The origin of failed subhaloes and the common mass scale of the Milky Way satellite galaxies

Understand

We study the formation histories and present-day structure of satellite galaxies formed in a high resolution hydrodynamic simulation of a Milky Way-like galaxy.

• The simulated satellites span nearly 4 orders of magnitude in luminosity but have a very similar mass within their inner 600 pc, ~ 3 10^7 M_solar, with very little scatter.
• This result is in agreement with the recent measurements for dwarf spheroidal galaxies (dSphs) in the Milky Way by Strigari et al.
• In our simulations a preferred mass scale arises naturally from the effects of the early reionisation of gas.