WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI?

Journal Article · Mon Aug 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/736/2/86· OSTI ID:21578268

Xiaobo, Dong; Jianguo, Wang; Tinggui, Wang; Huiyuan, Wang; Hongyan, Zhou ^[1]; Ho, Luis C ^[2]; Xiaohui, Fan ^[3]

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1. Key Laboratory for Research in Galaxies and Cosmology, University of Sciences and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China)
2. The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States)
3. Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

We used a large, homogeneous sample of 4178 z {<=} 0.8 Seyfert 1 galaxies and QSOs selected from the Sloan Digital Sky Survey to investigate the strength of Fe II emission and its correlation with other emission lines and physical parameters of active galactic nuclei. We find that the strongest correlations of almost all the emission-line intensity ratios and equivalent widths (EWs) are with the Eddington ratio (L/L{sub Edd}), rather than with the continuum luminosity at 5100 A (L{sub 5100}) or black hole mass (M{sub BH}); the only exception is the EW of ultraviolet Fe II emission, which does not correlate at all with broad-line width, L{sub 5100}, M{sub BH}, or L/L{sub Edd}. By contrast, the intensity ratios of both the ultraviolet and optical Fe II emission to Mg II {lambda}2800 correlate quite strongly with L/L{sub Edd}. Interestingly, among all the emission lines in the near-UV and optical studied in this paper (including Mg II {lambda}2800, H{beta}, and [O III] {lambda}5007), the EW of narrow optical Fe II emission has the strongest correlation with L/L{sub Edd}. We hypothesize that the variation of the emission-line strength in active galaxies is regulated by L/L{sub Edd} because it governs the global distribution of the hydrogen column density of the clouds gravitationally bound in the line-emitting region, as well as its overall gas supply. The systematic dependence on L/L{sub Edd} must be corrected when using the Fe II/Mg II intensity ratio as a measure of the Fe/Mg abundance ratio to study the history of chemical evolution in QSO environments.

• OSTI ID: 21578268
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 736; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CORRELATIONS
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION
GALAXIES
GALAXY NUCLEI
IRON
METALS
QUASARS
RADIATIONS
SEYFERT GALAXIES
TRANSITION ELEMENTS
ULTRAVIOLET RADIATION