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Colloquium | Physics Division

The Current Tension in the Hubble Constant

PHY Colloquium

Abstract: I will present new results from the Carnegie-Chicago Hubble Program (CCHP), the goal of which is to independently measure a value of the Hubble constant to very high precision and accuracy. We have built an entirely new extragalactic distance scale from the ground up. Using the Hubble Space Telescope Advanced Camera for Surveys, the CCHP is using the tip of the red giant branch (TRGB) to calibrate Type Ia supernovae. Our supernova sample comes from the Carnegie Supernova Project, carried out at Las Campanas, Chile. Our value of the Hubble constant, Ho = 69.8, with statistical and systematic uncertainties of 0.8 and 1.7 km/sec/Mpc, respectively, falls midway between the value obtained from the Planck Cosmic Microwave Background analysis, and that obtained using Cepheids. I will address the uncertainties, and the discuss the current tension in Ho.

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