科研之友
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摘要
Based on the Sloan Digital Sky Survey, we develop a new Monte-Carlo-based method to estimate the photometric metallicity distribution MDF) for stars in the Milky Way. Compared with other photometric calibration methods, this method enables a more reliable determination of the MDF, particularly at the metal-poor and metal-rich ends. We present a comparison of our new method with a previous polynomial-based approach and demonstrate its superiority. As an example, we apply this method to main-sequence stars with 0.2 < g-r < 0.6, 6 kpc < R < 9 kpc, and in different intervals in height above the plane, vertical bar Z vertical bar. The MDFs for the selected stars within two relatively local intervals (0.8 kpc < vertical bar Z vertical bar < 1.2 kpc, 1.5 kpc < vertical bar Z vertical bar < 2.5 kpc) can be well-fit by two Gaussians with peaks at [Fe/H] approximate to -0.6 and -1.2, respectively: one associated with the disk system and the other with the halo. The MDFs for the selected stars within two more distant intervals (3 kpc < vertical bar Z vertical bar < 5 kpc, 6 kpc < vertical bar Z vertical bar < 9 kpc) can be decomposed into three Gaussians with peaks at [Fe/H] approximate to -0.6, -1.4, and -1.9, respectively, where the two lower peaks may provide evidence for a two-component model of the halo: the inner halo and the outer halo. The number ratio between the disk component and halo component(s) decreases with vertical distance from the Galactic plane, which is consistent with the previous literature.
