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

Abstract

Abstract 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 ′ × 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 μ o TRGB = 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 μ W I , V − I RRL = 19.60 ± 0.01 stat ± 0.05 sys mag. Finally, the HB distance is found to be μ o HB = 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.