Astrophysics and Space Science

, Volume 4, Issue 1, pp 64–83 | Cite as

Correlation between the densities of X-ray sources and interstellar gas

  • M. Fujimoto
  • S. Hayakawa
  • T. Kato


The distribution of X-ray sources in our galaxy is obtained, assuming that the absolute X-ray luminosities of these sources are the same. The distribution is found to be in good correlation with the distribution of interstellar gas. The density of X-ray sources is nearly proportional to the square density of gas. This indicates that X-ray sources are comparatively young. The relation between the densities of X-ray sources and gas allows us to estimate the X-ray intensities of various objects such as Magellanic Clouds and Andromeda nebula, and also to obtain the average X-ray luminosity of spiral galaxies. The latter should increase as the age of a galaxy decreases, since the amount of gas decreases as the galaxy evolves. Under the assumptions that the gas density is inversely proportional to the age and that galaxies older thant0/30 are visible in X-rays, wheret0 is the present age of the universe, the contribution of X-ray sources in distant galaxies to the background component is calculated. The intensity and the spectrum of the background component of X-rays thus obtained are in fair agreement with observed ones in the energy range between 1 and 4 keV but significantly deviate from the latter at high energies.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Allen, C. W.: 1963,Astrophysical Quantities, The Athlone Press, London.Google Scholar
  2. Balasubrahmanyan, V. K., Boldt, E., Palmeira, R. A. R., andSandri, G.: 1968,Can. J. Phys. 46, S633.Google Scholar
  3. Barbanis, B. andWoltjer, L.: 1967,Astrophys. J. 150, 2, 461.Google Scholar
  4. Bleeker, J. A. M., Burger, J. J., Deerenberg, A. J. M., Scheepmaker, A., Swanenburg, B. N., Tanaka, Y., Hayakawa, S., Makino, F., andOgawa, H.: 1968,Can. J. Phys. 46, S461.Google Scholar
  5. Bowyer, C. S., Field, G. B., andMack, J. E.: 1968,Nature 217, 32.Google Scholar
  6. Bradt, H., Naranan, S., Rappaport, S., andSpada, G.: 1968, preprint.Google Scholar
  7. Braes, L. L. E. andHovenier, J. W.: 1966,Nature 209, 360.Google Scholar
  8. Ezek, D. andCameron, A. G. W.: 1967,Can. J. Phys. 45, 3429.Google Scholar
  9. Friedman, H., Byram, E. T., andChubb, T. A.: 1967,Science 156, 378.Google Scholar
  10. Fujimoto, M.: 1968,Astrophys. J. 152, 391.Google Scholar
  11. Green, D. W., Wilson, B. G., andBaxter, A. J.: 1968,Symposium on Small Rocket Instrumentations, COSPAR, Tokyo.Google Scholar
  12. Gursky, H., Gorenstein, P., andGiacconi, R.: 1967,Astrophys. J. 150, L75.Google Scholar
  13. Hayakawa, S. andMatsuoka, M.: 1964,Prog. Theor. Phys. Suppl. No. 30, 204.Google Scholar
  14. Hayakawa, S., Matsuoka, M., andSugimoto, D.: 1966,Space Sci. Rev. 5, 109.Google Scholar
  15. Hayakawa, S. andSugimoto, D.: 1968,Astrophys. Space Sci. 1, 216.Google Scholar
  16. Henry, R. C., Fritz, G., Meekins, J. F., Friedman, H., andByram, E. T.: 1968,Astrophys. J. 153, L11.Google Scholar
  17. Holmberg, E.: 1964,Arkiv Astron. 3, 387.Google Scholar
  18. Kerr, F. J.: 1962,Monthly Notices Roy. Astron. Soc. 123, 327.Google Scholar
  19. Lin, C. C. andShu, F. H.: 1964,Astrophys. J. 140, 646.Google Scholar
  20. Mandelštam, S. L. andTindo, I. P.: 1967,Soviet Phys. JETP. Letters 6, 796.Google Scholar
  21. Matsuoka, M., Oda, M., Ogawara, Y., Hayakawa, S., andKato, T.: 1969,Astrophys. Space Sci. 4, 44.Google Scholar
  22. Oda, M.: 1968,Space Sci. Rev. 8, 507.Google Scholar
  23. Peebles, P. J. E.: 1965,Astrophys. J. 142, 1317.Google Scholar
  24. Roberts, M.: 1963,Ann. Rev. Astron. Astrophys. 1, 149.Google Scholar
  25. Sato, H.: 1968,Prog. Theor. Phys. 40, 781.Google Scholar
  26. Schmidt, M.: 1959,Astrophys. J. 129, 243.Google Scholar
  27. Schmidt, M.: 1961, inProblems of Extra-Galactic Research (ed. by G. C. McVittie), MacMillan, New York.Google Scholar
  28. Sevard, F. D., Chodil, G., Mark, H., Swift, C. D., andToor, A.: 1967,Astrophys. J. 150, 845.Google Scholar
  29. Silk, J.: 1968,Astrophys. J. 151, L19.Google Scholar
  30. Sofue, Y.: 1968, to be submitted toPubl. Astron. Soc. Japan.Google Scholar
  31. Takase, B. andKinoshita, H.: 1967,Publ. Astron. Soc. Japan,19, 409.Google Scholar
  32. Tinsley, B. M.: 1968,Astrophys. J. 151, 547.Google Scholar
  33. Wallerstein, G.: 1967,Astrophys. Letters 1, 31.Google Scholar
  34. Westerhout, G.: 1962,IAU Symposium 15, 70.Google Scholar
  35. Wilson, B. G.: 1968,Rept. Inst. Space Aeronaut. Sci., Univ. of Tokyo,33, 289.Google Scholar

Copyright information

© D. Reidel Publishing Company, Dordrecht-Holland 1969

Authors and Affiliations

  • M. Fujimoto
    • 1
  • S. Hayakawa
    • 1
  • T. Kato
    • 1
  1. 1.Dept. of PhysicsNagoya UniversityNagoyaJapan

Personalised recommendations