The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXII. The Discovery of Cepheids in NGC 1326A

We report on the detection of Cepheids and the first distance measurement to the spiral galaxy NGC 1326A, a member of the Fornax Cluster of galaxies. We have employed data obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Over a 49 day interval, a total of 12 V-band (F555W) and eight I-band (F814W) epochs of observation were obtained. Two photometric reduction packages, ALLFRAME and DoPHOT, have been employed to obtain photometry measures from the three Wide Field CCDs. Variability analysis yields a total of 17 Cepheids in common with both photometry data sets, with periods ranging between 10 and 50 days. Of these, 14 Cepheids with high-quality light curves are used to fit the V and I period-luminosity relations and derive apparent distance moduli, assuming a Large Magellanic Cloud distance modulus μLMC = 18.50 ± 0.10 mag and color excess E(B-V) = 0.10 mag. Assuming A(V)/E(V-I) = 2.45, the DoPHOT data yield a true distance modulus to NGC 1326A of μ0 = 31.36 ± 0.17(random) ± 0.13(systematic) mag, corresponding to a distance of 18.7 ± 1.5(random) ± 1.2(systematic) Mpc. The derived distance to NGC 1326A is in good agreement with the distance derived previously to NGC 1365, another spiral galaxy member of the Fornax Cluster. However, the distances to both galaxies are significantly lower than that to NGC 1425, a third Cepheid calibrator in the outer parts of the cluster.