Velocity Dispersion of the GD-1 Stellar Stream

Abstract Tidally dissolved globular clusters form thin stellar streams that preserve a historical record of their past evolution. We report radial velocity dispersion 2.1 ± 0.3 km s −1 in the GD-1 stream using sample 43 spectroscopically confirmed members. The is constant over surveyed ≈15° span stream. also measured spur adjacent to main stream, and found similar value at tip spur. Surprisingly, region closer appears dynamically colder than An unperturbed model has ≈0.5 , indicating undergone dynamical heating. Stellar arising from clusters, which prior arrival Milky Way, orbited dwarf galaxy with cored density profile are expected have experienced amount heating required match observed GD-1. This suggests been accreted imprints its original host galaxy, including inner slope dark matter halo, remain observable today.