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SUMMARY:Tension in the Hubble Constant - Wendy Freedman\, University of Ch
 icago
DTSTART:20200527T143000Z
DTEND:20200527T153000Z
UID:TALK141874@talks.cam.ac.uk
CONTACT:Francesca Chadha-Day
DESCRIPTION:Over the last couple of decades\, the accuracy with which we c
 an measure distances to galaxies and determine Ho has improved significant
 ly. I will discuss two of our most precise methods for measuring distances
  in the local universe: Cepheids and the Tip of the Red Giant Branch (TRGB
 ). I will present new results from the Carnegie-Chicago Hubble Program (CC
 HP)\, 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 ne
 w extragalactic distance scale from the ground up.  Using the Hubble Space
  Telescope Advanced Camera for Surveys\, the  CCHP is using the TRGB to ca
 librate Type Ia supernovae. Our value of the Hubble constant\,  Ho = 69.6 
 +/- 0.8 (statistical) +/- 1.7 (systematic) km/sec/Mpc\, falls midway betwe
 en the value obtained from the Planck Cosmic Microwave Background analysis
 \, and that obtained using Cepheids.  I will  address the uncertainties\, 
  discuss the current tension in Ho\, and whether there is need for additio
 nal physics beyond the standard CDM model. 
LOCATION:ONLINE - Details to be sent by email
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