Weak Galactic halo--dwarf spheroidal connection from RR Lyrae stars

Understand

We discuss the role that dwarf galaxies may have played in the formation of the Galactic halo (Halo) using RR Lyrae stars (RRL) as tracers of their ancient stellar component.

• The comparison is performed using two observables (periods, luminosity amplitudes) that are reddening and distance independent.
• Fundamental mode RRL in six dwarf spheroidals and eleven ultra faint dwarf galaxies (1,300) show a Gaussian period distribution well peaked around a mean period of <Pab>=0.610+-0.001 days (sigma=0.03).
• The Halo RRL (15,000) are characterized by a broader period distribution.