The metallicity distributions in high-latitudes with SDSS

Abstract

We present metallicities and their variations with different parameters for 36 high-latitude fields covering Galactic longitudes 0° < l ⩽ 360°. The metallicities for relatively short vertical distances ( z < 2.5 kpc) show systematic fluctuations with Galactic longitude, similar to those of the thick-disc scaleheight, which may be interpreted as indicating a common origin, viz., the flare effect of the disc ( Bilir et al., 2007, MNRAS). This suggestion is supported by the metallicity variations which we find as functions of radial distance. The metallicity variation at larger vertical distances (6.5 < z ⩽ 9.5 kpc) is small but monotonic. Three different vertical metallicity gradients could be detected: d[ M/ H]/d z = − 0.22(±0.03), d[ M/ H]/d z = −0.38(±0.06), and d[ M/ H]/d z = −0.08(±0.07) dex kpc −1 for the intervals z < 3, 3 ⩽ z < 5, and 5 ⩽ z < 10 kpc, respectively. Since our data cover the whole Galactic longitude interval, the resulting metallicity gradients can be interpreted as properties of the larger-scale Galaxy. The first gradient confirms the dissipational formation of the disc at short z-distances. The steeper gradient corresponds to the transition region between different population components of the Galaxy, and finally, the lowest value provides an adequate description of the inner-halo metallicity gradient.