Member stars of the GD-1 tidal stream

With the photometric data from the SDSS survey, the spectroscopic data from the SDSS/SEGUE and the LAMOST surveys, and the astrometric data from the Gaia DR2, we have identified 67 highly probable member stars of the GD-1 cold stellar stream spread along almost its entire length (i.e., from 126{deg} to 203{deg} in R.A.). With the accurate spectroscopic (i.e., metallicity and line-of-sight velocity) and astrometric (i.e., proper motions) information, the position-velocity diagrams, i.e., {phi}_1_-{mu}_{alpha}_, {phi}_1_-{mu}_{delta}_, and {phi}_1_-v_gsr_, of the GD-1 stream are well mapped.

The stream has an average metallicity [Fe/H]=-1.96. The rich information of member stars of the stream now available allow one not only to model its origin, but also to place strong constraints on the mass distribution and the gravitational potential of the Milky Way.