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تسجيل مستخدم جديدConstraining the Galactic structure parameters with the XSTPS-GAC and SDSS photometric surveys
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Photometric data from the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC) and the Sloan Digital Sky Survey (SDSS) are used to derive the global structure parameters of the smooth components of the Milky Way. The data, which cover nearly 11,000 deg$^2$ sky area and the full range of Galactic latitude, allow us to construct a globally representative Galactic model. The number density distribution of Galactic halo stars is fitted with an oblate spheroid that decays by power law. The best-fit yields an axis ratio and a power law index $kappa=0.65$ and $p=2.79$, respectively. The $r$-band differential star counts of three dwarf samples are then fitted with a Galactic model. The best-fit model yielded by a Markov Chain Monte Carlo analysis has thin and thick disk scale heights and lengths of $H_{1}=$ 322,pc and $L_{1}=$2343,pc, $H_{2}=$794,pc and $L_{2}=$3638,pc, a local thick-to-thin disk density ratio of $f_2=$11,per,cent, and a local density ratio of the oblate halo to the thin disk of $f_h=$0.16,per,cent. The measured star count distribution, which is in good agreement with the above model for most of the sky area, shows a number of statistically significant large scale overdensities, including some of the previously known substructures, such as the Virgo overdensity and the so-called north near structure, and a new feature between 150degr $< l < $ 240degr~and $-1$5degr $< b < $ $-$5degr, at an estimated distance between 1.0 and 1.5,kpc. The Galactic North-South asymmetry in the anticentre is even stronger than previously thought.
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