The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVI. The calibration of population II secondary distance indicators and the value of the hubble constant

A Cepheid-based calibration is derived for four distance indicators that ut ilize stars in old stellar populations: the tip of the red giant branch (TR GB), the planetary nebula luminosity function (PNLF), the globular cluster luminosity function (GCLF), and the surface brightness fluctuation method ( SBF). The calibration is largely based on the Cepheid distances to 18 spira l galaxies within ct = 1500 km s(-1) obtained as part of the Hubble Space T elescope (HST) Key Project on the Extragalactic Distance Scale, but relies also on Cepheid distances from separate HST and ground-based efforts. The n ewly derived calibration of the SBF method is applied to obtain distances t o four Abell clusters in the velocity range 3800-5000 km s(-1). Combined wi th cluster velocities corrected for a cosmological flow model, these distan ces imply a value of the Hubble constant of H-0 = 69 +/- 4 (random) +/- 6 ( systematic) km s(-1) Mpc(-1). This result assumes that the Cepheid PL relat ion is independent of the metallicity of the variable stars; adopting a met allicity correction as in Kennicutt et al. would produce a 5% +/- 3% decrea se in H-0. Finally, the newly derived calibration allows us to investigate systematics in the Cepheid, PNLF, SBF, GCLF, and TRGB distance scales.