Speaker
Description
The dark matter subhalos in the Milky Way that encounter a globular cluster's stellar stream increases its velocity spread. The continued dissolution of the cluster maintains a thin, low velocity dispersion in the stream. Several streams that orbit in the 15-25 kpc range now have well measured cocoon velocity spreads up to 10 km/sec. Such a velocity spread cannot be created in a smooth galactic halo and the orbital range is insensitive to stream interacations with the bar, dwarf galaxies and the LMC. The current day subhalo population is insufficient to heat the streams. A cosmologically evolving CDM subhalo population, which has much larger numbers at early times, acting for the isochrone age of the stream can create the observed velocities. The current data are mildly incompatible with WDM models, however, future data will provide good constraints.
