Hostname: page-component-848d4c4894-mwx4w Total loading time: 0 Render date: 2024-06-19T17:04:09.308Z Has data issue: false hasContentIssue false
  • English
  • Français

The Extragalactic X-Ray and γ-ray Backgrounds

Published online by Cambridge University Press:  08 February 2017

G. Setti
G. Setti*
Affiliation:
European Southern Observatory Karl-Schwarzschild-Str. 2 D-0846 Garching bei München FRG

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.

The long-standing problem of the origin of the extragalactic X-ray background (XRB) is reviewed. Although the shape of the spectrum in the 3–100 keV interval is suggestive of an optically thin bremsstrahlung at ~ 40 keV, the interpretation in terms of a hot intergalactic gas (IGG) requires a rather extreme energy supply and a gas density conflicting with the baryon density upper limit derived from primordial nucleosynthesis calculations in the standard hot big-bang model. A summary discussion of the estimated contributions from the integrated X-ray emission of known classes of extragalactic discrete sources at a reference energy of 2 keV is given. Although these estimates are still uncertain, the subtraction of a “minimum” contribution drastically modifies the 40 keV thermal shape, which is the prima facie evidence of a hot IGG. AGNs are the main contributors. Low luminosity AGNs (Seyfert type 1 nuclei) at redshift z = 1 − 2 may in fact saturate the 2 keV XRB, but their observed hard X-ray spectra are on the average unlike (much too steep) that of the XRB. This has led a number of authors to postulate new classes of sources and some exotic models which are briefly summarized. However, if a recently proposed unified scheme of AGNs holds, then the bulk of the XRB intensity can be explained independently of the observed spectral differences and with a mild cosmological evolution. The origin of the extragalactic γ-ray background is briefly commented upon in the concluding remarks.

Type
IV. Extragalactic Background Radiation and Cosmology
Information
Symposium - International Astronomical Union , Volume 139: The Galactic and Extragalactic Background Radiation , 1990 , pp. 345 - 356
Copyright
Copyright © Kluwer 1990 

References

REFERENCES

Anderson, S. F., and Margon, B. 1987, Astrophys. J., 314, 111.CrossRefGoogle Scholar
Barcons, X. 1987, Astrophys. J., 313, 547.CrossRefGoogle Scholar
Barcons, X. 1989, in Proc. IAU 139, Galactic and Extragalactic Background Radiation, ed. Bowyer, S., and Leinert, Ch. (Dordrecht: Kluwer Academic Publishers).Google Scholar
Barcons, X., and Fabian, A. C. 1988, Mon. Not. R. astr. Soc., 230, 189.Google Scholar
Barcons, X., and Lapiedra, R. 1985, Astrophys. J., 289, 33.Google Scholar
Barthel, P. D. 1989, Astrophys. J., 336, 606.Google Scholar
Bignami, G. F., Fichtel, C. E., Hartmann, R. F., and Thompson, D. J. 1979, Astrophys. J., 232, 649.Google Scholar
Boesgaard, A. M., and Steigman, G. 1985, Ann. Rev. Astr. Astrophys., 23, 319.Google Scholar
Boldt, E. 1987, Phy. Reports, 146, No. 4, 215.CrossRefGoogle Scholar
Boldt, E. 1988, NASA Report #88-037.Google Scholar
Boldt, E., and Leiter, D. 1987, Astrophys. J., 322, L1.Google Scholar
Bookbinder, J., Cowie, L. L., Krolik, J. H., Ostriker, J. P., and Rees, M. J. 1980, Astrophys. J., 237, 647.Google Scholar
Canizares, C. R., and White, J. L. 1989, Astrophys. J., 339, 27.Google Scholar
Cheng, E. S., Saulson, P. R., Wilkinson, D. T., and Corey, B. E. 1979, Astrophys. J., 232, L139.Google Scholar
Cowsik, R., and Kobetich, E. J. 1972, Astrophys. J., 177, 585.Google Scholar
Daly, R. A. 1987, Astrophys. J., 322, 20.Google Scholar
Daly, R. A. 1989, paper presented at IAU Symposium 139, “Galactic and Extragalactic Background Radiation,” June 12–16, 1989, Heidelberg, Federal Republic of Germany.Google Scholar
Danese, L., De Zotti, G., Fasano, G., and Franceschini, A. 1986, Astrophys. J., 161, 1.Google Scholar
De Zotti, G., Boldt, E. A., Cavaliere, A., Danese, L., Franceschini, A., Marshall, F. E., Swank, J. H., and Szymkowiak, A. E. 1982, Astrophys. J., 253, 47.CrossRefGoogle Scholar
Fabian, A. C., Done, C., and Ghisellini, G. 1988, Mon. Not. R. astr. Soc., 232, 21P.Google Scholar
Fichtel, C. E., Simpson, G. A., and Thompson, D. J. 1978, Astrophys. J., 222, 833.CrossRefGoogle Scholar
Field, G. B., and Perrenod, S. C. 1977, Astrophys. J., 215, 717.Google Scholar
Fomalont, E. B., Kellerman, K. I., and Wall, J. V. 1984. Astrophys. J., 277, L23.CrossRefGoogle Scholar
Giacconi, R., Gursky, H., Paolini, F., and Rossi, B. 1962, Phys. Rev. Letters, 9, 439.Google Scholar
Giacconi, R., et al. 1979, Astrophys. J., 234, L1.CrossRefGoogle Scholar
Giacconi, R., and Zamorani, G. 1987. Astrophys. J., 313, 20.Google Scholar
Gioia, I. M., Maccacaro, T., Schild, R. E., Stocke, J. T., Liebert, J. W., Danziger, I. J., Kunth, D., and Lub, J. 1984, Astrophys. J., 283, 495.Google Scholar
Griffiths, R. E. 1989, NATO-ASI on “The Epoch of Galaxy Formation,” eds. Frenk, C. S. et al. (Kluwer, Dordrecht), 235.Google Scholar
Gruber, D. E., Rothschild, R. E., Matteson, J. L., and Kinzer, R. L. 1984, in X-Ray and UV Emission from Active Galactic Nuclei, eds. Brinkmann, W. and Trümper, J., MPE Report 184, 129.Google Scholar
Guilbert, P. W., and Fabian, A. C. 1986, Mon. Not. R. astr. Soc., 220, 439.CrossRefGoogle Scholar
Hamilton, T. T., and Helfand, D. J. 1987, Astrophys. J., 318, 93.CrossRefGoogle Scholar
Inoue, H. 1989, in Big Bang, Active Galactic Nuclei and Supernovae, Universal Ac. Press, Tokyo, 301.Google Scholar
Kinzer, R. L., Johnson, W. N., and Kurfers, J. D. 1978, Astrophys. J., 222, 370.Google Scholar
Knoke, J. E., Partridge, R. B., Ratner, M. I., and Shapiro, I.I. Astrophys. J., 284, 479.Google Scholar
Leiter, D., and Boldt, E. 1982, Astrophys. J., 260, 1.Google Scholar
Maccacaro, T., Gioia, I. M., Wolter, A., Zamorani, G., and Stocke, J. T. 1988, Astrophys. J., 326, 680.Google Scholar
Makishima, K., and Ohashi, T. 1989, in Big Bang, Active Galactic Nuclei and Supernovae, Universal Ac. Press, Tokyo, 371.Google Scholar
Marshall, F. E., Boldt, E. A., Holt, S. S., Miller, R. B., Mushotzky, R. F., Rose, L. A., Rothschild, R. E., and Serlemitsos, P. J. 1980, Astrophys. J., 235, 4.Google Scholar
Morisawa, K., and Takahara, F. 1989, P. A. S. J., to be published.Google Scholar
Mushotzky, R. F. 1984, in COSPAR/IAU Symposium, High-Energy Astrophysics and Cosmology , eds. Bignami, G. F. and Sunayev, R. A., Adv. Space Res., 3, 157.CrossRefGoogle Scholar
Ostriker, J. P., Thompson, C., and Witten, E. 1986, Phys. Letters, B180, 231.Google Scholar
Piccinotti, et al. 1982, Astrophys. J., 253, 485.CrossRefGoogle Scholar
Ramana Murthy, P. V., and Wolfendale, A. W. 1986, Gamma Ray Astronomy (Cambridge University Press, Cambridge).Google Scholar
Reeves, H., Richer, J., Sato, K, and Terasawa, N. 1989, preprint.Google Scholar
Schmidt, M., and Green, R. F. 1986, Astrophys. J., 305, 68.Google Scholar
Schönfelder, V. 1978, Nature, 274, 344.Google Scholar
Schönfelder, V., Grami, F., and Penningsfeld, F.-P. 1980, Astrophys. J., 240, 350.Google Scholar
Setti, G., and Woltjer, L. 1979, Astron. Astrophys., 76, L1.Google Scholar
Setti, G., and Woltjer, L. 1982, in Astrophysical Cosmology, eds. Bruck, H. A., Coyne, G. V., and Longair, M. S. (Pontificia Academia Scientiarum, Vatican City), 315.Google Scholar
Setti, G. 1984, in X-Ray and UV Emission from Active Galactic Nuclei, eds. Brinkmann, W. and Trümper, J., MPE Report 184, 243.Google Scholar
Setti, G. 1985, in Non-Thermal and Very High Temperature Phenomena in X-Ray Astronomy, eds. Perola, G. C. and Salvati, M. (Istituto Astronomico, Università “La Sapienza,” Rome), 159.Google Scholar
Setti, G. 1987, in IAU Symposium No. 124, Observational Cosmology, eds. Hewitt, A., Burbidge, G., and Fang, L. Z. (Reidel, Dordrecht), 579.Google Scholar
Setti, G., and Woltjer, L. 1989, submitted.Google Scholar
Shafer, R. A. 1983, NASA Tech. Mem. 85029. Google Scholar
Shafer, R. A., and Fabian, A. C. 1983, in IAU Symposium No. 104, Early Evolution of the Universe and Its Present Structure, eds Abell, G. O. and Chincarini, G. (Reidel, Dordrecht), 333.Google Scholar
Smoot, G. F., Gorenstein, M. V., and Muller, R. A. 1977, Phys. Rev. Letters, 39, 898.Google Scholar
Tananbaum, H., Avni, Y., Green, R. F., Schmidt, M., and Zamorani, G. 1986, Astrophys. J., 305, 57.Google Scholar
Taylor, G. B., and Wright, E. L. 1989, Astrophys. J., 339, 619.Google Scholar
Thompson, D. J., and Fichtel, C. E. 1982. Astron. Astrophys., 109, 352.Google Scholar
Trombka, J. I, Dyer, C. S., Evans, L. G., Bielefeld, M. J., Seltzer, S. M., and Metzger, A. E. 1977, Astrophys. J., 212, 925.Google Scholar
Turner, T. J., and Pounds, K. A. 1989. Mon. Not. R. astr. Soc., submitted.Google Scholar
Tyson, J. A. 1984, in IAU Colloquium 78, Astronomy with Schmidt Type Telescopes, ed. Capaccioli, M. (Reidel, Dordrecht), 489.Google Scholar
Wilkes, B. J., and Elvis, M. 1987, Astrophys. J., 323, 243.Google Scholar
Worrall, D. M., Mushotzky, R. F., Boldt, E. A., Holt, S. S., and Serlemitsos, P. J. 1979, Astrophys. J., 232, 683.Google Scholar
Zamorani, G., et al. 1981, Astrophys. J., 245, 357.Google Scholar