Context :

Aims : In order to verify the effects of the most recent data on the evolution of Carina and Sagittarius Dwarf Spheroidal Galaxies ( dSph ) and to set tight constraints on the main parameters of chemical evolution models , we study in detail the chemical evolution of these galaxies through comparisons between the new data and the predictions of a model , already tested to reproduce the main observational constraints in dSphs .

Methods : Several abundance ratios , such as [ \alpha /Fe ] , [ Ba/Fe ] and [ Eu/Fe ] , and the metallicity distribution of stars are compared to the predictions of our models adopting the observationally derived star formation histories in these galaxies .

Results : These new comparisons confirm our previously suggested scenario for the evolution of these galaxies , and allow us to better fix the star formation and wind parameters .
In particular , for Carina our predictions indicates that the best efficiency of star formation is \nu = 0.15 Gyr ^ { -1 } , that the best wind efficiency parameter is w _ { i } = 5 ( the wind rate is five times stronger than the star formation rate ) , and that the star formation history , which produces the best fit to the observed metallicity distribution of stars is characterized by several episodes of activity .
In the case of Sagittarius our results suggest that \nu = 3 Gyr ^ { -1 } and w _ { i } = 9 , again in agreement with our previous work .
Finally , we show new predictions for [ N/Fe ] and [ C/Fe ] ratios for the two galaxies suggesting a scenario for Sagittarius very similar to the one of the solar vicinity in the Milky Way , except for a slight decrease of [ N/Fe ] ratio at high metallicities due to the galactic wind .
For Carina we predict a larger [ N/Fe ] ratio at low metallicities , reflecting the lower star formation efficiency of this galaxy relative to Sagittarius and the Milky Way .

Conclusions :