From Fairall 9 to high-z objects - Pattern of change in ionization structure

Abstract

view Abstract Citations (21) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS From Fairall 9 to High-z Objects: Pattern of Change in Ionization Structure Zheng, Wei ; Fang, Li-Zhi ; Binette, Luc Abstract A study of 79 IUE spectra of the Seyfert galaxy Fairall 9 shows a considerable change in the continuum shape which can be characterized by several sections. The flux at 3075 A changes in approximate proportion to the optical and X-ray flux, suggesting that they may be a part of the power law. The apparent fourfold change in the continuum slope between 1826 and 3075 A indicates a considerably different variations for the UV bump and the power-law continuum. The most variable part between 1338 and 1826 A keeps a constant slope. Significant differential variations are found in weaker emission lines, including N v λ1240, Si IV λ1400, He II λ1640, and C III] λ1909. Low-ionization lines (threshold energy between 1 and 3 Ry) appear to follow the UV bump, and high-ionization lines follow the power-law continuum. The results, in addition to the previous report on strong lines, suggest that the variation amplitude of lines is inversely correlated to the effective excitation level. Our multiline fit suggests that the UV bump has a shape more complicated than a simple black-body curve and its high-energy tail extends beyond 3 eV. An active galactic nucleus statistic finds that the degree of luminosity dependence of equivalent width is inversely correlated with individual emission line's excitation level. This offers a natural explanation as to why the C IV equivalent width shows the most significant luminosity dependence (the Baldwin effect). We suggest a more prominent UV bump in high states or in high-luminosity objects. Publication: The Astrophysical Journal Pub Date: June 1992 DOI: 10.1086/171406 Bibcode: 1992ApJ...392...74Z Keywords: Active Galactic Nuclei; Photoionization; Seyfert Galaxies; Ultraviolet Spectra; Continuous Spectra; Emission Spectra; Forbidden Transitions; Iron; Iue; Line Spectra; Magnesium; Spectrum Analysis; Astrophysics; GALAXIES: INDIVIDUAL NAME: FAIRALL 9; GALAXIES: NUCLEI; GALAXIES: SEYFERT; ULTRAVIOLET: GALAXIES full text sources ADS | data products SIMBAD (2) NED (1) MAST (1) INES (1)