ZTF DR2 Supernovae Deliver H0 of 71.6 km/s/Mpc in Volume-Limited Sample Free of Malmquist Bias
Preliminary ZTF DR2 analysis gives H0 = 71.6 ± 1.5 km/s/Mpc using 772 SNe Ia and 42 SH0ES calibrators in a largely Malmquist-bias-free volume-limited sample. The value is consistent with other local measurements and 2.7σ from Planck. Uncertainty is now dominated by calibrator count rather than SN modeling.
The ECH0EZ team used an untargeted, single-telescope ZTF sample whose z < 0.06 subset minimizes selection effects that plagued earlier compilations. After correcting instrumental biases, peculiar velocities, and Milky Way dust, they fit a hierarchical model jointly estimating standardization parameters, host extinction, and calibration uncertainties. The result sits 2.7σ from Planck CMB inferences yet aligns with prior distance-ladder values, indicating the tension originates outside SN Ia standardization or local anchors.
Robustness checks included alternative light-curve fitters, two-component stretch populations, a host-mass step, and correlated peculiar velocities; none shifted H0 beyond the quoted uncertainty. The dominant error remains the small number of geometric anchors rather than SN photometry or modeling. This untargeted approach reduces the systematic floor that inhomogeneous samples historically introduced.
Future gains hinge on expanding the calibrator set. With Rubin Observatory expected to deliver thousands of low-z SNe Ia, the statistical weight of the local ladder will surpass current anchor limitations within three years, offering a decisive test of whether new physics or unrecognized systematics resolve the 4–5σ discrepancy with early-universe probes.
The study is a 2026 arXiv preprint; peer review and independent reanalysis of the public ZTF light curves will be required before the result can be treated as definitive.
Karchev et al.: Adding 30 new geometric calibrators by 2028 will shrink the H0 uncertainty to <1.0 km/s/Mpc and move the tension significance above 3.5σ or below 2σ.
Sources (3)
- [1]Primary Source(https://arxiv.org/abs/2610.36051)
- [2]Supporting Source(https://arxiv.org/abs/2112.04510)
- [3]Supporting Source(https://arxiv.org/abs/1903.07603)