AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 39. Results from the HST Key Project on the Extragalactic Distance Scale
Topical, Oral, Tuesday, June 1, 1999, 8:30-10:00am, 10:45am-12:30pm, 2:30-4:00pm, International Ballroom South

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[39.06] The Calibration of Population II Secondary Distance Indicators and the Value of the Hubble Constant

L. Ferrarese (Caltech), J.R. Mould (MSSSO), R.C. Kennicutt (Steward Observatory), J. Huchra (CfA), H.C. Ford (JHU), P.B. Stetson (DAO), B.F. Madore (IPAC), W.L. Freedman (OCIW), S. Sakai (NOAO), B.K. Gibson (UofC), J.A. Graham (DTM, CIW), S.M. Hughes (RGO), G.D. Illingworth (UCSC), D.D. Kelson (DTM, CIW), L. Macri (CfA), A. Saha (NOAO), K. Sebo (MSSSO), N.A. Silbermann (IPAC)

A Cepheid based calibration is presented for four distance indicators that utilize stars in the old stellar populations: the tip of the red giant branch, the planetary nebulae luminosity function, the globular cluster luminosity function and the surface brightness fluctuation method. The calibration is largely based on the Cepheid distances to 18 spiral galaxies within 1500 km s-1 obtained as part of the HST Key Project on the Extragalactic Distance Scale, but relies also on Cepheid distances from separate HST and ground based efforts. An inter-comparison of the Cepheid, PNLF, SBF, GCLF and TRGB distance scales allows us to test each of the distance indicators for biases, and constrain the metallicity dependence of the Cepheid PL relation. The newly derived calibration of the SBF method is applied to determine distances to four Abell clusters in the redshift range between 3800 and 5000 km s-1, observed using the HST/WFPC2. Combined with cluster velocities corrected for a cosmological flow model, these distances allow the determination of the Hubble constant within 15%.

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