TheHubble Space TelescopeKey Project on the Extragalactic Distance Scale. XXVII. A Derivation of the Hubble Constant Using the Fundamental Plane and \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\…

Using published photometry and spectroscopy, we construct the fundamentalplane and D_n-Sigma relations in Leo I, Virgo and Fornax. The published CepheidP-L relations to spirals in these clusters fixes the relation between angularsize and metric distance for both the fundamental plane and D_n-Sigmarelations. Using the locally calibrated fundamental plane, we infer distancesto a sample of clusters with a mean redshift of cz \approx 6000 \kms, andderive a value of H_0=78+- 5+- 9 km/s/Mpc (random, systematic) for the localexpansion rate. This value includes a correction for depth effects in theCepheid distances to the nearby clusters, which decreased the deduced value ofthe expansion rate by 5% +- 5%. If one further adopts the metallicitycorrection to the Cepheid PL relation, as derived by the Key Project, the valueof the Hubble constant would decrease by a further 6%+- 4%. These two sourcesof systematic error, when combined with a +- 6% error due to the uncertainty inthe distance to the Large Magellanic Cloud, a +- 4% error due to uncertaintiesin the WFPC2 calibration, and several small sources of uncertainty in thefundamental plane analysis, combine to yield a total systematic uncertainty of+- 11%. We find that the values obtained using either the CMB, or a flow-fieldmodel, for the reference frame of the distant clusters, agree to within 1%. TheDn-Sigma relation also produces similar results, as expected from thecorrelated nature of the two scaling relations. A complete discussion of thesources of random and systematic error in this determination of the Hubbleconstant is also given, in order to facilitate comparison with the othersecondary indicators being used by the Key Project.Comment: 21 pages, 3 figures, Accepted for publication in Ap