Planetary Nebulae as Standard Candles. IX. The Distance to the Fornax Cluster

We present the results of a planetary nebula (PN) survey of three galaxies in the Fornax Cluster performed with the Cerro Tololo 4 m telescope and on-band off-band [O III] 5007 interference filters. In all, we detected 224 PN candidates: 105 in the peculiar S0/Sa galaxy NGC 1316 (Fornax A), 47 in the E2 galaxy NGC 1404, and 72 in the central cD of the cluster NGC 1399. Using statistically complete samples of planetaries and the procedures described in previous papers in the series, we derive distances to these galaxies from the planetary nebula luminosity function (PNLF). Our distance moduli of 31.13, 31.17, and 31.15 to NGC 1316, 1399, and 1404 show that the cluster is tightly clumped, as suggested by Tonry (1991). By summing the observed PNLFs of the three galaxies, we calculate a mean cluster distance modulus of 31.14±0.14 (16.9±1.1 Mpc) and estimate a Hubble constant of 75±8 km s^-1 Mpc^-1, in excellent agreement with that determined from PN observations in Virgo. We also compare our PNLF distances to those determined from the D_n-σ method and show that the internal uncertainties estimated by both groups are essentially correct.