Kavli Affiliate: Alexander P. Ji
| First 5 Authors: Ting S. Li, Alexander P. Ji, Andrew B. Pace, Denis Erkal, Sergey E. Koposov
| Summary:
We report the kinematic, orbital, and chemical properties of 12 stellar
streams with no evident progenitors, using line-of-sight velocities and
metallicities from the Southern Stellar Stream Spectroscopic Survey ($S^5$),
proper motions from $Gaia$ EDR3, and distances derived from distance tracers or
the literature. This data set provides the largest homogeneously analyzed set
of streams with full 6D kinematics and metallicities. All streams have
heliocentric distances between ${sim}10-50$ kpc. The velocity and metallicity
dispersions show that half of the stream progenitors were disrupted dwarf
galaxies (DGs), while the other half originated from disrupted globular
clusters (GCs), hereafter referred to as DG and GC streams. Based on the mean
metallicities of the streams and the mass-metallicity relation, the
luminosities of the progenitors of the DG streams range between Carina and Ursa
Major I ($-9.5lesssim M_Vlesssim-5.5$). Four of the six GC streams have mean
metallicities of [Fe/H]$< -2$, more metal-poor than typical Milky Way (MW) GCs
at similar distances. Interestingly, the 300S and Jet GC streams are the only
streams on retrograde orbits in our dozen stream sample. Finally, we compare
the orbital properties of the streams with known DGs and GCs in the MW, finding
several possible associations. Some streams appear to have been accreted with
the recently discovered Gaia-Enceladus-Sausage system, and others suggest that
GCs were formed in and accreted together with the progenitors of DG streams
whose stellar masses are similar to Draco to Carina ($sim10^5-10^6M_odot$).
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