Revealing substructure in the galactic halo: The SEKBO RR Lyrae survey

We present a search for RR Lyrae variable stars from archival observations of the Southern Edgeworth-Kuiper Belt Object survey. The survey covers 1675 deg(2) along the ecliptic to a mean depth of V = 19.5, i.e., a heliocentric distance of similar to 50 kpc for RR Lyrae stars. The survey reveals 2016 RR Lyrae candidates. Follow-up photometric monitoring of a subset of these candidates shows similar to 24% contamination by non-RR Lyrae variables. We derive a map of overdensity of RR Lyrae stars in the halo that reveals a series of structures coincident with the leading and trailing arms of debris from the Sagittarius dwarf galaxy. One of the regions of overdensity is found on the trailing arm, 200 degrees from the main body of the Sagittarius dwarf at a distance of similar to 45 kpc. This distant detection of the stellar population of the outer trailing arm of Sagittarius offers a tight constraint on the motion of the dwarf galaxy. A distinctly separate region of overdensity is seen toward the Virgo overdensity.