Jonay Isa Gonzlez Hernndez

1
Galactic chemical evolution of oxygen in the
light of 3D stellar atmospheres

• Jonay Isaí González Hernández
• Observatoire de Paris-Meudon (GEPI)?
• Cosmological Impact of the First Stars
• (CIFIST Marie Curie Excellence Team)?

2
Outline

• Introduction
• Grid of 3D models
• Observations
• Analysis
• Preliminary results
• Conclussions

3
Oxygen

• The most abundant element
• after H and He
• Produced during
• hydrostatic and
• explosive
• nucleosynthesis
• in massive stars

Tominaga et al. (2007)?
4
Oxygen

• Its abundance is determined by
• - Forbidden lines OI 6300 and 6363 A
• - permitted near-IR triplet OI 7772-5 A
• - near-IR vibration-rotation bands
• - near-UV electronic transition bands

5
Oxygen in the Sun 3D

• Previous abundance determination
• log N(O)/N(H)128.66 (Asplund et al. 2005)?
• New abundance determination
• log N(O)/N(H)128.76 (Caffau et al. 2008)?

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Oxygen problem OI
Cayrel et al. (2004)?

• Each O abundance indicator provides a
• different abundance trend O vs. Fe
• OI shows a quasi-plateau with
• O/Fe0.4-0.5 in subgiants and giants
• (García Pérez et al. 2006 Cayrel et al.
  2004)?
• in the metallicity range -1.5 lt Fe/H lt -3.5
  
• However, from OI, Nissen et al. (2002)
• showed a linear increase O/Fe vs Fe/H in
• dwarfs in the range -0.5 lt Fe/H lt -2.5

Nissen et al. (2002)?
García Pérez et al. (2006)?
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Oxygen problem OI

• Near-IR OI triplet shows a linear steep
• increase O/Fe towards lower Fe/H
• (Israelian et al. 2001 Boesgaard et al 1999
• Nissen et al. 2002 Fulbright Johnson
• 2003) for dwarfs, subgiants and giants for
• -0.8 lt Fe/H lt -3.2
• Fulbright Johnson (2003) found a
• disagreement of 0.4 dex between OI triplet
• and OI

Israelian et al. (2001)?
8
Oxygen problem OH

• Near-UV OH shows also a linear steep
• increase of O/Fe towards lower Fe/H
• (Israelian et al. 2001 Boesgaard et al 1999)?
• for dwarfs with -0.8 lt Fe/H lt -3.4
• However, García Pérez et al. (2006) claimed
• a plateau of O/Fe0.5 for subgiants with
• -1.5 lt Fe/H lt -3.

García Pérez et al. (2006)?
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Oxygen problem

• It is clear that this disagreement should
• be related to the limitations of the
• analysis employed
• The deviations from NLTE and the effects
• of granulation and temperature
• inhomogeneities (3D effects) may help
• to solve this discrepancy

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Oxygen in metal-poor stars 1D
O/Fe
Fulbright Johnson (2003)?
Fe/H
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Oxygen in metal-poor starsNLTE and 3D effects

• OI is not sensitive to NLTE effects but
• is slightly affected by 3D inhomogeneities
• OI triplet is significantly dependent on
• NLTE effects
• Near-UV OH are strongly sensitive to
• 3D effects and maybe slightly dependent
• on NLTE although in the opposite direction

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Abundance trends Oxygen 3D
O/Fe
The most metal-poor spectroscopic binary dwarfs
CS22876-032 (Fe/H-3.7) González Hernández et
al. (2008)?
1D
dwarfs
3D
FeI/H
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3D model atmospheres

• 3D atmospheric models
• are computed with
• CO5BOLD (Wedemeyer et
• al. 2003)?
• Representative selection of
• snapshots of the stellar
• photosphere
• Spectral synthesis code
• Linfor3D

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Abundance corrections

• 3D - lt3Dgt corrections
• - lt3Dgt model temporal and
• horizontal average of the 3D model
• - Same micro-physics with vturb fixed
• 3D 1D corrections
• - Lagrangian hydrostatic 1D model
• - Same micro-physics with vturb fixed

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Model Atmospheres 3D
3D

• 3D versus 1D

OH
1D
Fe
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Model Atmospheres 3D

• 3D versus lt3Dgt
• lt3Dgt versus 1D

OH
Fe
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3D model grid
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3D Model gravity dependence
Fe/H-3
Teff5500 K
OH
Fe
19
3D Model Metallicity dependence
20
Observations

• Spectroscopy with VLT/UVES
• Spectral region 300.0-390.0 nm
• ?/d? 43,000
• S/N gt 100 at 312.0 nm

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Stellar parameters

• Teff from IRFM using 2MASS JHKs
• log g from Hipparcos paralaxes

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3D-1D abundance correctionTeff dependence
OH
23
3D-1D abundance correctionTeff dependence
Fe
24
3D-1D abundance correctionlog g dependence
OH
25
3D-1D abundance correctionexcitation potential
dependence
Fe
26
3D-1D abundance correctionexcitation potential
dependence
OH
27
1D O abundances
28
3D O abundances
29
Galactic oxygen evolution
Kobayashi et al. (2006)?
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Conclusions and Future work

• 3D models appear necessary in order to determine
  O abundances
• from near-UV OH bands, mainly due to cooling
  effects that
• metal-poor 3D models show
• The abudance trend of O seems to show a
  quasi-linear increase
• towards lower metallicity or at least two
  plateau, one at 0.5-0.6
• dex and the other at 0.9-1 dex at the lower
  metallicities.
• However, this might be considered with caution
  until 3D
• corrections and NLTE effects are applied to O
  and Fe for different
• abundance indicators in dwarfs, subgiants and
  giants

31
Galactic chemical evolution of oxygen in the
light of 3D stellar atmospheres

• Jonay Isaí González Hernández
• Observatoire de Paris-Meudon (GEPI)?
• Cosmological Impact of the First Stars
• (CIFIST Marie Curie Excellence Team)?

32
3D Model Metallicity dependence
33
Chemical Analysis

• FeI and FeII abundances (6500K) 1D

FeI
FeII
FeI
FeII
34
Chemical Analysis

• FeI and FeII abundances (6500) lt3Dgt

FeI
FeII
FeI
FeII
35
Abundance trends Oxygen 1D
O/FeI
OH
dwarfs
3D
3D
FeI/H
36
Abundance trends Oxygen 3D
O/Fe
dwarfs
FeI/H
37
Abundance trends Oxygen 3D
O/Fe
OI
giants
subgiants
dwarfs
FeI/H