Estimation of absolute magnitude-dependent Galactic model parameters in intermediate latitude with SDSS and SCUSS

Abstract

Based on the Sloan Digital Sky Survey and South Galactic Cap of u-band Sky Survey (SCUSS) early data, we use a star count method to estimate the Galactic structure parameters in an intermediate latitude with 10 180 main-sequence (MS) stars in an absolute magnitude interval of 4 ≤ Mr ≤ 13. We divide the absolute magnitude into five intervals, 4 ≤ Mr < 5, 5 ≤ Mr < 6, 6 ≤ Mr < 8, 8 ≤ Mr < 10 and 10 ≤ Mr ≤ 13, and estimate the Galactic structure parameters in each absolute magnitude interval to explore their possible variation with the absolute magnitude. Our study shows that the parameters depend on absolute magnitude. For the thin disc, the intrinsic faint MS stars have large local space density and they tend to stay close to the Galactic plane. A plausible explanation is that faint MS stars with long lifetime experience and long gravitational interaction time result in a short scaleheight. However, for the thick disc, the parameters show a complex trend with absolute magnitude, which may imply the complicated original of the thick disc. For the halo, the intrinsic faint MS stars have large local density and small axial ratio, which indicate a flattened inner halo and a more spherical outer halo.