Revealing Substructure in the Galactic Halo - The SEKBO RR Lyrae Survey

TL;DR

This study uses archival data to identify RR Lyrae stars in the galactic halo, revealing structures associated with the Sagittarius dwarf galaxy and Virgo Over Density, and providing insights into the galaxy's substructure.

Contribution

It presents a new survey of RR Lyrae stars covering 1675 square degrees, mapping halo over-densities and linking them to known galactic structures.

Findings

Identified 2016 RR Lyrae candidates in the halo.

Detected over-densities associated with Sagittarius dwarf galaxy.

Found a new over-density near Virgo Over Density.

Abstract

We present a search for RR Lyrae variable stars from archival observations of the Southern Edgeworth-Kuiper Belt Object survey. The survey covers 1675 square degrees along the ecliptic to a mean depth of V=19.5, i.e. a heliocentric distance of ~50kpc for RR Lyrae stars. The survey reveals 2016 RR Lyrae candidates. Follow-up photometric monitoring of a subset of these candidates shows (24+/-12)% contamination by non-RR Lyrae variables. We derive a map of over-density of RR Lyraes 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 over-density is found on the trailing arm, 200 deg. from the main body of the Sagittarius dwarf at a distance of ~45kpc. 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 over-density is seen towards the Virgo Over Density.