Metallicity Evolution of Active Galactic Nuclei

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Metallicity Evolution of Active Galactic Nuclei
Tohru Nagao (National Astronomical Observatory
of Japan) Roberto Maiolino (INAF
Roma) Alessandro Marconi (INAF Arcetri)
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Why Metallicity?
heavy elements ? SNe of massive stars,
mass-loss from less-massive stars imprint of
past star-formation history in each (host)
galaxy metallicity evolution ? star-formation /
metal-production history of the universe
investigating metallicity as a function of the
age of the universe ( redshift)
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Study on BLR metallicity
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Dependences of emission-line flux ratios on (z, L)
Redshift
absolute B mag
TN, AM, RM (2006a)
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Dependences of BLR metallicity on (z, L)
ZBLR / Zsun
BLR metallicity is strongly correlated with AGN
luminosity, but NO redshift evolution up to
z4.5 !!
ZBLR / Zsun
TN, AM, RM (2006a)
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Study on NLR metallicity
NV emission from NLR is generally VERY weak
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NLR metallicity diagnostic
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Dependences of NLR metallicity on (z, L)
TN, RM, AM (2006b)
Not only BLR, the NLR metallicity also depends on
LAGN but does not show any redshift evolution at
1.2ltzlt3.8
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Why no metallicity evolution?
Metallicity studies on high-z low-luminous
AGNs are crucially important !!
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Summary
BLR metallicity
Composite spectra of 5344 SDSS quasars Correlation
s with LAGN non-correlations with z NV/CIV,
NV/HeII, (SiIVOIV)/CIV, AlIII/CIV,
etc. LAGN-ZBLR relation does not show z-evolution
up to z 4.5
NLR metallicity
Compiled data of 49 narrow-line radio galaxies at
1.2 lt z lt 3.8 Correlations with LAGN
non-correlations with z new metal diagnostic
CIV/HeII with U-corrector CIII/CIV LAGN-ZNLR
relation does not show z-evolution up to z 3.8
Possible interpretation
Main star-formation activities in host galaxies
of bright AGNs might be already completed even at
z 4 ? studies on lower-LAGN / higher-z
AGNs are important
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Appendix
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Photoionization Model Calculations
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