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SUMMARY:Toward A New Calibration of the Hubble Constant - Wendy Freedman (
 Chicago)
DTSTART:20180531T150000Z
DTEND:20180531T160000Z
UID:TALK104497@talks.cam.ac.uk
CONTACT:28811
DESCRIPTION:I will present new results from the Carnegie-Chicago Hubble Pr
 ogram (CCHP)\,\na decade-long project to independently measure a value of 
 the Hubble\nconstant to very high precision and accuracy. This program l
 everages and\ncombines the resolution of the Hubble Space Telescope\, the 
 long-wavelength\nreach of Spitzer\, the light-gathering capabilities of gr
 ound-based\ntelescopes having a range of aperture sizes and operating wi
 th\nmulti-wavelength detectors\, including dedicated robotic follow-up\nte
 lescopes\, to provide new and independent data for the measurement of\next
 ragalactic distances. The CCHP was initiated in anticipation of the\nlau
 nch of ESA’s Gaia satellite. The goal of the program is to identify\,\nr
 educe and provide external cross-checks on systematic errors in the\ndista
 nce scale. A robust determination of the overall systematic\nuncertaintie
 s in Ho can only be achieved using independent methods of equal\nprecisio
 n. This program includes classical Cepheids\, RR Lyrae variables\, red\n
 giant branch stars\, and Type Ia supernovae\, the latter being part of th
 e\nCarnegie Supernova Project (CSP). By building an entirely new data set 
 from\nthe ground up\,  we have calibrated and applied two independent m
 ethods to\nthe derivation of Ho. The two determinations\, using Cepheids a
 nd red giant\nbranch stars\, respectively\, are demonstrably of high prec
 ision and equally\nhigh systematic accuracy.\n
LOCATION:Sackler Lecture Theatre\, IoA (tea at 3:30 pm)
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