Abstract
Detailed information on the high-energy gamma-ray emission from our Galaxy has become available through the two dedicated satellite missions SAS-2 and COS-B. The consistency of the two datasets is discussed; while a satisfying general agreement is observed, a few distinct discrepancies point to possible time variations within the compact source component of the total galactic emission. The bulk of emission appears very well correlated to the column density of the total interstellar gas, as traced by radio observations of Hi and CO. The gamma-ray observations exclude the possibility that H2 dominates in the inner Galaxy, its mass should not exceed the mass existing in the form of Hi. Neither a significant galactocentric gradient of the (high-energy) cosmic-ray flux density is suggested inside the solar circle (outside a decrease is needed), nor a linear coupling between the cosmic rays and the gas is indicated by the gamma-ray data. The systematic variation with longitude of the spectrum of the gamma-ray emission points to an increased flux of cosmic-ray electrons in the 100 MeV to 1 GeV energy range in regions where dense clouds are concentrated. The variation could as well be due to the largely unresolved population of compact gamma-ray objects.
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Bignami, G. F., Boella, G., Burger, J. J., Keirle, P., Mayer-Hasselwander, H. A., Paul, J. A., Pfeffermann, E., Scarsi, L., Swanenburg, B. N., Taylor, B. G., Voges, W., and Wills, R. D.: 1975, Space Sci. Instr. 1, 245.
Blitz, L. and Shu, F. H.: 1980, Astrophys. J. 238, 148.
Buccheri, R., et al.: 1983, submitted to Astron. Astrophys.
Caraveo, P. A. and Paul, J. A.: 1979, Astron. Astrophys. 75, 340.
Caraveo, P. A., Bennett, K., Bignami, G. F., Hermsen, W., Kanbach, G., Lebrun, F., Masnou, J. L., Mayer-Hasselwander, H. A., Paul, J. A., Sacco, B., Scarsi, L., Strong, A. W., Swanenburg, B. N., and Wills, R. D.: 1980, Astron. Astrophys. 91, L3.
Cesarsky, C. J. and Völk, H. J.: 1978, Astron. Astrophys. 70, 367.
Cohen, R. S. and Thaddeus, P.: Astrophys. J. Letters 217, L155.
Cohen, R. S., Cong, H., Dame, T. M., and Thaddeus, P.: 1980, Astrophys. J. 239, L53.
Dame, T. M. and Thaddeus, P.: 1982, preprint.
Dodds, D., Strong, A. W., and Wolfendale, A. W.: 1975, Monthly Notices Roy. Astron. Soc. 171, 569.
Federman, S. R. and Evans, N. J.: 1981, Astrophys. J. 248, 113.
Fichtel, C. E.: 1982, ‘Status and Future of High Energy Diffuse Gamma-Ray Astronomy’, NASA Techn. Mem. 83957.
Fichtel, C. E. and Kniffen, D. A.: 1982, work in progress.
Fichtel, C. E. and Trombka, J. I.: 1981, ‘Gamma-Ray Astrophysics’, NASA SP-453.
Fichtel, C. E., Hartman, R. C., Kniffen, D. A., Thompson, D. J., Bignami, G. F., Ögelman, H., Özel, M. E., and Tümer, T.: 1975, Astrophys. J. 198, 163.
Georgelin, Y. M. and Georgelin, Y. P.: 1916, Astron. Astrophys. 49, 57.
Gordon, M. A. and Burton, W. B.: 1976, Astrophys. J. 208, 346.
Harding, A. K. and Stecker, F. W.: 1981, Nature 290, 316.
Hartman, R. C., Kniffen, D. A., Thompson, D. J., Fichtel, C. E., Ögelman, H. B., Tümer, T., and Özel, M. E.: 1979, Astrophys. J. 230, 597.
Haslam, C. G. T., Kearsey, S., Osborne, J. L., Phillipps, S., and Stoffel, H.: 1981, Nature 289, 470.
Kanbach, G. and Beuermann, K.: 1979, Proc. 16th I.C.R.C. (Kyoto) 1, 75.
Kniffen, D. A. and Fichtel, C. E.: 1981, Astrophys. J. 250, 389.
Lebrun, F., Bignami, G. F., Buccheri, R., Caraveo, P. A., Hermsen, W., Kanbach, G., Mayer-Hasselwander, H. A., Paul, J. A., Strong, A. W., and Wills, R. D.: 1982, Astron. Astrophys. 107, 390.
Lebrun, F., on behalf of the Caravane Collaboration: 1982, in F. Israel and W. B. Burton (eds.), Leiden-Workshop on Southern Galactic Surveys, D. Reidel Publ. Co., Dordrecht, Holland.
Lebrun, F., Bennett, K., Bignami, G. F., Bloemen, J. B. G. M., Buccheri, R., Caraveo, P. A., Gottwald, M., Hermsen, W., Kanbach, G., Mayer-Hasselwander, H. A., Montmerle, T., Paul, J. A., Sacco, B., Strong, A. W., Wills, R. D., Dame, T. M., Cohen, R. S., and Thaddeus, P.: 1983, Astrophys. J., is press.
Mayer-Hasselwander, H. A., Bennett, K., Bignami, G. F., Buccheri, R., D'Amico, N., Hermsen, W., Kanbach, G., Lebrun, F., Lichti, G. G., Masnou, J. L., Paul, J. A., Pinkau, K., Scarsi, L., Swanenburg, B. N., and Wills, R. D.: 1982, Astron. Astrophys. 105, 164.
Mayer-Hasselwander, H. A., on behalf of the Caravane Collaboration: 1982, in W. L. H. Shuter (ed.), Kinematics, Dynamics, and Structure of the Milky Way, D. Reidel Publ. Co., Dordrecht, Holland.
Morfill, G. E.: 1982a, Monthly Notices Roy. Astron. Soc. 198, 583.
Morfill, G. E.: 1982b, Astrophys. J., in press.
Protheroe, R. J., Strong, A. W., and Wolfendale, A. W.: 1979, Monthly Notices Roy. Astron. Soc. 188, 863.
Sanders, D. B.: 1981, ‘NRAO Workshop on Extragal. Molecules’, Greenbank, preprint.
Scarsi, L., Bennett, K., Bignami, G. F., Boella, G., Buccheri, R., Hermsen, W., Koch, L., Mayer-Hasselwander, H. A., Paul, J. A., Pfeffermann, E., Stiglitz, R., Swanenburg, B. N., Taylor, B. G., and Wills, R. D.: 1977, Proc. 12th ESLAB Symp., ESA SP-124, p. 3.
Schlickeiser, R.: 1982, Astron. Astrophys. 106, L5.
Simonson, C.: 1976, Astron. Astrophys. 46, 261.
Solomon, P. M. and Sanders, D. B.: 1980, in P. M. Solomon and E. G. Edmunds (eds.), Giant Molecular Clouds in the Galaxy, Pergamon Press, p. 41.
Stark, A. A. and Blitz, L.: 1978, Astrophys. J. Letters 225, L15.
Stecker, F. W.: 1971, Cosmic Gamma Rays, NASA SP-249.
Strong, A. W. and Lebrun, F.: 1982, Astron. Astrophys. 105, 159.
Strong, A. W., Bignami, G. F., Bloemen, J. B. G. M., Buccheri, R., Caraveo, P. A., Hermsen, W., Kanbach, G., Lebrun, F., Mayer-Hasselwander, H.A., Paul, J. A., and Wills, R. D.: 1982, Astron. Astrophys. 115, 404.
Skilling, J. and Strong, A. W.: 1976, Astron. Astrophys. 53, 253.
Swanenburg, B. N., Bennett, K., Bignami, G. F., Buccheri, R., Caraveo, P., Hermsen, W., Kanbach, G., Lichti, G. G., Masnou, J. L., Mayer-Hasselwander, H. A., Paul, J. A., Sacco, B., Scarsi, L., and Wills, R. D.: 1981, Astrophys. J. 243, L69.
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Proceedings of the XVIII General Assembly of the IAU: Galactic Astrophysics and Gamma-Ray Astronomy, held at Patras, Greece, 19 August 1982.
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Mayer-Hasselwander, H.A. Large-scale structure of the Galaxy and high-energy gamma-ray observations. Space Sci Rev 36, 223–247 (1983). https://doi.org/10.1007/BF00247089
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DOI: https://doi.org/10.1007/BF00247089