Hostname: page-component-78c5997874-fbnjt Total loading time: 0 Render date: 2024-11-17T16:55:23.307Z Has data issue: false hasContentIssue false
  • English
  • Français

Quasars: Their Evolution, Absorption Lines and the Intergalactic Gas

Published online by Cambridge University Press:  25 April 2016

G. Setti

Extract

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.

For many years now it has been known that the number vs. magnitude counts of quasars is the prima facie evidence of a cosmological evolution of this class of objects. Down to an apparent magnitude B - 19 the number of quasars increases by almost a factor 8 per magnitude Interval, compared to a factor 4 obtained in an Euclidean universe filled with a uniform distribution of sources, and correspondingly less for the classical Friedmann models of Gen. Relativity due to the red-shift effects. This strong evolution has been recently questioned because of several biases which may artificially steepen the slope of the counts in the optical surveys. Deep surveys of quasars selected via multi-colour techniques down to B - 23 have confirmed the long standing inference that the number count relationship must flatten beyond B - 20. As a consequence, pure density evolution models, where only the number density of quasars increases with the redshift z, leaving unchanged the shape of the local luminosity function, are ruled out, since too many quasars are predicted at faint magnitudes compared to the dramatic flattening of the counts (see, e.g., ref. 4).

Type
Research Article
Information
Transactions of the International Astronomical Union , Volume 20 , Issue 1 , 1988 , pp. 666 - 670
Copyright
Copyright © Kluwer 1988 

References

1 – Wampler, E.J. and Ponz, D.: 1985, Astrophys. J. 298, pp. 448.CrossRefGoogle Scholar
2 – Koo, D.C.: 1986, in “Structure and Evolution of Active Galactic Nuclei”, Giuricin, G. et al. (eds.), Reidel, Dordrecht, Astrophys. Spa. Sci. Library 121, pp. 317.Google Scholar
3 – Koo, D.C., Kron, R.G. and Cudworth, L.M.: 1986, P.A.S.P. 98, pp. 285.CrossRefGoogle Scholar
Marano, B., Zamorani, G. and Zitelli, V.: 1986, in “Structure and Evolution of Active Galactic Nuclei”, Giuricin, G. et al. (eds.), Reidel, Dordrecht, Astrophys. Spa. Sci. Library 121, pp. 339.CrossRefGoogle Scholar
4 – Setti, G.: 1984, in “X-Ray and UV Emission from Active Galactic Nuclei, Brinkmann, W. and Trümper, J. (eds.), MPE Report 184, pp. 243.Google Scholar
5 – Boyle, B.J., et al.: 1987, Mon. Not. R. astr. Soc. 227, pp. 717.CrossRefGoogle Scholar
6 – Weedman, D.W.: 1986, in “Structure and Evolution of Active Galactic Nuclei”, Giuricin, G. et al. (eds.), Reidel, Dordrecht, Astrophys. Spa. Sci. Library 121, pp. 215.CrossRefGoogle Scholar
7 – Marshall, H.L.: 1985, Astrophys. J. 299, pp. 109.CrossRefGoogle Scholar
8 – Koo, D.C., and Kron, R.G.: 1987, in IAU Symp. 124 on “Observational Cosmology”, Hewitt, A., Burbidge, G. and Zhi Fang, L. (eds.), Reidel, Dordrecht, pp. 383.Google Scholar
9 – Schmidt, M.: 1987, in IAU Symp. 124 on “Observational Cosmology”, Hewitt, A., Burbidge, G. and Zhi Fang, L. (eds.), Reidel, Dordrecht, pp. 619.Google Scholar
10 – Cavaliere, A., Giallongo, E. and Vagnetti, F.: 1985, Astrophys. J. 296, pp. 402.CrossRefGoogle Scholar
11 – Setti, G. and Zamorani, G.: 1984, in COSPAR/IAU Symp. on “High Energy Astrophysics and Cosmology”, Bignami, G.F. and Sunyaev, R.A. (eds.), Advances Spa. Res. 3, pp. 175.CrossRefGoogle Scholar
12 – Schmidt, M., Schneider, D.P. and Gunn, J.E.: 1987, Astrophys. J. 316, pp. L1.CrossRefGoogle Scholar
13 – Véron, P.: 1986, Astron. Astrophys. 170, pp. 37.Google Scholar
14 – Ostriker, J.P. and Heisler, J.: 1984, Astrophys. J. 278, pp. 1.CrossRefGoogle Scholar
15 – Wrigth, E.L.: 1986, Astrophys. J. 311, pp. 156.Google Scholar
Malkan, M.: 1986, in IAU Symp. 119 on “Quasars”, Swarup, and Kapahi, V.K. (eds.), Reidel, Dordrecht, pp. 453.Google Scholar
16 – Hewett, P.C.: 1987, private communication.Google Scholar
17 – Hewett, P.C.: 1987, in IAU Symp. 124 on “Observational Cosmology”, Hewitt, A., Burbidge, G. and Zhi Fang, L. (eds.), Reidel, Dordrecht, pp. 664.Google Scholar
18 – Avny, Y. and Tananbaum, H.: 1986, Astrophy. J. 305, pp. 83.CrossRefGoogle Scholar
19 – Gioia, I.M., et al.: 1984, Astrophys. J. 283, pp. 495.CrossRefGoogle Scholar
20 – Schmidt, M. and Green, R.F.: 1986, Astrophys. J. 305, pp. 68.CrossRefGoogle Scholar
21 – Setti, G.: 1987, in IAU Symp. 124 on “Observational Cosmology”, Hewitt, A., Burbidge, G. and Zhi Fang, L. (eds.), Reidel, Dordrecht, pp. 579.Google Scholar
22 – Franceschini, A., Gioia, I.M. and Maccacaro, T.: 1986, Astrophys. J. 301, pp. 124 CrossRefGoogle Scholar
23 – Wall, J.V., and Peacock, J.A.: 1985, Mon. Not. R. astr. Soc. 216, pp. 173.CrossRefGoogle Scholar
24 – Savage, A., et al.: 1987, in IAU Symp. 124 on “Observational Cosmology”, Hewitt, A., Burbidge, G. and Zhi Fang, L. (eds.), Reidel, Dordrecht, pp. 673.Google Scholar
25 – Peacock, J.A. and Dunlop, J.S.: 1986, in IAU Symp. 124 on “Observational Cosmology”, Hewitt, A., Burbidge, G. and Zhi Fang, L. (eds.), Reidel, Dordrecht, pp. 455.Google Scholar
26 – Downes, A.J.B., et al.: 1986, Mon. Not. R. astr. Soc. 218, pp. 31.CrossRefGoogle Scholar
27 – Vietri, M.: 1985, Astrophys. J. 293. pp. 343.CrossRefGoogle Scholar
28 – Ostriker, J.P. and Vietri, M.: 1986, Astrophys. J. 300, pp. 68.CrossRefGoogle Scholar
29 – Schneider, P.: 1986, Astr. Astrophys., submitted (MPA 218, preprint).Google Scholar
30 – Segal, I.E. and Nicoll, J.F.: 1986, Astrophys. J. 300, pp. 224.CrossRefGoogle Scholar
31 – Wright, E.L.: 1987, Astrophys. J. 313, pp. 551.CrossRefGoogle Scholar
32 – Shanks, T., et al.: 1987, Mon. Not. R. astr. Soc. 227, pp. 739.CrossRefGoogle Scholar
33 – Clowes, R.G., Iovino, A. and Shaver, P.: 1987, Mon. Not. R. astr. Soc. 227, pp. 921.CrossRefGoogle Scholar
34 – Crampton, D., Cowley, A.P. and Hastwick, F.D.A.: 1987, Astrophys. J. 311, pp. 129.CrossRefGoogle Scholar
35 – Sargent, W.L.W.: 1987, in IAU Symp. 124 on “Observational Cosmology”, Hewitt, A., Burbidge, G. and Zhi Fang, L. (eds.), Reidel, Dordrecht, pp. 777.Google Scholar
36 – Rees, M.J.: 1986, Mon. Not. R. astr. Soc. 218, pp. 25p.CrossRefGoogle Scholar
37 – Tytler, D.: 1987, Astrophys. J. 321, pp. 49.CrossRefGoogle Scholar
38 – Foltz, C.B., et al.: 1984, Astrophys. J. 281, pp. L1.CrossRefGoogle Scholar
39 – Wolfe, A.M., et al.: 1986, Astrophys. J. Suppl. 61, pp. 249.CrossRefGoogle Scholar
40 – Smith, H.E., Cohen, R.D. and Bradley, S.E.: 1986, Astrophys. J. 310, pp. 583.CrossRefGoogle Scholar
41 – Murdoch, H.S., et al.: 1986, Astrophys. J. 309, pp. 19.CrossRefGoogle Scholar
42 – Tytler, D.: 1987, Astrophys. J. 321, pp. 69.CrossRefGoogle Scholar
43 – Carswell, R.F. and Rees, M.J.: 1987, Mon. Not. R. astr. Soc. 224, pp. 13p.CrossRefGoogle Scholar
44 – Steidel, C.C. and Sargent, W.L.W.: 1987, Astrophys. J. 318, pp. L11.CrossRefGoogle Scholar