Neutral Gas

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Neutral Gas Metals from z4 to z0.5

• Céline Péroux(European Southern
  ObservatoryGermany)

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PLAN

• What are quasar absorbers?
• Evolution of the neutral gas mass
• The missing metals problem
• Absorbers as tracers of global metallicity

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PLAN

• What are quasar absorbers?
• Evolution of the neutral gas mass
• The missing metals problem
• Absorbers as tracers of global metallicity

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What are Quasar Absorbers?
Neutral gas HI -gt molecular hydrogen H2 -gt star
formation
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Damped Lyman-? Absorbers
log N(HI)gt20.3 cm-2

• Seen at all z
• Selected regardless of luminosity, morphology,
  star formation rate
• Physical properties well constrained N(HI),
  metals, molecules, etc.
• Major component of neutral gas
• Tracers of global metallicity

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Voigt Profile Fitting
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PLAN

• What are quasar absorbers?
• Evolution of the neutral gas mass
• The missing metals problem
• Absorbers as tracers of global metallicity

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Neutral Gas in the Universe
STARS
NEUTRAL GAS
LOCAL GALAXIES
?HI(zlt2) poorly constrained
(Péroux, Dessauges, D'Odorico, Kim McMahon,
2005, MNRAS, 363, 479)
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PLAN

• What are quasar absorbers?
• Evolution of the neutral gas mass
• The missing metals problem
• Absorbers as tracers of global metallicity

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Expected Metal Production

• Star Formation History
• Product of mean stellar yield times integral of
  star formation density
• ?expltpgt? ?(t)

Expected metals
(Madau plot)
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Missing Metals Problem
z2.5
expected metals
?
metals
DLAs

• Observed metals 60 of expected metals

galaxies
Intergalactic medium
(Bouché, Lehnert Péroux, 2005, MNRAS, 364, 319
Bouché, Lehnert Péroux, 2006, MNRAS, 367L, 16
Bouché, Lehnert, Aguirre, Péroux Bergeron,
submitted)
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PLAN

• What are quasar absorbers?
• Evolution of the neutral gas mass
• The missing metals problem
• Absorbers as tracers of global metallicity

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Accurate Metallicity Measurements

• UVES/VLT ESO archives
• Zn traces total metallicity free from dust bias

(Péroux, Dessauges, D'Odorico, Kim McMahon,
2003b, MNRAS, 346, 1103)
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Metallicity versus N(HI)

• Sub-DLAs more metal rich?

(Péroux, Dessauges, D'Odorico, Kim McMahon,
2003b, MNRAS, 345, 480)
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Metallicity of sub-DLAs

• UVES/VLT
• abundances zgt3 sub-DLAs

(Péroux, Dessauges, D'Odorico, Kim McMahon, in
preparation)
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Metallicity of sub-DLAs

• measure Zn at zlt1
• ESO DDT
• Zn/H0.61
• super-solar quasar absorber

(Péroux, Meiring, Kulkarni, Ferlet, Khare,
Lauroesch, Vladilo York, 2006b, MNRAS, )
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A Metal-Rich Quasar Absorber

• Sub-DLAs better tracers of global metallicity?
• Mass difference?Obs bias?

(Péroux, Kulkarni, Meiring, Ferlet, Khare,
Lauroesch, Vladilo York, 2006a, AA, 450, 53)
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Dust Bias

• Extinction in HI regions in the Milky Way

(Vladilo Péroux, 2005, AA, 444, 461)
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Overcoming Dust Bias

• Need to probe lower HI column densities
  down to N(HI)gt1019 gt
  sub-DLAs

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Contribution of Absorbers to Missing Metals
Problem (z2.5)

• DLAs 5 of total amount of metals
• Neutral gas in sub-DLAs 1.3gt because
  contribution to ?HI small
• Ionised gas in sub-DLAs max of 13gt not
  enough to close missing metals problem

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Conclusion

• Quasar absorbers trace the HI from which stars
  form
• Most of the metals expected in the Universe are
  missing
• Quasar absorbers are a cosmological tool allowing
  accurate metallicity determination
• Sub-DLAs might be more metal rich than classical
  DLAs, possibly because of a lower dust content