Galactic tides and the Crater II dwarf spheroidal: a challenge to LCDM?

Understand

The unusually low velocity dispersion and large size of Crater II pose a challenge to our understanding of dwarf galaxies in the Lambda Cold Dark Matter (LCDM) cosmogony.

• The low velocity dispersion suggests either a dark halo mass much lower than the minimum expected from hydrogen cooling limit arguments, or one that is in the late stages of extreme tidal stripping.
• The tidal interpretation has been favoured in recent work and is supported by the small pericentric distances consistent with available kinematic estimates.
• We use N-body simulations to examine this interpretation in detail, assuming a Navarro-Frenk-White (NFW) profile for Crater II's progenitor halo.