Metallicity distribution predicted by our chemical evolution model indicated by the red histogram. The observed distribution calculated including both high-α and low-α stars is shown by the black, empty histogram. The cyan line indicates the metallicity distribution of our chemical evolution model convolved with a Gaussian with standard deviation σ = 0.13 dex. Finally, the purple line indicates the metallicity distribution of our chemical evolution model convolved with a Gaussian with standard deviation σ = 0.07 dex.