The effect of different type Ia supernova progenitors on Galactic chemical evolutionF. Matteucci1, 2, E. Spitoni1, S. Recchi3, and R. Valiante4
1 Dipartimento di Astronomia, Universitá di Trieste, via G. B. Tiepolo 11, 34143 Trieste, Italy
2 INAF Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34143 Trieste (TS), Italy
3 Institute of Astronomy, Vienna University, Türkenschanzstrasse 17, 1180, Vienna, Austria
4 Dipartimento di Astronomia, Universita di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy
Received 17 February 2009 / Accepted 7 April 2009
Aims. Our aim is to show how different hypotheses about type Ia supernova progenitors can affect Galactic chemical evolution. Supernovae Ia are believed to be the main producers of Fe and the timescale with which Fe is restored into the interstellar medium depends on the assumed supernova progenitor model. This is a way of selecting the most appropriate progenitor model for supernovae Ia, a still debated issue.
Methods. We include different type Ia SN progenitor models, identified by their distribution of time delays, in a very detailed chemical evolution model for the Milky Way which follows the evolution of several chemical species. We test the single degenerate and the double degenerate models for supernova Ia progenitors, as well as other more empirical models based on differences in the time delay distributions.
Results. We find that assuming the single degenerate or the double degenerate scenario produces negligible differences in the predicted [O/Fe] vs. [Fe/H] relation. On the other hand, assuming a percentage of prompt (exploding in the first 100 Myr) type Ia supernovae of 50%, or that the maximum type Ia rate is reached after 3–4 Gyr from the beginning of star formation, as suggested by several authors, produces more noticeable effects on the [O/Fe] trend. However, given the spread still existing in the observational data, no model can be firmly excluded on the basis of only the [O/Fe] ratios. On the other hand, when the predictions of the different models are compared with the G-dwarf metallicity distribution, the scenarios with very few prompt type Ia supernovae can be excluded.
Conclusions. Models including the single degenerate or double degenerate scenario with a percentage of 10–13% of prompt type Ia supernovae produce results in very good agreement with the observations. A fraction of prompt type Ia supernovae larger than 30% worsens the agreement with observations and the same occurs if no prompt type Ia supernovae are allowed. In particular, two empirical models for the type Ia SN progenitors can be excluded: the one without prompt type Ia supernovae and the one assuming a delay time distribution that is t-0.5. We conclude that the typical timescale for the Fe enrichment in the Milky Way is around 1–1.5 Gyr and that type Ia supernovae already should appear during the halo phase.
Key words: Galaxy: evolution -- stars: supernovae: general -- Galaxy: solar neighbourhood
© ESO 2009