Speaker
Description
We recalibrate the anchor sample of the L–σ relation for HII Galaxies (HIIG), an independent three-rung distance estimator that uses Giant Extragalactic HII Regions (GEHR) as local anchors. GEHR and HIIG are blue massive starburst systems that exhibit a seemingly ubiquitous correlation between their H-beta (Balmer) luminosity and their spectroscopic velocity dispersion, known as the L-σ relation. Although the L–σ method is very promising, particularly given the redshift range it expands to (z ~ 7), its systematic error budget remains much less explored than that of the SN Ia method. Using a hierarchical Bayesian framework on 32 homogenized host-galaxy distance moduli (Cepheid and TRGB, 26 yr of NED literature), we find H0 = 74.1 +/- 3.8 km/s/Mpc with Cepheid anchors (consistent with SH0ES) and H0 = 67.3 +/- 3.8 km/s/Mpc with TRGB anchors (consistent with Planck and CCHP). The joint fit yields h = 0.721 +/- 0.039. This anchor-dependent split could suggest part of the Hubble tension may trace back to systematics within the distance ladder itself, rather than to new physics alone.