The Study Of Galaxy Stream

The star stream is a globular cluster or dwarf galaxy that is gradually deformed,disintegrated,and torn apart by the massive tidal action of the gravitational attraction of the galaxy.The star stream is a prediction of galaxy model formation and is one of the hot issues in astrophysics research.In this master thesis,based on a large number of stellar spectral data obtained from the LAMOST spectrum survey,to study and discuss the dynamics and chemical abundance of Sagittarius dwarf galaxies.This gives us a better understanding of the evolution,of Sagittarius(Sgr)dwarf galaxies and the structure of the Milky Way.The LAMOST DR3 provided 341691 K giant stars with stellar parameters for us.First,we selected K giant stars belong to the Sagittarius dwarf galaxies as sample stars.The Law&Majewski et al.(2010)and Belokurov et al.(2014)give the models that select the K giant stars belong to Sagittarius dwarf galaxies.We used the model to select the K giant stars and obtained 456 and 138 K giant stars belong to the leading stream and trailing stream.Then using these stars we studied the chemical abundance of Sagittarius dwarf galaxies.We studied metallicity distribution of member stars along the streams and found a flat gradient in the first wrap of leading stream,in the second wrap of leading stream and in the first wrap of trailing stream we obtained the gradient-(0.88±0.3)×10-3der degree-1 and-(1.2±0.3)×10-3deax degree-1,respectively.At the same time,based on Shi et al.(2010),Chou et al.(2007),Monaco et al.(2005),Keller et al.(2010)and Monaco et al.(2007),we obtained some stellar data of Sagittarius dwarf galaxy.And that gives us a much wider range of star data.By using the K giant star data and the above work,we give a combined metallicity gradient value of the Sagittarius dwarf galaxy?Finally,we tried to analyze the characteristics of an overdensity in the Leading arm of a dwarf galaxy in Sagittarius and give the discussion of contamination of halo stars and the motion of Sgr streams?...