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Allan Sandage and the cosmic expansion

Abstract

This is an account of Allan Sandage's work on(1) The character of the expansion field. For many years he has been the strongest defender of an expanding Universe. He later explained the CMB dipole by a local velocity of 220±50km s−1 toward the Virgo cluster and by a bulk motion of the Local supercluster (extending out to ∼3500km s−1) of 450-500km s−1 toward an apex at l=275, b=12. Allowing for these streaming velocities he found linear expansion to hold down to local scales (∼300km s−1). (2) The calibration of the Hubble constant. Probing different methods he finally adopted—from Cepheid-calibrated SNe Ia and from independent RRLyr-calibrated TRGBs—H 0=62.3±1.3±5.0km s−1 Mpc−

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