Based on synthetic flux spectra calculated from theoretical atmospheric models, a calibration of temperature and metallicity for the dwarfs observed in the Beijing-Arizona-Taiwan-Connecticut multicolor photometric system is presented in this paper. According to this calibration, stellar effective temperatures can be obtained from some temperature-sensitive color indexes. The sample stars have colors and magnitudes in the ranges 0.1 < d - i < 0.9 and 14.0 < i < 20.5. The photometric metallicities for these sample stars can be derived by fitting SEDs. We determine the average stellar metallicity as a function of distance from the Galactic plane. The metallicity gradient is found to be d[Fe/H]/dz = -0.37 ± 0.1 dex kpc-1 for z < 4 kpc and d[Fe/H]/dz = -0.06 ± 0.09 dex kpc-1 between 5 and 15 kpc. These results can be explained in terms of different contributions in density distribution for Galactic model "thin disk," "thick disk," and "halo" components. However, for the gradient in z > 5 kpc, it could not be interpreted according to the different contributions from the three components because of the large uncertainty. So it is possible that there is little or no gradient for z > 5 kpc. The overall distribution shows a metallicity gradient d[Fe/H]/dz = -0.17 ± 0.04 dex kpc-1 for z < 15 kpc.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science