Answering the Most Important Problem in Cosmology Today: Is the Tension in the Hubble Constant Real?
Abstract
Measurements of the Hubble constant are on the cusp of heralding in a fundamental discovery in cosmology that goes beyond the standard Lambda CDM model. Yet published differences in the local distance scale may be indicating that systematic errors, which have long been the bane of the extragalactic distance scale, are larger than currently estimated. The importance of this possibility cannot be overstated. Independent paths for measuring Ho are vital to provide necessary cross checks against unrecognized systematic uncertainties. In this first year of JWST, we propose to measure the distances to half of the current sample of SHoES galaxies that calibrate the Type Ia supernova distance scale using three independent methods in the same galaxies: this will be the first time such a test has been carried out. Each of these methods (Cepheids, the TRGB and carbon stars) are individually of high precision. With its unequalled light-gathering power in space, its infrared sensitivity and high angular resolution, JWST is uniquely poised to provide the most accurate local measurement of the Hubble constant yet to date; and most importantly, it will provide a robust estimate of its systematic uncertainties (currently reddening, metallicity and crowding/blending). As part of its legacy, HST resolved the factor-of-two debate in the Hubble constant, but even with two additional decades of progress, outstanding uncertainties still remain. A legacy of JWST will be the resolution of the current tension, and a robust answer to this question: "Is there new physics required beyond the standard model?"
- Publication:
-
JWST Proposal. Cycle 1
- Pub Date:
- March 2021
- Bibcode:
- 2021jwst.prop.1995F