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

Abstract

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

15 pages, 13 figures

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• The picture of BLR in 2.5-D FRADO: Dynamics & Geometry
• Reverberation Mapping Measurements of Black Hole Masses and Broad-Line Region Kinematics in Mrk 817 and NGC 7469
• Radiation pressure on dust explains the Low Ionized Broad Emission Lines in Active Galactic Nuclei
• Long-term optical spectroscopic variations in blazar 3C 454.3
• What shapes the Absorption Measure Distribution in AGN outflows
• Quasar main sequence in the UV plane
• The multi-phase environment in the centre of Centaurus A
• Emission lines from X-ray illuminated accretion disc in black hole binaries
• Ultradense Gases beyond Dusty Torus in a Partially Obscured Quasar
• AGN in the ULIRG HE 0435-5304
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