Metallicities and Abundance Ratios from Quasar Broad Emission Lines

By F. Hamann, K. Korista, G. Ferland, C. Warner, J. Baldwin. 2001

141 citations recorded by the source corpus.

The broad emission lines (BELs) of quasars and active galactic nuclei (AGNs) are important diagnostics of the relative abundances and overall metallicity in the gas. Here we present new theoretical predictions for several UV BELs. We focus specifically on the relative nitrogen abundance as a metallicity indicator, based on the expected secondary enrichment of nitrogen at metallicities Z ≳ 0.2 Z☉. Among the lines we consider, N III] λ1750/O III] λ1664, N V λ1240/(C IV λ1549 + O VI λ1034), and N V/He II λ1640 are the most robust diagnostics. We argue, in particular, that the average N V BEL is not dominated by scattered Lyα photons from a broad absorption-line wind. We then compare our calculated line ratios with observations from the literature. The results support earlier claims that the gas-phase metallicities near quasars are typically near or several times above the solar value. We conclude that quasar activity is preceded by, or coeval with, an episode of rapid and extensive star formation in the surrounding galactic (or protogalactic) nuclei. Chemical evolution models of these environments suggest that, to reach Z ≳ Z☉ in well-mixed interstellar gas, the star formation must have begun ≳108 yr before the observed quasar activity.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5415ee39ef1d31e3dd9c6f2c0d58abbd7b64bc0f

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Citations in the corpus

Near-Infrared Spectroscopy of High-Redshift Active Galactic Nuclei. I. A Metallicity-Accretion Rate Relationship (2004, methodology): “Using a grid of photoionization calculations, performed with the locally optimally emitting cloud model (LOC; e.g., Baldwin et al. 1995), Hamann et al. (2002) found that N v/C iv can trace the BLR gas metallicity, and it only weakly depends on the chosen SED and density.”
Continuum and Emission-Line Strength Relations for a Large Active Galactic Nuclei Sample (2002, unknown): “/ O=H; see Hamann et al. 2002).”
THE QUASAR OUTFLOW CONTRIBUTION TO AGN FEEDBACK: VLT MEASUREMENTS OF SDSS J0318-0600 (2009, methodology): “With this in mind Hamann et al. (2001, 2002) constructed a simple piece-wise power law radio-quiet quasar SED to model intrinsic AGN absorption systems and broad emission lines.”
Emission-line diagnostics of low-metallicity active galactic nuclei (2006, background): “The results for both high and low redshift AGN appear to show that most AGN have solar to supersolar metallicities (Storchi-Bergmannet al. 1998; Hamann et al. 2002).”
Hubble Space Telescope STIS Ultraviolet Spectral Evidence of Outflow in Extreme Narrow-Line Seyfert 1 Galaxies. II. Modeling and Interpretation (2004, background): “In this case, we also increased the nitrogen abundance to 10 times the solar value to better match the observed N V. Selective enhancement of nitrogen is justified on the basis of secondary enrichment processes that may be important in AGN (e.g., Hamann et al. 2002).”
BLACK HOLE MASS ESTIMATES AND EMISSION-LINE PROPERTIES OF A SAMPLE OF REDSHIFT z > 6.5 QUASARS (2013, methodology): “In particular, Hamann et al. (2002) showed that the most robust abundance probes are N iii]/O iii], N v/(C iv+O iv), and N v/He ii.”
X-shooter reveals powerful outflows in z ∼ 1.5 X-ray selected obscured quasi-stellar objects (2014, background): “…that Broad Absorption Line Quasars (BAL QSOs, e.g. Dunn et al. 2010) may be objects in the transition phase between the ULIRGs and unobscured QSO phase, where the outflowing wind in the ionized component is seen directly in optical-UV spectra (e.g., de Kool et al. 2001; Hamann et al. 2002).”
The evolution of the broad-line region among SDSS quasars (2005, methodology): “Our results are almost consistent with those of Hamann et al. (2002).”
Cosmic Evolution of Mass Accretion Rate and Metallicity in Active Galactic Nuclei (2006, methodology): “As shown in S04, the N/C abundance (and metalicity in general) as measured from the N V λ1240/CIV λ1549 line ratio (Hamann et al. 2002 and references therein) is strongly correlated withL/LEdd over a large luminosity range.”
Broad iron L line and X-ray reverberation in 1H0707-495 (2009, background): “The high iron abundance (∼ 9× solar), if real, is not inconsistent with what is expected from line ratio modeling at other wavelengths (Shemmer & Netzer 2002; Hamann et al. 2002), and would imply that the host galaxy had gone through a phase of strong star formation.”
Gemini Near-Infrared Spectroscopy of Luminous z ∼ 6 Quasars: Chemical Abundances, Black Hole Masses, and Mg II Absorption (2007, methodology): “We estimate the metallicity from the N v/C iv and N v/He ii ratios using Figure 5 of Hamann et al. (2002).”
EVIDENCE FOR NON-EVOLVING Fe ii/Mg ii RATIOS IN RAPIDLY ACCRETING z ∼ 6 QSOs (2011, background): “Regarding the chemical enrichment, photoionization models show that various emission line ratios are good estimators for the metallicity of the BLR gas (e.g. Hamann et al. 2002; Nagao et al. 2006).”