Continuum and Emission-Line Strength Relations for a Large Active Galactic Nuclei Sample

By M. Dietrich, F. Hamann, J. Shields, A. Constantin, M. Vestergaard, F. Chaffee, C. Foltz, V. Junkkarinen. 2002

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We report on the analysis of a large sample of 744 type 1 active galactic nuclei, including quasars and Seyfert 1 galaxies across the redshift from 0 ≲ z ≲ 5 and spanning nearly 6 orders of magnitude in continuum luminosity. We discuss correlations of continuum and emission-line properties in the rest-frame ultraviolet and optical spectral ranges. The well-established Baldwin effect is detected for almost all emission lines from O VI λ1034 to [O III] λ5007. Their equivalent widths are significantly anticorrelated with the continuum strength, while they are nearly independent of redshift. This is the well-known Baldwin effect. Its slope β, measured as log Wλ ∝ β log λLλ(1450 Å), shows a tendency to become steeper toward higher luminosity. The slope of the Baldwin effect also increases with the ionization energy needed to create the individual lines. In contrast to this general trend, the N V λ1240 equivalent width is nearly independent of continuum luminosity and remains nearly constant. The overall line behaviors are consistent with softer UV continuum shapes and perhaps increasing gas metallicity in more luminous active galactic nuclei.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/774aeea472193242e62dab09b97c180684563268

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Citations in the corpus

The evolution of the broad-line region among SDSS quasars (2005, methodology): “Our analysis on the composite spectra shows that there is no apparent dependence of emission-line flux ratios on redshift up to z ∼ 4.5, which is consistent with the results of Dietrich et al. (2002).”
UNIFICATION OF LUMINOUS TYPE 1 QUASARS THROUGH C iv EMISSION (2010, methodology): “Support for this interpretation comes from evidence that the effect disappears when referenced to the ionizing luminosity instead of the UV luminosity (Green 1996) and that there is an observed dependence on ionization potential (e.g., Dietrich et al. 2002).”
ANALYSIS OF OPTICAL Fe ii EMISSION IN A SAMPLE OF ACTIVE GALACTIC NUCLEUS SPECTRA (2010, background): “On the other hand, no Baldwin effect has been noticed for the optical Fe ii and Hβ lines (Dietrich et al. 2002), or even an inverse Baldwin Effect has been reported: Croom et al. (2002) found an inverse Baldwin effect in Hβ and Netzer & Trakhtenbrot (2007) found one for both Hβ and optical Fe ii…”
Black Hole Masses and Eddington Ratios at 0.3 < z < 4 (2005, background): “This spectral index is the average spectral slope measured for the ∼700 AGNs of comparable luminosity in the sample of Dietrich et al. (2002).”
Early Growth and Efficient Accretion of Massive Black Holes at High Redshift (2003, background): “Thanks are due to Anca Constantin, Fred Hamann, Joe Shields, and Xiaohui Fan for providing the digital spectra of their z ≈ 4 quasars, Martin Elvis for providing a digital form of the average quasar SEDs, Dave Sanders for providing his Lbol measurements of the Palomar-Green quasars, and Adam Steed f”
Ultraviolet Detection of the Tidal Disruption of a Star by a Supermassive Black Hole (2006, background): “23 during the CFHTLS observations and power a broad Hb line with a luminosity of ergs s (Dietrich et al. 2002)41 11 # 10 at the time of the Keck spectrum, both of which are definitively ruled out by the observations.”
Hubble Space Telescope STIS Ultraviolet Spectral Evidence of Outflow in Extreme Narrow-Line Seyfert 1 Galaxies. II. Modeling and Interpretation (2004, background): “Neither IRAS 13224−3809 nor 1H 0707−495 show an especially strong Balmer jump (note that the Balmer jump can be distinguished from the strong Fe II by the wavelength of onset; e.g. Dietrich et al. 2002).”
A systematic search for changing-look quasars in SDSS (2015, background): “Since the Mg ii EW remains constant (leading to a negligible Baldwin effect, as seen for an ensemble of objects in Dietrich et al. 2002), it seems that the Mg ii BEL response in J0225+0030 is more pronounced than in typical AGN.”