Final Results from theHubble Space TelescopeKey Project to Measure the Hubble Constant

We present here the final results of the Hubble Space Telescope Key Projectto measure the Hubble constant. We summarize our method, the results and theuncertainties, tabulate our revised distances, and give the implications ofthese results for cosmology. The analysis presented here benefits from a numberof recent improvements and refinements, including (1) a larger LMC Cepheidsample to define the fiducial period-luminosity (PL) relations, (2) a morerecent HST Wide Field and Planetary Camera 2 (WFPC2) photometric calibration,(3) a correction for Cepheid metallicity, and (4) a correction forincompleteness bias in the observed Cepheid PL samples. New, revised distancesare given for the 18 spiral galaxies for which Cepheids have been discovered aspart of the Key Project, as well as for 13 additional galaxies with publishedCepheid data. The new calibration results in a Cepheid distance to NGC 4258 inbetter agreement with the maser distance to this galaxy. Based on these revisedCepheid distances, we find values (in km/sec/Mpc) of H0 = 71 +/- 2 (random) +/-6 (systematic) (type Ia supernovae), 71 +/- 2 +/- 7 (Tully-Fisher relation), 70+/- 5 +/- 6 (surface brightness fluctuations), 72 +/- 9 +/- 7 (type IIsupernovae), and 82 +/- 6 +/- 9 (fundamental plane). We combine these resultsfor the different methods with 3 different weighting schemes, and find goodagreement and consistency with H0 = 72 +/- 8. Finally, we compare these resultswith other, global methods for measuring the Hubble constant.Comment: Accepted to the Astrophysical Journal, 10 figure