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Model Chemical Evolution:. Starburst Environment. 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. It continues…. Nitrogen, Oxygen, Carbon formed.

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model chemical evolution

Model Chemical Evolution:

Starburst Environment

once upon a time
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

it continues
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

our general model
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.
recent data and yields
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

example burst
Example Burst

Parameters

SNIa/SNII = 0.15

No infall

Initial Metal = 0.004

Eff = 0.15

Salpeter IMF

Six bursts, 2Gyr each.

standard vs general
Standard vs General

Comparison: Olofsson’s standard model vs our general model.

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

Parameters

Blue = General

Red = Standard

blue compact galaxies
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 (Z~0.01-0.0004).
  • Massive starbursts during usually no loger than 100Myr
  • Starburst environment, chemical evolution plays an important role.
observations i
Observations - I

Parameters

  • No Infall
  • SNIa/SNII = 0.15
  • Initial Metal = 0.004
  • Eff = 0.15
  • Salpeter IMF
  • Six bursts, 2Gyr each.
observations ii
Observations - II

Parameters

  • No Infall
  • SNIa/SNII = 0.10
  • Initial Metal = 0.004
  • Eff = 0.15
  • Salpeter IMF
  • Six bursts, 2Gyr each.
slide11
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!

variable imf
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

infall example
Infall - Example

Parameters

  • Non-zero Infall parameters
  • SNIa/SNII = 0.15
  • Eff = 0.15
  • Two bursts, 2Gyr each.
  • Salpeter IMF
supernovae type ia
Supernovae Type Ia

Parameters

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

Red : Rate = 0.15

Blue : Rate = 0

conclusions
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.

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