The broad emission lines in the active galactic nucleus Fairall 9

Abstract

This paper reports on a study of UV and optical spectra of the active galaxy Fairall 9 taken as a part of the International AGN Watch database. CIV/Lyα, Lyα/Hß and Hα/Hß ratios have been measured at different radial velocities, which are varied across the line profiles. The ratio Lyα/Hß is low in the low-velocity centre of the lines, but increases a little in the high-velocity wings. The CIV/Lα and Hα/Hß line intensities ratios, however, are high at the line centre but become low in the wings. Modelling with the photoionization code CLOUDY shows that the observed line ratios can be described by two systems of clouds. One corresponds to the high-ionization line zone (HIL) with an electron density, n_e∼ 10⁸⁻¹⁰ cm⁻³. It is presumably located above the accretion disk or in the jets. The other system corresponds to the low-ionization line zone (LIL), which is probably a part of the accretion disk and which has a higher electron density, n_e∼ 10¹²⁻¹³ cm⁻³. The possible geometry of the BLR in Fairall 9 is discussed.

Keywords:

• Active galactic nuclei
• Seyfert galaxies
• Broad line regions
• Photoionization modelling

Acknowledgements

This research has been partially supported by RFBR grant 06-02-16843.