Based on SDSS g , r and SCUSS ( South Galactic Cap of u-band Sky Survey ) u photometry , we develop a photometric calibration for estimating the stellar metallicity from u - g and g - r colors by using the SDSS spectra of 32,542 F- and G-type main sequence stars , which cover almost 3700 deg ^ { 2 } in the south Galactic cap .
The rms scatter of the photometric metallicity residuals relative to spectrum-based metallicity is 0.14 dex when g - r < 0.4 , and 0.16 dex when g - r > 0.4 .
Due to the deeper and more accurate magnitude of SCUSS u band , the estimate can be used up to the faint magnitude of g = 21 .
This application range of photometric metallicity calibration is wide enough so that it can be used to study metallicity distribution of distant stars .
In this study , we select the Sagittarius ( Sgr ) stream and its neighboring field halo stars in south Galactic cap to study their metallicity distribution .
We find that the Sgr stream at the cylindrical Galactocentric coordinate of R \sim 19 kpc , \left|z \right| \sim 14 kpc exhibits a relative rich metallicity distribution , and the neighboring field halo stars in our studied fields can be modeled by two-Gaussian model , with peaks respectively at [ Fe/H ] = -1.9 and [ Fe/H ] = -1.5 .