TheHubble Space TelescopeKey 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 tothe spiral galaxy NGC 1326-A, a member of the Fornax cluster of galaxies. Wehave employed data obtained with the Wide Field and Planetary Camera 2 on boardthe Hubble Space Telescope. Over a 49 day interval, a total of twelve V-band(F555W) and eight I-band (F814W) epochs of observation were obtained. Twophotometric reduction packages, ALLFRAME and DoPHOT, have been employed toobtain photometry measures from the three Wide Field CCDs. Variability analysisyields a total of 17 Cepheids in common with both photometry datasets, withperiods ranging between 10 and 50 days. Of these 14 Cepheids with high-qualitylightcurves are used to fit the V and I period-luminosity relations and deriveapparent distance moduli, assuming a Large Magellanic Cloud distance modulus(m-M) (LMC) = 18.50 +- 0.10 mag and color excess E(B-V) = 0.10 mag. AssumingA(V)/E(V-I) = 2.45, the DoPHOT data yield a true distance modulus to NGC 1326-Aof (m-M)_0 = 31.36 +- 0.17 (random) +- 0.13 (systematic) mag, corresponding toa distance of 18.7 \pm 1.5 (random) \pm 1.2 (systematic) Mpc. The deriveddistance to NGC 1326-A is in good agreement with the distance derivedpreviously to NGC 1365, another spiral galaxy member of the Fornax cluster.However the distances to both galaxies are significantly lower than to NGC1425, a third Cepheid calibrator in the outer parts of the cluster.