RR Lyrae stars as tracers of halo substructures.

Three RR Lyrae overdensity candidates in the southern sky have been studied using low resolution spectra obtained with the Goodman spectrograph at SOAR. We search for unidentified velocity peaks indicative of the possible presence of streams within the overdensities. Our results suggest that all three overdensities present an excess of radial velocity signal at high mean radial velocities which cannot be explained as a contribution from any known Galactic component. [ABSTRACT FROM AUTHOR]