CosmoVerse seminar: Wendy Freedman

What We are Learning from JWST About the Hubble Tension

I will describe results from a new JWST program to improve measurements of the Hubble constant. The 10 times greater sensitivity and 4 times higher resolution of JWST in the near-infrared provide a powerful means of addressing challenges in previous measurements of the extragalactic distance scale. Distances to a sample of Type Ia supernova hosts have been measured using three independent astrophysical routes: 1) the Tip of the Red Giant Branch (TRGB) 2) the luminosity function of JAGB/carbon stars and 3) the Cepheid period-luminosity relation. These three measurements provide a constraint on the systematic uncertainties in the distances that set the local calibration for the Hubble constant. All of the distances are anchored to the geometric distance for the maser galaxy, NGC 4258, also observed with JWST. The TRGB and JAGB distances agree at the 1% level, and the agreement with Cepheids is 2.5-4%. Tying into the sample of Type Ia supernovae (SNeIa) from the Carnegie Supernova Project and combining the results for the three distance indicators leads to value of the Hubble constant of 69.96 +/- 1.05 (stat) +/- 1.12 km/sec/Mpc. These results are consistent with both the standard model Lambda CDM model and with the existence of a Hubble tension. The TRGB and JAGB measurements rely on JWST measurements alone and lead to a smaller value of Ho = 69.03 ± 1.75 (total uncertainty). Larger samples of JWST measurements will be required to address both the statistical and the systematic uncertainties in the current sample of SNeIa host galaxies.

Like our socials: