The Extragalactic Distance Scale Key Project XVIII. The Discovery of Cepheids and a New Distance to NGC 4535 Using the Hubble Space Telescope

摘要

We report on the discovery of Cepheids in the Virgo spiral galaxy NGC 4535,based on observations made with the Wide Field and Planetary Camera 2 on boardthe Hubble Space Telescope. NGC 4535 is one of 18 galaxies observed as a partof The HST Key Project on the Extragalactic Distance Scale which aims tomeasure the Hubble constant to 10% accuracy. NGC 4535 was observed over 13epochs using the F555W filter, and over 9 epochs using the F814W filter. TheHST F555W and F814W data were transformed to the Johnson V and Kron-Cousins Imagnitude systems, respectively. Photometry was performed using two independentprograms, DoPHOT and DAOPHOT II/ALLFRAME. Period-luminosity relations in the V and I bands were constructed using 39high-quality Cepheids present in our set of 50 variable candidates. We obtain adistance modulus of 31.02+/-0.26 mag, corresponding to a distance of 16.0+/-1.9Mpc. Our distance estimate is based on values of mu = 18.50 +/- 0.10 mag andE(V-I) = 0.13 mag for the distance modulus and reddening of the LMC,respectively.