The Distances to Open Clusters from Main-sequence Fitting. Iv. Galactic Cepheids, the Lmc, and the Local Distance Scale

We derive the basic properties of seven Galactic open clusters containing Cepheids and construct their periodluminosity (P-L) relations. For our cluster main-sequence fitting we extend previous Hyades-based empirical color-temperature corrections to hotter stars using the Pleiades as a template. We use BVICJHKs data to test the reddening law, and include metallicity effects to perform a more comprehensive study for our clusters than prior efforts. The ratio of total to selective extinction RV that we derive is consistent with expectations. Assuming the LMC P-L slopes, we find 〈MV 〉 = −3.93±0.07 (statistical)±0.14 (systematic) for 10-day period Cepheids, which is generally fainter than those in previous studies. Our results are consistent with recent HST and Hipparcos parallax studies when using the Wesenheit magnitudes W (VI). Uncertainties in reddening and metallicity are the major remaining sources of error in the V -band P-L relation, but a higher precision could be obtained with deeper optical and near-infrared cluster photometry. We derive distances to NGC 4258, the LMC, and M33 of (m − M)0 = 29.28± 0.10, 18.34± 0.06, and 24.55± 0.28, respectively, with an additional systematic error of 0.16 mag in the P-L relations. The distance to NGC 4258 is in good agreement with the geometric distance derived from water masers [∆(m − M)0 = 0.01±0.24]; our value for M33 is less consistent with the distance from an eclipsing binary [∆(m − M)0 = 0.37±0.34]; our LMC distance is moderately shorter than the adopted distance in the HST Key Project, which formally implies an increase in the Hubble constant of 7%±8%. Subject headings: Cepheids — distance scale — galaxies: individual (M33, NGC 4258) — Magellanic Clouds — open clusters and associations: general — stars: distances