Collimating the ionizing radiation in AGN

Zlatan Tsvetanov, G. A. Kriss, H. C. Ford

Research output: Contribution to journalArticle


The hard-edged ionization cone seen by the HST imaging of NGC 4151 and the line-of-sight gas observed in some Seyfert 1 galaxies present a strong challenge for the simplest version of the Unified Model of AGN, which predicts that bi-conically shaped EELR can be observed only in type 2 objects and the line-of-sight to type 1 nucleus must be clear. To accommodate these rather contradictory requirements we suggest a modification of the shadowing/obscuration scenario. In our model the collimation of the ionizing radiation is provided by a partially neutral atmosphere surrounding the physically thin, dense torus. This atmosphere provides a natural way of producing wide angle ionization cones and at the same time allows for a relatively clear view of the central regions for some angles outside the cone edges. The model has an observationally testable predictions. Recently discovered nuclear disks in some elliptical galaxies hosting AGN may provide a natural way of supplying the gas for both the torus and the atmosphere surrounding it.

Original languageEnglish
Pages (from-to)71-75
Number of pages5
JournalVistas in Astronomy
Issue number1
Publication statusPublished - 1996
Externally publishedYes


ASJC Scopus subject areas

  • Astronomy and Astrophysics

Cite this

Tsvetanov, Z., Kriss, G. A., & Ford, H. C. (1996). Collimating the ionizing radiation in AGN. Vistas in Astronomy, 40(1), 71-75.