Kavli Affiliate: Wendy L. Freedman
| First 5 Authors: Quang H. Tran, Taylor J. Hoyt, Wendy L. Freedman, Barry F. Madore, Elias K. Oakes
| Summary:
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 $48′ times 48’$ and reaches a photometric depth approximately 2
mag fainter than the HB was acquired with the Magellan-Baade 6.5m telescope.
The true modulus derived from Sculptor’s TRGB is found to be
$mu^mathrm{TRGB}_o = 19.59 pm 0.07_mathrm{stat} pm 0.05_mathrm{sys}$ mag.
Along with periods adopted from the literature, newly acquired RRL phase points
are fit with template light curves to determine $mu_{W_{I,V-I}}^mathrm{RRL} =
19.60 pm 0.01_mathrm{stat} pm 0.05_mathrm{sys}$ mag. Finally, the HB
distance is found to be $mu^mathrm{HB}_o = 19.54 pm 0.03_mathrm{stat} pm
0.09_mathrm{sys}$ mag. Absolute calibrations of each method are anchored by
independent geometric zero-points, utilizes a different class of stars, and are
determined from the same photometric calibration.
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