Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

The rotating wind of the quasar PG 1700+518


It is now widely accepted that most galaxies undergo an active phase, during which a central super-massive black hole generates vast radiant luminosities through the gravitational accretion of gas1,2. Winds launched from a rotating accretion disk surrounding the black hole are thought to play a critical role, allowing the disk to shed angular momentum that would otherwise inhibit accretion3,4. Such winds are capable of depositing large amounts of mechanical energy in the host galaxy and its environs, profoundly affecting its formation and evolution5,6,7, and perhaps regulating the formation of large-scale cosmological structures in the early Universe8,9. Although there are good theoretical grounds for believing that outflows from active galactic nuclei originate as disk winds10, observational verification has proven elusive. Here we show that structures observed in polarized light across the broad Hα emission line in the quasar PG 1700+518 originate close to the accretion disk in an electron scattering wind. The wind has large rotational motions (4,000 km s-1), providing direct observational evidence that outflows from active galactic nuclei are launched from the disks. Moreover, the wind rises nearly vertically from the disk, favouring launch mechanisms that impart an initial acceleration perpendicular to the disk plane.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: The polarization data for the BAL quasar PG1700+518.
Figure 2: Comparison of simulated polarization spectra for different scattering geometries.
Figure 3: A cross-section schematic illustration of the wind geometry inferred from the polarization and spectroscopic properties of PG1700+518.


  1. 1

    Rees, M. J. Black hole models for active galactic nuclei. Annu. Rev. Astron. Astrophys. 22, 471–506 (1984)

    CAS  ADS  Article  Google Scholar 

  2. 2

    Ferrarese, L. & Ford, H. Supermassive black holes in galactic nuclei: Past, present and future research. Space Sci. Rev. 116, 523–624 (2005)

    ADS  Article  Google Scholar 

  3. 3

    Crenshaw, D. M., Kraemer, S. B. & George, I. M. Mass loss from the nuclei of active galaxies. Annu. Rev. Astron. Astrophys 41, 117–167 (2003)

    ADS  Article  Google Scholar 

  4. 4

    Blandford, R. D. & Payne, D. G. Hydromagnetic flows from accretion discs and the production of radio jets. Mon. Not. R. Astron. Soc. 199, 883–903 (1982)

    ADS  Article  Google Scholar 

  5. 5

    Silk, J. & Rees, M. J. Quasars and galaxy formation. Astron. Astrophys. 331, L1–L4 (1998)

    ADS  Google Scholar 

  6. 6

    Scannapieco, E., Silk, J. & Bouwens, R. AGN feedback causes downsizing. Astrophys. J. 635, L13–L16 (2005)

    ADS  Article  Google Scholar 

  7. 7

    Di Matteo, T., Springel, V. & Hernquist, L. Energy input from quasars regulates the growth and activity of black holes and their host galaxies. Nature 433, 604–607 (2005)

    CAS  ADS  Article  Google Scholar 

  8. 8

    Bower, R. G. et al. Breaking the hierarchy of galaxy formation. Mon. Not. R. Astron. Soc. 370, 645–655 (2006)

    CAS  ADS  Article  Google Scholar 

  9. 9

    Menci, N., Fontana, A., Giallongo, E., Grazian, A. & Salimbeni, S. The abundance of distant and extremely red galaxies: The role of AGN feedback in hierarchical models. Astrophys. J. 647, 753–762 (2006)

    CAS  ADS  Article  Google Scholar 

  10. 10

    Shlosman, I., Vitello, P. A. & Shaviv, G. Active galactic nuclei — Internal dynamics and formation of emission clouds. Astrophys. J. 294, 96–105 (1985)

    CAS  ADS  Article  Google Scholar 

  11. 11

    Turnshek, D. A. Properties of the broad absorption-line QSOs. Astrophys. J. 280, 51–65 (1984)

    CAS  ADS  Article  Google Scholar 

  12. 12

    Reichard, T. A. et al. Continuum and emission-line properties of broad absorption line quasars. Astron. J. 126, 2594–2607 (2003)

    CAS  ADS  Article  Google Scholar 

  13. 13

    Weymann, R. J., Morris, S. L., Foltz, C. B. & Hewett, P. C. Comparisons of the emission-line and continuum properties of broad absorption line and normal quasi-stellar objects. Astrophys. J. 373, 23–53 (1991)

    CAS  ADS  Article  Google Scholar 

  14. 14

    Pettini, M. & Boksenberg, A. PG 1700+518 — A low-redshift, broad absorption line QSO. Astrophys. J. 294, L73–L78 (1985)

    CAS  ADS  Article  Google Scholar 

  15. 15

    Schmidt, G. D. & Hines, D. C. The polarization of broad absorption line QSOs. Astrophys. J. 512, 125–135 (1999)

    CAS  ADS  Article  Google Scholar 

  16. 16

    Ogle, P. M. et al. Polarization of broad absorption line QSOs. I. A spectropolarimetric atlas. Astrophys. J. Suppl. Ser. 125, 1–34 (1999)

    CAS  ADS  Article  Google Scholar 

  17. 17

    Rokaki, E. & Boisson, C. Consistency of accretion discs with Seyfert 1 UV fluxes and Hβ emission-line profiles. Mon. Not. R. Astron. Soc. 307, 41–54 (1999)

    CAS  ADS  Article  Google Scholar 

  18. 18

    Smith, J. E., Robinson, A., Young, S., Axon, D. J. & Corbett, E. A. Equatorial scattering and the structure of the broad-line region in Seyfert nuclei: Evidence for a rotating disc. Mon. Not. R. Astron. Soc. 359, 846–864 (2005)

    CAS  ADS  Article  Google Scholar 

  19. 19

    Young, S., Robinson, A., Axon, D. J. & Hough, J. H. Polarization signatures of disc-winds. Astrophys. J. (submitted)

  20. 20

    Barvainis, R. Hot dust and the near-infrared bump in the continuum spectra of quasars and active galactic nuclei. Astrophys. J. 320, 537–544 (1987)

    ADS  Article  Google Scholar 

  21. 21

    Peterson, B. M. et al. Central masses and broad-line region sizes of active galactic nuclei. II. A homogeneous analysis of a large reverberation-mapping database. Astrophys. J. 613, 682–699 (2004)

    CAS  ADS  Article  Google Scholar 

  22. 22

    Murray, N., Chiang, J., Grossman, S. A. & Voit, G. M. Accretion disk winds from active galactic nuclei. Astrophys. J. 451, 498–509 (1995)

    CAS  ADS  Article  Google Scholar 

  23. 23

    de Kool, M. & Begelman, M. C. Radiation pressure-driven magnetic disk winds in broad absorption line quasi-stellar objects. Astrophys. J. 455, 448–455 (1995)

    ADS  Article  Google Scholar 

  24. 24

    Proga, D., Stone, J. M. & Kallman, T. R. Dynamics of line-driven disk winds in active galactic nuclei. Astrophys. J. 543, 686–696 (2000)

    ADS  Article  Google Scholar 

  25. 25

    Begelman, M. C., McKee, C. F. & Shields, G. A. Compton heated winds and coronae above accretion disks. I Dynamics. Astrophys. J. 271, 70–88 (1983)

    CAS  ADS  Article  Google Scholar 

  26. 26

    Stone, J. M. & Norman, M. L. Numerical simulations of magnetic accretion disks. Astrophys. J. 433, 746–756 (1994)

    ADS  Article  Google Scholar 

  27. 27

    Proga, D. & Kallman, T. R. Dynamics of line-driven disk winds in active galactic nuclei. II. Effects of disk radiation. Astrophys. J. 616, 688–695 (2004)

    ADS  Article  Google Scholar 

  28. 28

    Elvis, M. A Structure for quasars. Astrophys. J. 545, 63–76 (2000)

    ADS  Article  Google Scholar 

  29. 29

    Oudmaijer, R. D., Proga, D., Drew, J. E. & de Winter, D. The evolved B[e] star HD 87643: Observations and radiation driven disk-wind model for B[e] stars. Mon. Not. R. Astron. Soc. 300, 170–182 (1998)

    CAS  ADS  Article  Google Scholar 

  30. 30

    Young, S. A generic scattering model for AGN. Mon. Not. R. Astron. Soc. 312, 567–578 (2000)

    ADS  Article  Google Scholar 

Download references


This work is based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. This research has made use of NASA’s Astrophysics Data System. We acknowledge financial support from the Science and Technology Facilities Council, UK.

Author Contributions All authors contributed extensively to the work presented in this paper.

Author information



Corresponding author

Correspondence to S. Young.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Figures

The file contains Supplementary Figures 1-5 with Legends. These figures illustrate the model output for (1) thermal motions of the scattering elements; (2) different scattering geometries (a colour version of Figure 2 from the main article); (3) cylindrical winds with different outflow and rotational velocities; (4) cylindrical winds with extending to differing vertical heights and (5) cylindrical winds launched from differing radii on the accretion disc. (PDF 421 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Young, S., Axon, D., Robinson, A. et al. The rotating wind of the quasar PG 1700+518. Nature 450, 74–76 (2007).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing