The stellar metallicity distribution of the Milky Way from the Beijing-Arizona-Taiwan-Connecticut survey

Using the stellar atmospheric parameters such as effective temperature and metallicity derived from Sloan Digital Sky Survey spectra (SDSS) for similar to 2200 main sequence (MS) stars which were also observed by Beijing-Arizona-Taiwan-Connecticut (BATC) photometric system, we develop the polynomial photometric calibration method to evaluate the stellar effective temperature and metallicity for BATC multicolour photometric data. This calibration method has been applied to about 160 000 MS stars from 67 BATC observed fields. Those stars have colours and magnitudes in the ranges 0.1 < d - h < 1.4 and 14.0 < d < 21.0. We find that there is a peak of metallicity distribution at [Fe/H] similar to -1.5 in the distance from the Galactic plane vertical bar Z vertical bar > 5 kpc which corresponds to the halo component and a peak at [Fe/H] similar to -0.7 in the region 2 < vertical bar Z vertical bar < 5 kpc which is dominated by the thick disc stars. The mean stellar metallicity smoothly decreases from -0.65 to -0.78 in the interval 0.5 < vertical bar Z vertical bar < 2 kpc. Metallicity distributions in the halo and the thick disc seem invariant with the distance from the Galactic plane.