Intermediate-line Emission in AGNs: The Effect of Prescription of the Gas Density

T. P. Adhikari, K. Hryniewicz, A. Rózańska, B. Czerny, G. J. Ferland

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The requirement of an intermediate-line component in the recently observed spectra of several active galactic nuclei (AGNs) points to the possible existence of a physically separate region between the broad-line region (BLR) and narrow-line region (NLR). In this paper we explore the emission from the intermediate-line region (ILR) by using photoionization simulations of the gas clouds distributed radially from the center of the AGN. The gas clouds span distances typical for the BLR, ILR, and NLR, and the appearance of dust at the sublimation radius is fully taken into account in our model. The structure of a single cloud is calculated under the assumption of constant pressure. We show that the slope of the power-law radial profile of the cloud density does not affect the existence of the ILR in major types of AGNs. We found that the low-ionization iron line, Fe ii, appears to be highly sensitive to the presence of dust and therefore becomes a potential tracer of dust content in line-emitting regions. We show that the use of a disk-like cloud density profile computed for the upper part of the atmosphere of the accretion disk reproduces the observed properties of the line emissivities. In particular, the distance of the Hβ line inferred from our model agrees with that obtained from reverberation mapping studies in the Sy1 galaxy NGC 5548.

Original languageEnglish
Article number78
JournalAstrophysical Journal
Issue number1
StatePublished - Mar 20 2018

Bibliographical note

Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved..


  • galaxies: active
  • methods: numerical
  • quasars: emission lines
  • radiative transfer

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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