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Title: WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI?

Abstract

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 ofmore » 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.« less

Authors:
; ; ; ;  [1];  [2];  [3];  [4]
  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)
  4. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
Publication Date:
OSTI Identifier:
21578268
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 736; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/736/2/86; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CORRELATIONS; EMISSION; GALAXY NUCLEI; IRON; QUASARS; SEYFERT GALAXIES; ULTRAVIOLET RADIATION; COSMIC RADIO SOURCES; ELECTROMAGNETIC RADIATION; ELEMENTS; GALAXIES; METALS; RADIATIONS; TRANSITION ELEMENTS

Citation Formats

Dong Xiaobo, Wang Jianguo, Wang Tinggui, Wang Huiyuan, Zhou Hongyan, Ho, Luis C., Fan Xiaohui, and Yuan Weimin, E-mail: xbdong@ustc.edu.cn, E-mail: lho@obs.carnegiescience.edu, E-mail: wmy@nao.cas.cn, E-mail: wangjg@ynao.ac.cn, E-mail: fan@as.arizona.edu. WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI?. United States: N. p., 2011. Web. doi:10.1088/0004-637X/736/2/86.
Dong Xiaobo, Wang Jianguo, Wang Tinggui, Wang Huiyuan, Zhou Hongyan, Ho, Luis C., Fan Xiaohui, & Yuan Weimin, E-mail: xbdong@ustc.edu.cn, E-mail: lho@obs.carnegiescience.edu, E-mail: wmy@nao.cas.cn, E-mail: wangjg@ynao.ac.cn, E-mail: fan@as.arizona.edu. WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI?. United States. doi:10.1088/0004-637X/736/2/86.
Dong Xiaobo, Wang Jianguo, Wang Tinggui, Wang Huiyuan, Zhou Hongyan, Ho, Luis C., Fan Xiaohui, and Yuan Weimin, E-mail: xbdong@ustc.edu.cn, E-mail: lho@obs.carnegiescience.edu, E-mail: wmy@nao.cas.cn, E-mail: wangjg@ynao.ac.cn, E-mail: fan@as.arizona.edu. Mon . "WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI?". United States. doi:10.1088/0004-637X/736/2/86.
@article{osti_21578268,
title = {WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI?},
author = {Dong Xiaobo and Wang Jianguo and Wang Tinggui and Wang Huiyuan and Zhou Hongyan and Ho, Luis C. and Fan Xiaohui and Yuan Weimin, E-mail: xbdong@ustc.edu.cn, E-mail: lho@obs.carnegiescience.edu, E-mail: wmy@nao.cas.cn, E-mail: wangjg@ynao.ac.cn, E-mail: fan@as.arizona.edu},
abstractNote = {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.},
doi = {10.1088/0004-637X/736/2/86},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 736,
place = {United States},
year = {2011},
month = {8}
}