1. Metallicity Evolution of Active Galactic Nuclei
Tohru Nagao (National Astronomical Observatory of Japan)
Roberto Maiolino (INAF — Roma)
Alessandro Marconi (INAF — Arcetri)

2. Galaxies or AGNs ?? Why Metallicity? by focusing on …
~ 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)
by focusing on …
Galaxies or AGNs ??
◎ high number density × low
× rest-optical important lines ◎ rest-UV
× 0<z<3 (or less) target redshift ◎ 0<z<6 (or more)
× faint intrinsic luminosity ◎ bright

3. Composites at 2.0 < z < 2.5 Study on BLR metallicity
example:
Composites at 2.0 < z < 2.5
-24.5>MB> (643 QSOs)
-25.5>MB> (1497 QSOs)
-26.5>MB> (917 QSOs)
-27.5>MB> (105 QSOs)
-28.5>MB> (5 QSOs)
TN, AM, RM (2006a)
Rest Wavelength (A)
Study on BLR metallicity
SDSS-DR spectra
of 2.0<z<4.5
making Composite Spectra
for each (z, LAGN) bins
 very high S/N spectra

4. Dependences of emission-line flux ratios on (z, L)
Redshift
absolute B mag
TN, AM, RM (2006a)

5. ZBLR / Zsun ZBLR / Zsun Dependences of BLR metallicity on (z, L)
BLR metallicity is strongly correlated with AGN luminosity, but… NO redshift evolution up to z=4.5 !!
ZBLR / Zsun
TN, AM, RM (2006a)

6. NVl1240 / HeIIl1640 NVl1240 / CIVl1549 Study on NLR metallicity
DeBreuck et al. (2000)
2 < z < 5
Narrow-Line Radio Galaxies
BLR model
NLR model
NV emission from NLR
is generally VERY weak
Only upper limits on F(NV)
have been obtained for
most of radio galaxies…
Metallicity diagnostics
without NV emission
should be applied !!

7. NLR metallicity diagnostic
TN, RM, AM (2006b)
49 radio galaxies at 1.2 < z < 3.8
correlation: consistent to model
how depends on z and LAGN ??
CLOUDY calculations
one-zone, dust-free clouds
CIV/HeII : sensitive to ZNLR
CIII]/CIV : correction for U

8. 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 1.2<z<3.8

9. galaxies AGNs Why no metallicity evolution? z=0 Metallicity z=2
Galaxy Mass
z=0
z=2
Erb et al.
(2006)
redshift
evolution
galaxies
AGNs
NV/HeII NV/CIV
absolute B mag
TN, AM, RM (2006a)
INCONSISTENT !?
a possible interpretation:
SDSS QSOs are too bright
 host galaxies are too massive
 Z evolution has been completed
Metallicity studies on
high-z low-luminous AGNs
are crucially important !!

10. Summary
BLR metallicity
Composite spectra of 5344 SDSS quasars
Correlations with LAGN: non-correlations with z
NV/CIV, NV/HeII, (SiIV+OIV])/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 < z < 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

11. Appendix

13. Photoionization Model
Calculations