Using Surface Brightness Fluctuations to Study Nearby Satellite Galaxy Systems: Calibration and Methodology

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We explore the use of ground-based surface brightness fluctuation (SBF) measurements to constrain distances to nearby dwarf galaxies. Using archival CFHT Megacam imaging data for a sample of 28 nearby dwarfs, we demonstrate that reliable SBF measurements and distances accurate to 15% are possible even for very low surface brightness ( μ 0 i > 24 mag arcsec −2 ) galaxies with modest, ∼hour-long exposures with CFHT. Combining our sample with a recent sample of six dwarfs with SBF measured with Hubble Space Telescope ( HST ) from the literature, we provide the most robust empirical SBF calibration to date for the blue colors expected for these low-mass systems. Our calibration is credible over the color range 0.3 ≲ g − i ≲ 0.8 mag. It is also the first SBF calibration tied completely to tip of the red giant branch (TRGB) distances as each galaxy in the sample has a literature TRGB distance. We find that even though the intrinsic scatter in SBF increases for blue galaxies, the rms scatter in the calibration is still ≲0.3 mag. We verify our measurements by comparing with HST SBF measurements and detailed image simulations. We argue that ground-based SBF is a very useful tool for characterizing dwarf satellite systems and field dwarfs in the nearby, D ≲ 20 Mpc universe.