| DISTANCE TO THE FORNAX CLUSTER USING THE HUBBLE SPACE TELESCOPE: IMPLICATIONS FOR COSMOLOGY (2007) | |||||||||||||
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| ABSTRACT Using the Hubble Space Telescope (HST), we have discovered Cepheid variables in the Fornax cluster spiral galaxy, NGC 1365. V and I period-luminosity relations for 37 Cepheids with periods between 12 and 60 days give a true tnodulus of p,, = 31.43+0.06 nmg, corresponding to a distance of 19.3+ 0.6 Mpc. Associating this distance with the Fornax cluster as a whole, and adopting a mean recessional velocity of 1,318~39 knl/sec (corrected to the barycentre of the Local Group and for Virgocentric flow) gives a local Hubble constant of 110 = 68 + 7 km/sec/Mpc. The quoted random error is 10~0, uncertainty is the currently ( unknown) largescale-flow velocity of the cluster. while the largest systematic correction to the cosmological Seven Cepheid-based distances to groups of galaxies out to and including the Virgo and Fornax clusters yield [10 = 70+3 km/sec/Mpc. Recalibrating the Tully-Fisher | |||||||||||||
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