Determination of Abundances of Chemical Elements in the Cosmos

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Determination of Abundances of Chemical Elements
in the Cosmos
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Why Are Abundances Important?

• Natural history of the elements
• Rate of element production in stars
• Levels of biologically important elements
• Stellar evolution

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Top 10 elements in the universe body
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Stellar Evolution
Gas pressure outward
Gravity inward
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Examples of Stellar Nucleosynthesis Reactions
4 1H --gt 4He 3 4He --gt 12C 12C 4He --gt 16O 16O
4He --gt 20Ne 20Ne 4He --gt 24Mg
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SN 1987A 2/23/87
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Galactic Chemical Evolution
The conversion of H, He into metals over time
heavy elements metals all elements besides H
and He
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CHEMICAL EVOLUTION OF A GALAXY
Stars produce heavy elements Stars expel
products into the interstellar medium
INTERSTELLAR MEDIUM
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stellar evolution
star death
star birth
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Results of Galactic Chemical Evolution

• 1. INTERSTELLAR MEDIUM BECOMES RICHER IN HEAVY
  ELEMENTS
• NEXT STELLAR GENERATION
• CONTAINS MORE HEAVY ELEMENTS

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Heavy element abundances
Time
Age-Metallicity Relation
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Checking the Hypotheses

• Measure abundances
• Compare with predictions

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Measuring Abundances Spectra

• Emission spectrum
• Absorption spectrum

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The Physics of Emission Lines

• Bound-bound transition
• Inelastic ion-e- collision
• Radiative deexcitation
• Photon production
• Inelastic collision

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Emission Spectrum
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DdDm-1 Abundances from an emission spectrum

• Planetary nebula
• Remnant of an evolved star
• Located in the halo of the MWG
• Distance 37,000 ly

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Why Study DdDm-1?

• Learn about element production in a solar type
  star
• Learn about halo formation and evolution in the
  Milky Way

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Data Gathering
Ultraviolet Hubble
Visible 2.1m KPNO
Infrared Spitzer
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Calculating Abundances from Emission Lines
Abundance Software
Measure
Publish
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Our Conclusions for DdDm-1

• C abundance less than expected
• O and Fe abundances consistent with halo location

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The Physics of Absorption Lines

• Bound-bound transition
• Photoexcitation of e-
• Radiative deexcitation
• Photon production
• Photon scattered

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Absorption Spectrum
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Damped Ly-? Systems Abundances from an
absorption spectrum

• Galaxy between a quasar and earth
• High redshift
• Early universe objects

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Why Study DLAs?

• Abundances in the early universe
• Stellar element production at low metallicities

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Data Gathering
Keck Observatory
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Calculating Abundances from Absorption Lines
Abundance Software
Measure
Publish
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Observations
Models
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Our Conclusions for DLAs

• S and Si increase in lockstep
• DLAs have low star formation rates

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ASTRONOMY AT
Bill Romanishin Solar system
Eddie Baron Supernova studies
David Branch Supernova studies
Karen Leighly Active Galactic nuclei
John Cowan Chemical evolution Milky Way
studies Supernova remnants
Yun Wang Cosmology Dark matter Dark energy
Dick Henry Chemical evolution Galaxies Nebular
abundances