Optical Surface Brightness Fluctuations of Shell Galaxies toward 100 Mpc

Abstract

We measure F814W surface brightness fluctuations (SBFs) for a sample of distant shell galaxies with radial velocities ranging from 4000 to 8000 km s<SUP>-1</SUP>. The distance at galaxies is then evaluated by using the SBF method. For this purpose, theoretical SBF magnitudes for the HST ACS filters are computed for single-burst stellar populations covering a wide range of ages (t = 1.5-14 Gyr) and metallicities (Z = 0.008-0.04). Using these stellar population models, we provide the first bar M<SUB>F814W</SUB> versus (F 475W - F 814W)<SUB>0</SUB> calibration and we extend the previous M<SUB>1</SUB> versus (B - I)<SUB>0</SUB> color relation to colors (B - I)<SUB>0</SUB> <= 2.0 mag. Coupling our SBF measurements with the theoretical calibration we derive distances with a statistical uncertainty of ~8%, and systematic error of ~6%. The procedure developed to analyze data ensures that the indetermination due to possible unmasked residual shells is well below ~12%. The results suggest that optical SBFs can be measured at d >= 100 Mpc with HST ACS imaging. SBF-based distances coupled with recession velocities corrected for peculiar motion, allow us obtain H<SUB>0</SUB> = 76 +/- 6 (statistical) ±5 (systematic) km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>.