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Collimated Radiation in NGC 4151

from I - Evidence and Implications of Anisotropy in AGN

Published online by Cambridge University Press:  04 August 2010

By
G. Kriss ,
I. Evans ,
H. Ford ,
Z. Tsvetanov ,
A. Davidsen  and
A. Kinney
Edited by
Andrew Robinson  and
Roberto Juan Terlevich
G. Kriss
Affiliation:
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218.
I. Evans
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218.
H. Ford
Affiliation:
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218.
Z. Tsvetanov
Affiliation:
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218.
A. Davidsen
Affiliation:
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218.
A. Kinney
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218.
Andrew Robinson
Affiliation:
University of Cambridge
Roberto Juan Terlevich
Affiliation:
Royal Greenwich Observatory, Cambridge
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Summary

Abstract

We present a [O III] λ5007 image of the nuclear region of the Seyfert 1 galaxy NGC 4151 obtained with the Planetary Camera on the Hubble Space Telescope. The [O III] image shows a striking biconical structure centred on the bright, unresolved central source. Simple geometric arguments place our line of sight outside the cone of ionizing radiation. Since we have a nearly unobstructed view of the UV continuum and broad-line region, an optically thick molecular torus cannot be the source of the collimation. Lower column density material visible in UV spectra is largely transparent at UV and optical wavelengths, but opaque beyond the Lyman limit. It can collimate the ionizing radiation field without obscuring our view of the central engine.

The simplest unified models of Seyfert 1 and Seyfert 2 galaxies invoke a dense, optically thick, molecular torus surrounding the central engine and broad-line region which serves as both a shield which prevents us from viewing the centres of Seyfert 2's and as the source of the collimation for the ionizing radiation. The difference between Seyfert 1's and Seyfert 2's is then due entirely to the opening angle of the torus and its orientation relative to our line of sight. The observations presented here and by Evans et al. present a direct challenge to this simple view.

Figure 1 shows the raw image obtained with the Planetary Camera on the Hubble Space Telescope through the F502N filter in a 1608 s exposure.

Type
Chapter
Information
The Nature of Compact Objects in Active Galactic Nuclei
Proceedings of the 33rd Herstmonceux Conference, held in Cambridge, July 6-22, 1992
 , pp. 46 - 47
Publisher: Cambridge University Press
Print publication year: 1994

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  • Collimated Radiation in NGC 4151
    • By G. Kriss, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., I. Evans, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218., H. Ford, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218., Z. Tsvetanov, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., A. Davidsen, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., A. Kinney, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218.
  • Edited by Andrew Robinson, University of Cambridge, Roberto Juan Terlevich, Royal Greenwich Observatory, Cambridge
  • Book: The Nature of Compact Objects in Active Galactic Nuclei
  • Online publication: 04 August 2010
  • Chapter DOI: https://doi.org/10.1017/CBO9780511564765.010
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  • Collimated Radiation in NGC 4151
    • By G. Kriss, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., I. Evans, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218., H. Ford, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218., Z. Tsvetanov, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., A. Davidsen, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., A. Kinney, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218.
  • Edited by Andrew Robinson, University of Cambridge, Roberto Juan Terlevich, Royal Greenwich Observatory, Cambridge
  • Book: The Nature of Compact Objects in Active Galactic Nuclei
  • Online publication: 04 August 2010
  • Chapter DOI: https://doi.org/10.1017/CBO9780511564765.010
Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Collimated Radiation in NGC 4151
    • By G. Kriss, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., I. Evans, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218., H. Ford, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218., Z. Tsvetanov, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., A. Davidsen, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218., A. Kinney, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218.
  • Edited by Andrew Robinson, University of Cambridge, Roberto Juan Terlevich, Royal Greenwich Observatory, Cambridge
  • Book: The Nature of Compact Objects in Active Galactic Nuclei
  • Online publication: 04 August 2010
  • Chapter DOI: https://doi.org/10.1017/CBO9780511564765.010
Available formats
×