Model Chemical Evolution:

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Model Chemical Evolution
Starburst Environment
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Once upon a time

• Somewhat big bang started it all.
• Radiation domination
• Matter domination
• Matter gets clumpy stars and galaxies started
  forming

• 75 Hydrogen
• 25 Helium

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It continues

• Nitrogen, Oxygen, Carbon formed.
• More and more stars formed from the enriched gas
  present.
• It all gives more and more elements to the
  universe.

Modelling starburst chemical evolution

• Calculates thrown-out elements called yields

• Estimates how much of different elements exist.

• Has many parameters

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Our general model

• The model is simple
• Instantaneous burst only
• Some parameters Starforming efficiency,
  SNIa/SNII-rate, IMF, Infall parameters,
  burst-length, number of bursts.

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Recent Data and Yields

• Portinari et.al Stellar winds Type II
  supernovae.
• Van der Hoek et. al Intemerdiate mass star.
• Nomoto et. al. Supernovae Type Ia.

• Various different masses
• Different metallicities
• Interpolation necessary

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Example Burst
Parameters

• SNIa/SNII 0.15
• No infall
• Initial Metal 0.004
• Eff 0.15
• Salpeter IMF
• Six bursts, 2Gyr each.

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Standard vs General

• Comparison Olofssons standard model vs our
  general model.

Parameters

• No Infall
• No SNIa
• Initial Metal 0.004
• Eff 0.15
• Salpeter IMF
• One burst, 2Gyr

• Blue General
• Red Standard

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Blue Compact Galaxies
(Example of where our model applies)

• Dwarf-galaxies, dominated by a younger stellar
  population.
• Blue colors.
• High gas content and low metallicity
  (Z0.01-0.0004).
• Massive starbursts during usually no loger than
  100Myr
• Starburst environment, chemical evolution plays
  an important role.

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Observations - I
Parameters

• No Infall
• SNIa/SNII 0.15
• Initial Metal 0.004
• Eff 0.15
• Salpeter IMF
• Six bursts, 2Gyr each.

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Observations - II
Parameters

• No Infall
• SNIa/SNII 0.10
• Initial Metal 0.004
• Eff 0.15
• Salpeter IMF
• Six bursts, 2Gyr each.

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Why?

• Many possible parameters

• Matteucci et.al
• "Other parameters such as the number and
  duration of bursts, the effeiciency of the SF and
  the galactic wind, the slope of the IMF and the
  production of N, regarding it's primary or
  secondary origin in massive stars, were varied in
  order to understand the observed distribution of
  N/O, C/O, Si/O and O/Fe versus O/H in BCGs.

• (O/H) is pretty ok, N/O and C/O to high!

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Variable IMF
Parameters

• No Infall
• SNIa/SNII 0.15
• Initial Metal 0.004
• Eff 0.15
• Six bursts, 2Gyr each.
• Variable IMF

• Red x 1.35 (Salpeter)
• Blue x 0.35
• Green x 0

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Infall - Example
Parameters

• Non-zero Infall parameters
• SNIa/SNII 0.15
• Eff 0.15
• Two bursts, 2Gyr each.
• Salpeter IMF

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Supernovae Type Ia
Parameters

• No Infall
• SNIa/SNII variable
• Eff 0.15
• One burst, 2Gyr.
• Salpeter IMF

• Red Rate 0.15
• Blue Rate 0

15
Conclusions

• The result of the general model is surprisingly
  similar to the standard model, since only
  instantaneous bursts considered.
• Supernovae Type Ia and Infall seems reasonable.
• The abundance of O/H seems reasonable .
• The standard setup seems incomplete to reach the
  observed abundance-ratios in N/O and C/O.
• Possible alternations of parameters like IMF and
  SNIa/SNII-rate needs justification to fit
  observational data.
• Future work include fitting parameters and
  further applications and comparison with other
  type models.