Uncertainties in Galactic Chemical Evolution Models

Côté, B. and Ritter, C. h. and O'Shea, B. W. and Herwig, F. and Pignatari, Marco (2016) Uncertainties in Galactic Chemical Evolution Models. ASTROPHYSICAL JOURNAL, 824 (2). ISSN 1538-4357

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Abstract

We use a simple one-zone galactic chemical evolution model to quantify the uncertainties generated by the input parameters in numerical predictions, for a galaxy with properties similar to those of the Milky Way. We compiled several studies from the literature to gather the current constraints for our simulations regarding the typical value and uncertainty of seven basic parameters, which are: the lower and upper mass limit of the stellar initial mass function (IMF), the slope of the high-mass end of the stellar IMF, the slope of the delay-time distribution function of Type Ia supernovae (SNe Ia), the number of SNe Ia per solar mass formed, the total stellar mass formed, and the initial mass of gas of the galaxy. We derived a probability distribution function to express the range of likely values for every parameter, which were then included in a Monte Carlo code to run several hundred simulations with randomly selected input parameters. This approach enables us to analyze the predicted chemical evolution of 16 elements in a statistical way by identifying the most probable solutions along with their 68% and 95% confidence levels. Our results show that the overall uncertainties are shaped by several input parameters that individually contribute at different metallicities, and thus at different galactic ages. The level of uncertainty then depends on the metallicity and is different from one element to another. Among the seven input parameters considered in this work, the slope of the IMF and the number of SNe Ia are currently the two main sources of uncertainty, whereas the lower and upper mass limit of the IMF do not play a significant role. On average, the overall uncertainty ranges between 0.1 to 0.5 dex at a given metallicity. The confidence levels can reach values above 1 dex when looking at the evolution of individual elements as a function of galactic age, instead of metallicity.

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