Distances to Local Group Galaxies via Population II, Stellar Distance Indicators. I. The Sculptor Dwarf Spheroidal

We determine the distance to the Sculptor Dwarf Spheroidal via three Population II stellar distance indicators: (a) the Tip of the Red Giant Branch (TRGB), (b) RR Lyrae variables (RRLs), and (c) the ridgeline of the blue horizontal branch (HB). High signal-to-noise, wide-field VI imaging that covers an area 48' x 48' and reaches a photometric depth approximately 2 mag fainter than the HB was acquired with the Magellan-Baade 6.5 m telescope. The true modulus derived from Sculptor's TRGB is found to be mu(TRGB)(0) = 19.59 +/- 0.07(stat) +/- 0.05(sys) mag. Along with periods adopted from the literature, newly acquired RRL phase points are fit with template light curves to determine mu(RRL)(1,V-1) 19.60 +/- 0.01(stat) +/- 0.05(sys) mag. Finally, the HB distance is found to be it mu(HB)(0) = 19.54 +/- 0.03(stat) +/- 0.09(sys) mag. Absolute calibrations of each method are anchored by independent geometric zero-points, utilize a different class of stars, and are determined from the same photometric calibration.