2022ApJ...929..116O

We determine three independent Population II distance moduli to the Fornax dwarf spheroidal (dSph) galaxy, using wide-field, ground-based VI imaging acquired with the Magellan-Baade telescope at Las Campanas Observatory. After subtracting foreground stars using Gaia EDR3 proper motions, we measure an I-band tip of the red giant branch (TRGB) magnitude of {I}_{0}^{\mathrm{TRGB}}=16.753\pm {0.03}_{\mathrm{stat}}\pm {0.037}_{\mathrm{sys}} mag, with a calibration based in the LMC giving a distance modulus of {\mu }_{0}^{\mathrm{TRGB}}=20.80\pm {0.037}_{\mathrm{stat}}\pm {0.057}_{\mathrm{sys}} mag. We determine an RR Lyrae (RRL) distance from template mean magnitudes, with periods adopted from the literature. Adopting a Gaia DR2 calibration of first overtone RRL period-luminosity and period-Wesenheit relations, we find {\mu }_{0}^{\mathrm{PLZ}}=20.74\pm {0.01}_{\mathrm{stat}}\pm {0.12}_{\mathrm{sys}} mag and {\mu }_{0}^{\mathrm{PWZ}}=20.68\pm {0.02}_{\mathrm{stat}}\pm {0.07}_{\mathrm{sys}} mag. Finally, we determine a distance from Fornax's horizontal branch (HB) and two galactic globular cluster calibrators, giving {\mu }_{0}^{\mathrm{HB}}=20.83\pm {0.03}_{\mathrm{stat}}\pm {0.09}_{\mathrm{sys}} mag. These distances are each derived from homogeneous IMACS photometry, are anchored to independent geometric zero-points, and utilize different classes of stars. We therefore average over independent uncertainties and report the combined distance modulus <µ₀> =20.770 ± 0.042_stat ± 0.024_sys mag (corresponding to a distance of 143 ± 3 kpc).