The Hubble Space Telescope key project on the extragalactic distance scale. XIV. The Cepheids in NGC 1365 Academic Article uri icon


  • We report the detection of Cepheid variable stars in the barred spiral galaxy NGC 1365, located in the Fornax cluster, using the Hubble Space Telescope (HST) Wide Field and Planetary Camera 2 (WFPC2). Twelve V (F555W) and four I (F814W) epochs of observation were obtained. The two photometry packages ALLFRAME and DoPHOT were separately used to obtain profile-fitting photometry of all the stars in the HST field. The search for Cepheid variable stars resulted in a sample of 52 variables, with periods between 14 and 60 days, common to both data sets. ALLFRAME photometry and light curves of the Cepheids are presented. A subset of 34 Cepheids were selected on the basis of period, light curve shape, similar ALLFRAME and DoPHOT periods, color, and relative crowding, to fit the Cepheid period-luminosity relations in V and I for both ALLFRAME and DoPHOT. The measured distance modulus to NGC 1365 from the ALLFRAME photometry is 31.31 0.20 (random) 0.18 (systematic) mag, corresponding to a distance of 18.3 1.7 (random) + 1.6 (systematic) Mpc. The reddening is measured to be E(V - I) = 0.16 0.08 mag. These values are in excellent agreement with those obtained using the DoPHOT photometry, namely a distance modulus of 31.26 0.10 mag and a reddening of 0.15 0.10 mag (internal errors only).

published proceedings

  • Astrophysical Journal

author list (cited authors)

  • Silbermann, N. A., Harding, P., Ferrarese, L., Stetson, P. B., Madore, B. F., Kennicutt, R. C., ... Turner, A.

complete list of authors

  • Silbermann, NA||Harding, P||Ferrarese, L||Stetson, PB||Madore, BF||Kennicutt, RC||Freedman, WL||Mould, JR||Bresolin, F||Ford, H||Gibson, BK||Graham, JA||Han, M||Hoessel, JG||Hill, RJ||Huchra, J||Hughes, SMG||Illingworth, GD||Kelson, D||Macri, L||Phelps, R||Rawson, D||Sakai, S||Turner, A

publication date

  • April 1999