We report the discovery of distant RR Lyrae stars , including the most distant known in the Milky Way , using data taken in the g - band with the Dark Energy Camera as part of the High cadence Transient Survey ( HiTS ; 2014 campaign ) .
We detect a total of 173 RR Lyrae stars over a \sim 120 deg ^ { 2 } area , including both known RR Lyrae and new detections .
The heliocentric distances d _ { H } of the full sample range from 9 to > 200 kpc , with 18 of them beyond 90 kpc .
We identify three sub-groups of RR Lyrae as members of known systems : the Sextans dwarf spheroidal galaxy , for which we report 46 new discoveries , and the ultra-faint dwarf galaxies Leo IV and Leo V. Following an MCMC methodology , we fit spherical and ellipsoidal profiles of the form \rho ( R ) \sim R ^ { n } to the radial density distribution of RR Lyrae in the Galactic halo .
The best fit corresponds to the spherical case , for which we obtain a simple power-law index of n = -4.17 ^ { +0.18 } _ { -0.20 } , consistent with recent studies made with samples covering shorter distances .
The pulsational properties of the outermost RR Lyrae in the sample ( d _ { H } > 90 kpc ) differ from the ones in the halo population at closer distances .
The distribution of the stars in a Period-Amplitude diagram suggest they belong to Oosterhoff-intermediate or Oosterhoff II groups , similar to what is found in the ultra-faint dwarf satellites around the Milky Way .
The new distant stars discovered represent an important addition to the few existing tracers of the Milky Way potential in the outer halo .