Skip to main content

Thank you for visiting nature.com. 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.

  • Letter
  • Published:

Visibility of scattered broad-line emission in Seyfert 2 galaxies

Abstract

Active galaxies are thought to be powered by the accretion of gas onto a central massive black hole. Seyfert galaxies—the most common examples of nearby active galaxies—are separated into two classes based on their emission line widths1. Seyfert 1 galaxies exhibit broad emission lines that are attributed to ionized gas within 1 pc of the black hole, whereas the spectra of Seyfert 2 galaxies show only narrower emission lines, believed to originate from a much larger region around the core. The 'unified model' for Seyfert galaxies attributes these differences to the presence of a dusty torus of dense molecular gas surrounding the black hole2: the orientation of Seyfert 2 galaxies is such that the broad-line region is obscured. The detection3 in the polarization spectrum of broad emission lines scattered into our line of sight by free electrons in NGC1068 (the prototypical Seyfert 2 galaxy) and other Seyfert 2 galaxies4–8 has strengthened this view, but all of these galaxies were subject to selection biases. Here we report the results of a systematic search for polarized broad emission lines in a well defined sample of Seyfert 2 galaxies. We show that the ability to detect scattered broad emission lines is related to the far-infrared colours, in the manner predicted by the unified model.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others

References

  1. Osterbrock, D. E. Astrophysics of Gaseous Nebulae and Active Galactic Nuclei 308–381 (University Science Books, Mill Valley, USA, 1989).

    Book  Google Scholar 

  2. Antonucci, R. R. J. Annu. Rev. Astron. Astrophys. 31, 473–521 (1993).

    Article  ADS  CAS  Google Scholar 

  3. Antonucci, R. R. J. & Miller, J. S. Astrophys. J. 297, 621–632 (1985).

    Article  ADS  CAS  Google Scholar 

  4. Miller, J. S. & Goodrich, R. W. Astrophys. J. 355, 456–467 (1990).

    Article  ADS  CAS  Google Scholar 

  5. Tran, H., Miller, J. S. & Kay, L. Astrophys. J. 397, 452–456 (1992).

    Article  ADS  CAS  Google Scholar 

  6. Inglis, M. D. et al. Mon. Not. R. Astron. Soc. 263, 895–902 (1993).

    Article  ADS  CAS  Google Scholar 

  7. Young, S. et al. Mon. Not. R. Astron. Sco. 281, 1206–1242 (1996).

    Article  ADS  CAS  Google Scholar 

  8. Hines, D. C. & Wills, B. J. Astrophys. J. 415, 82–92 (1993).

    Article  ADS  Google Scholar 

  9. Hutchings, J. B. & Neff, S. G. Astron. J. 101, 434–446 (1991).

    Article  ADS  CAS  Google Scholar 

  10. Kay, L. in The First Stromlo Symposium: The Physics of Active Galaxies (eds Bicknell, G. V., Dopita, M. A. & Quinn, P. J.) 265–266 (ASP Conf. Sen Vol. 54, Astron. Soc. Pacific, San Francisco, 1994).

    Google Scholar 

  11. Roy, A. L., Norris, R. P., Kesteven, M. J., Troup, E. R. & Reynolds, J. E. Astrophys. J. 432, 496–507 (1994).

    Article  ADS  Google Scholar 

  12. Heisler, C. A., Norris, R. P., Jauncey, D. L., Reynolds, J. E. & King, E. A. in Proc. 4th Asia Pacific Meeting and Workshop (ed. King, E. A.) 166–177 (ATNF, Sydney, Australia, 1996).

    Google Scholar 

  13. Norris, R. P., Allen, D. A., Sramek, R. A., Kesteven, M. J. & Troup, E. R. Astrophys. J. 359, 291–295 (1990).

    Article  ADS  Google Scholar 

  14. Pier, E. A. & Krolik, J. H. Astrophys. J. 418, 673–686 (1993).

    Article  ADS  Google Scholar 

  15. Granato, G. L. & Danese, L. Mon. Not. R. Astron. Soc. 268, 235–252 (1994).

    Article  ADS  Google Scholar 

  16. Efstathiou, A. & Rowan-Robinson, M. Mon. Not. R. Astron. Soc. 273, 649–661 (1995).

    Article  ADS  Google Scholar 

  17. Giuricin, G., Mardirossian, E. & Mezzetti, M. Astrophys. J. 446, 550–560 (1995).

    Article  ADS  Google Scholar 

  18. Maiolino, R., Ruiz, M., Rieke, G. H. & Keller, L. D. Astrophys. J. 446, 561–573 (1995).

    Article  ADS  Google Scholar 

  19. Spinoglio, L., Malkan, M. A., Rush, B., Carrasco, L. & Recillas-Cruz, E. Astrophys. J. 453, 616–633 (1995).

    Article  ADS  Google Scholar 

  20. Young, S., Hough, J. H., Axon, D. J., Bailey, J. A. & Ward, M. J. Mon. Not. R. Astron. Soc. 272, 513–527 (1995).

    Article  ADS  Google Scholar 

  21. Pogge, R. W. Astrophys. J. 345, 730–751 (1989).

    Article  ADS  CAS  Google Scholar 

  22. Veilleux, S., Kim, D.-C., Sanders, D. B., Mazzarella, J. M. & Soifer, B. T. Astrophys. J. Suppl. Ser. 98, 171–217 (1995).

    Article  ADS  CAS  Google Scholar 

  23. Veron-Cetty, M.-P. & Veron, P. Astron. Astrophys. Suppl. Ser. 65, 241–258 (1986).

    ADS  CAS  Google Scholar 

  24. Mulchaey, J. S., Wilson, A. S. & Tsvetanov, Z. Astrophys. J. Suppl Ser. 102, 309–367 (1996).

    Article  ADS  CAS  Google Scholar 

  25. Osterbrock, D. E. & Dahari, O. Astrophys. J. 273, 478–488 (1983).

    Article  ADS  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Rights and permissions

Reprints and permissions

About this article

Cite this article

Heisler, C., Lumsden, S. & Bailey, J. Visibility of scattered broad-line emission in Seyfert 2 galaxies. Nature 385, 700–702 (1997). https://doi.org/10.1038/385700a0

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/385700a0

This article is cited by

Comments

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.

Search

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