Colloquium: Prof. Wendy Freedman, University of Chicago
Physics Colloquium Lecture
February 5, 2020
3:00 PM - 4:00 PM
Tension in the Hubble Constant
There has arisen a tension in the value of the Hubble constant measured locally (based on Cepheids and Type Ia supernovae) with that inferred from measurements of the cosmic background radiation, assuming the standard cosmological model. 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 using tip of the red giant branch (TRGB), based on observations with the Hubble Space Telescope Advanced Camera for Surveys. 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, andthe discuss the current tension in Ho.
Date posted
Jan 2, 2020
Date updated
Jan 15, 2020