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Radiative acceleration of gas in quasars


QUASARS can radiate up to a thousand times the energy of the entire Galaxy, yet this energy is generated in a small region approximately one light day across. (By comparison, the diameter of the Milky Way is about 100,000 light years.) Because of the high energy density in this region, it has often been suggested that radiation pressure might play an important dynamical role in quasars1á¤-3. Here we show that radiative acceleration can readily explain a prominent feature observed in the spectra of several broad-absorption-line (BAL) quasars. The broad absorption lines are themselves attributed to matter flowing towards the observer with velocities approaching one-tenth of the speed of light4,5, and our results suggest that radiative acceleration is the dominant driving mechanism in these outflows. As most quasars are believed to have BAL outflows6 (although they are seen in only about 10% of them because of viewing angle7,8), radiative acceleration is likely to be an important dynamical process in quasars in general.

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  1. Scargle, J. D., Caroff, L. J. & Noerdlinger, P. D. Astrophys. J. 161, L115–L121 (1970).

    ADS  Article  Google Scholar 

  2. McKee, C. F. & Tarter, C. B. Astrophys. J. 202, 306–318 (1975).

    ADS  CAS  Article  Google Scholar 

  3. Drew, J. E. & Boksenberg, A. Mon. Not. R. astr. Soc. 211, 813–831 (1984).

    ADS  CAS  Article  Google Scholar 

  4. Weymann, R. J., Turnshek, D. A. & Christiansen, W. A. in Astrophysics of Active Galaxies and Quasi-stellar Objects (ed. Miller, J.) 333–365 (Oxford Univ. Press, 1985).

    Google Scholar 

  5. Turnshek, D. A. in Proc. 2nd Symp. Space Telescope Science Inst. (eds Blades, S. C, Turnshek, D. A. & Norman, C. A.) 17–51 (Cambridge Univ. Press, 1988).

    Google Scholar 

  6. Weymann, R. J., Morris, S. L., Foltz, C. B. & Hewett, P. C. Astrophys. J. 373, 23–53 (1991).

    ADS  CAS  Article  Google Scholar 

  7. Foltz, C. B., Chafee, F. H., Hewett, P. C., Weymann, R. J. & Morris, S. L. Bull. Am. astr. Soc. 2, 806 (1990).

    ADS  Google Scholar 

  8. Hamann, F., Korista, T. K. & Morris, S. L. Astrophys. J. 415, 541–562 (1993).

    ADS  CAS  Article  Google Scholar 

  9. Turnshek, D. A., Foltz, C. B., Grillmair, C. J. & Weymann, R. J. Astrophys. J. 325, 651–670 (1988).

    ADS  CAS  Article  Google Scholar 

  10. Korista, T. K., Voit, G. M., Morris, S. L. & Weymann, R. J. Astrophys. J. Suppl. Ser. 88, 357–381 (1993).

    ADS  CAS  Article  Google Scholar 

  11. Arav, N. & Begelman, M. C. Astrophys. J. 434, 479–483 (1994).

    ADS  CAS  Article  Google Scholar 

  12. Netzer, H. in Active Galactic Nuclei (eds Blandford, R. D., Netzer, H. & Woltjer, L.) 57–160 (Springer, New York, 1990).

    Google Scholar 

  13. Arav, N., Li, Z. Y. & Begelman, M. C. Astrophys. J. 432, 62–74 (1994).

    ADS  CAS  Article  Google Scholar 

  14. Mathews, W. G. & Ferland, G. J. Astrophys. J. 323, 456–467 (1987).

    ADS  CAS  Article  Google Scholar 

  15. Michalitsianos, A. G. & Oliversen, R. J. Astrophys. J. 439, 599–603 (1995).

    ADS  CAS  Article  Google Scholar 

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Arav, N., Korista, K., Barlow, T. et al. Radiative acceleration of gas in quasars. Nature 376, 576–578 (1995).

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