorn, J., 2005, ApJ, 630, 332 CrossRefGoogle Scholar
Frail, D. A. & Weisberg, J. M., 1990, AJ, 100, 743 CrossRefGoogle Scholar
Freire, P. C., Kramer, M., Lyne, A. G., Camilo, F., Manchester, R. N. & D'Amico, N., 2001, ApJ, 557, L105 CrossRefGoogle Scholar
Gaensler, B. M., Haverkorn, M., Staveley-Smith, L., Dickey, J. M., McClure-Griffiths, N. M., Dickel, J. R. & Wolleben, M., 2005, Sci, 307, 1610 CrossRefGoogle Scholar
Gómez, G. C., Benjamin, R. A. & Cox, D. P., 2001, AJ, 122, 908 Google Scholar
Gould, R. J., 1971, Ap&SS, 10, 265 Google Scholar
Gratton, R. G., Bragaglia, A., Carretta, E., Clementini, G., Desidera, S., Grundahl, F. & Lucatello, S., 2003, A&A, 408, 529 Google Scholar
Haffner, L. M., Reynolds, R. J. & Tufte, S. L., 1999, ApJ, 523, 223 CrossRefGoogle Scholar
Haffner, L. M., Reynolds, R. J., Tufte, S. L., Madsen, G. J., Jaehnig, K. P. & Percival, J. W., 2003, ApJS, 149, 405 CrossRefGoogle Scholar
Harris, W. E., 1996, AJ, 112, 1487 CrossRefGoogle Scholar
Heiles, C., 2001, in Tetons 4: Galactic Structure, Stars and the Interstellar Medium, Eds. Woodward, C. E., Bicay, M. D. & Shull, J. M. (San Francisco: ASP), 231, 294 Google Scholar
Heiles, C., Koo, B.-C., Levenson, N. A. & Reach, W. T., 1996a, ApJ, 462, 326 CrossRefGoogle Scholar
Heiles, C., Reach, W. T. & Koo, B.-C., 1996b, ApJ, 466, 191 CrossRefGoogle Scholar
Hessels, J. W. T., Ransom, S. M., Stairs, I. H., Kaspi, V. M. & Freire, P. C. C., 2007, ApJ, 670, 363 CrossRefGoogle Scholar
Hill, A. S., Benjamin, R. A., Reynolds, R. J. & Haffner, L. M., 2005, BAAS, 37, 1302 Google Scholar
Hill, A. S., Benjamin, R. A., Kowal, G., Reynolds, R. J., Haffner, L. M. & Lazarian, A., 2008, ApJ, in press (arXiv: 0805.0155)Google Scholar
Hobbs, G., Lorimer, D. R., Lyne, A. G. & Kramer, M., 2005, MNRAS, 360, 974 CrossRefGoogle Scholar
Howk, J. C., Sembach, K. R. & Savage, B. D., 2003, ApJ, 586, 249 CrossRefGoogle Scholar
Howk, J. C., Sembach, K. R. & Savage, B. D., 2006, ApJ, 637, 333 CrossRefGoogle Scholar
Johnston, S., Koribalski, B., Weisberg, J. M. & Wilson, W., 2001, MNRAS, 322, 715 CrossRefGoogle Scholar
Korpi, M. J., Brandenburg, A., Shukurov, A., Tuominen, I. & Nordlund, A., 1999, ApJ, 514, L99 CrossRefGoogle Scholar
Kramer, M. et al., 2003, MNRAS, 342, 1299 CrossRefGoogle Scholar
Kulkarni, S. R. & Heiles, C., 1987, in Interstellar Processes, Eds. Hollenbach, D. J. & Thronson, H. A. (Kluwer), 87 CrossRefGoogle Scholar
Kulkarni, S. R. & Heiles, C. E., 1988, in Galactic and Extragalactic Radio Astronomy, Eds. Verschuur, G. L. & Kellermann, K. I. (Springer-Verlag), 95 CrossRefGoogle Scholar
Lazio, T. J. W. & Cordes, J. M., 1998a, ApJS, 115, 225 CrossRefGoogle Scholar
Lazio, T. J. W. & Cordes, J. M., 1998b, ApJ, 497, 238 CrossRefGoogle Scholar
Lorimer, D. R. et al., 2006, MNRAS, 372, 777 CrossRefGoogle Scholar
Lyne, A. G., Manchester, R. N. & Taylor, J. H., 1985, MNRAS, 213, 613 CrossRefGoogle Scholar
Madsen, G. J., Reynolds, R. J. & Haffner, L. M., 2006, ApJ, 652, 401 CrossRefGoogle Scholar
Manchester, R. N., Lyne, A. G., D'Amico, N., Bailes, M., Johnston, S., Lorimer, D. R., Harrison, P. A., Nicastro, L. & Bell, J. F., 1996, MNRAS, 279, 1235 CrossRefGoogle Scholar
Manchester, R. N., Hobbs, G. B., Teoh, A. & Hobbs, M., 2005, AJ, 129, 1993 CrossRefGoogle Scholar
Manchester, R. N., Fan, G., Lyne, A. G., Kaspi, V. M. & Crawford, F., 2006, ApJ, 649, 235 CrossRefGoogle Scholar
Mao, S. A., Gaensler, B. M., Stanimirović, S., Haverkorn, M., McClure-Griffiths, N. M., Staveley-Smith, L. & Dickey, J. M., 2008, ApJ, 686, in press (arXiv:0807.1532)Google Scholar
Miller, W. W. III & Cox, D. P., 1993, ApJ, 417, 579 CrossRefGoogle Scholar
Miller, S. T. & Veilleux, S., 2003, ApJS, 148, 383 CrossRefGoogle Scholar
Nordgren, T. E., Cordes, J. M. & Terzian, Y., 1992, AJ, 104, 1465 CrossRefGoogle Scholar
Peterson, J. D. & Webber, W. B., 2002, ApJ, 575, 217 Google Scholar
Press, W. H., Teukolsky, S. A., Vetterling, W. T. & Flannery, B. P., 1992, Numerical Recipes: The Art of Scientific Computing (2nd edition: Cambridge: Cambridge University Press)Google Scholar
Pynzar', A. V., 1993, ARep, 37, 245 Google Scholar
Rand, R. J., 1998, PASA, 15, 106 CrossRefGoogle Scholar
Rand, R. J., Kulkarni, S. R. & Hester, J. J., 1990, ApJ, 352, L1 CrossRefGoogle Scholar
Ransom, S. M., 2007, in ASPC 365, SINS – Small Ionized and Neutral Structures in the Diffuse Interstellar Medium, Eds. Haverkorn, M. & Goss, W. M., 265 Google Scholar
Readhead, A. C. S. & Duffett-Smith, P. J., 1975, A&A, 42, 151 Google Scholar
Reynolds, R. J., 1977, ApJ, 216, 433 CrossRefGoogle Scholar
Reynolds, R. J., 1980, ApJ, 236, 153 CrossRefGoogle Scholar
Reynolds, R. J., 1983, ApJ, 268, 698 CrossRefGoogle Scholar
Reynolds, R. J., 1984, ApJ, 282, 191 CrossRefGoogle Scholar
Reynolds, R. J., 1989, ApJ, 339, L29 CrossRefGoogle Scholar
Reynolds, R. J., 1990a, in IAUS 139, The galactic and extragalactic background radiation, Eds. Bowyer, S. & Leinert, C. (Dordrecht: Kluwer Academic), 157 CrossRefGoogle Scholar
Reynolds, R. J., 1990b, ApJ, 349, L17 CrossRefGoogle Scholar
Reynolds, R. J., 1990c, ApJ, 348, 153 CrossRefGoogle Scholar
Reynolds, R. J., 1991a, ApJ, 372, L17 CrossRefGoogle Scholar
Reynolds, R. J., 1991b, in IAUS 144, The interstellar disk-halo connection in galaxies, Ed. Bloemen, H. (Dordrecht: Kluwer Academic), 67 CrossRefGoogle Scholar
Reynolds, R. J., 1997, in The Physics of Galactic Halos, Eds. Lesch, H., Dettmar, R.-J., Mebold, U. & Schlickeiser, R. (Berlin: Akademie Verlag), 57 Google Scholar
Reynolds, R. J. & Tufte, S. L., 1995, ApJ, 439, L17 CrossRefGoogle Scholar
Reynolds, R. J., Tufte, S. L., Kung, D. T., McCullough, P. R. & Heiles, C., 1995, ApJ, 448, 715 CrossRefGoogle Scholar
Reynolds, R. J., Haffner, L. M. & Tufte, S. L., 1999, ApJ, 525, L21 CrossRefGoogle Scholar
Roshi, D. A. & Anantharamaiah, K. R., 2001, ApJ, 557, 226 CrossRefGoogle Scholar
Savage, B. D., Edgar, R. J. & Diplas, A., 1990, ApJ, 361, 107 CrossRefGoogle Scholar
Schlegel, D. J., Finkbeiner, D. P. & Davis, M., 1998, ApJ, 500, 525 CrossRefGoogle Scholar
Sembach, K. R., Wakker, B. P., Savage, B. D., Richter, P., Meade, M., Shull, J. M., Jenkins, E. B., Sonneborn, G. & Moos, H. W., 2003, ApJS, 146, 165 CrossRefGoogle Scholar
Sfeir, D. M., Lallement, R., Crifo, F. & Welsh, B. Y., 1999, A&A, 346, 785 Google Scholar
Shishov, V. I. & Smirnova, T. V., 2002, ARep, 46, 731 Google Scholar
Shull, J. M. & Slavin, J. D., 1994, ApJ, 427, 784 CrossRefGoogle Scholar
Sternberg, A., McKee, C. F. & Wolfire, M. G., 2002, ApJS, 143, 419 CrossRefGoogle Scholar
Story, S. A., Gonthier, P. L. & Harding, A. K., 2007, ApJ, 671, 713 CrossRefGoogle Scholar
Sun, X.-H., Han, J.-L. & Qiao, G.-J., 2002, Chin. J. Astron. Astrophys., 2, 133 CrossRefGoogle Scholar
Sun, X. H., Reich, W., Waelkens, A. & Enßlin, T. A., 2008, A&A, 477, 573 Google Scholar
Taylor, J. H. & Cordes, J. M., 1993, ApJ, 411, 674 CrossRefGoogle Scholar
Toscano, M., Britton, M. C., Manchester, R. N., Bailes, M., Sandhu, J. S., Kulkarni, S. R. & Anderson, S. B., 1999, ApJ, 523, L171 CrossRefGoogle Scholar
Vieser, W. & Hensler, G., 2007, A&A, 475, 251 Google Scholar
Walker, A. R., 2003, in Stellar Candles for the Extragalactic Distance Scale, Eds. Alloin, D. & Gieren, W. (Berlin: Springer-Verlag), 265 CrossRefGoogle Scholar
Weisberg, J. M., Stanimirović, S., Xilouris, K., Hedden, A., de la Fuente, A., Anderson, S. B. & Jenet, F. A., 2008, ApJ, 674, 286 CrossRefGoogle Scholar
Wolfire, M. G., McKee, C. F., Hollenbach, D. & Tielens, A. G. G. M., 1995, ApJ, 453, 673 CrossRefGoogle Scholar
Xu, Y., Reid, M. J., Zheng, X. W. & Menten, K. M., 2006, Sci, 311, 54 CrossRefGoogle Scholar
Yao, Y. & Wang, Q. D., 2005, ApJ, 624, 751 CrossRefGoogle Scholar