SDSS-DR7 red HB stars spectroscopic data

The trailing arm is composed mainly of a metal-rich component and [{alpha}/Fe] is obviously lower than that of the Galactic stars. The metallicity gradient is -(1.8+/-0.3)x10^-3^dex/deg in the first wrap of the trailing arm and -(1.5+/-0.4)x10^-3^dex/deg in the first wrap of the leading arm. No significant gradient exists along the second wraps of the leading or trailing arms.

It seems that the Sgr dwarf galaxy initially lost the metal-poor component in the second wrap (older) arms due to the tidal force of our Galaxy and then the metal-rich component is disrupted in the first wrap (younger) arms. Finally, we found that the velocity dispersion of the trailing arm from 88{deg}<{Lambda}_{sun}_<112{deg} is {sigma}=9.808+/-1.0km/s, which is consistent with previous work in the literature.