High H 0 Values from CMB E-mode Data: A Clue for Resolving the Hubble Tension?

Abstract

The E-mode (EE) CMB power spectra measured by Planck, ACTPol, and SPTpol constrain the Hubble constant to be 70.0 ± 2.7, , and km s −1 Mpc −1 within the standard ΛCDM model (posterior mean and central 68% interval bounds). These values are higher than the constraints from the Planck temperature (TT) power spectrum, and consistent with the Cepheid-supernova distance ladder measurement H 0 = 73.2 ± 1.3 km s −1 Mpc −1 . If this preference for a higher value was strengthened in a joint analysis it could provide an intriguing hint at the resolution of the Hubble disagreement. We show, however, that combining the Planck, ACTPol, and SPTpol EE likelihoods yields H 0 = 68.7 ± 1.3 km s −1 Mpc −1 , 2.4 σ lower than the distance ladder measurement. This is due to different degeneracy directions across the full parameter space, particularly involving the baryon density, Ω b h 2 , and scalar tilt, n s , arising from sensitivity to different multipole ranges. We show that the E-mode ΛCDM constraints are consistent across the different experiments within 1.4 σ , and with the Planck TT results at 0.8 σ . Combining the Planck, ACTPol, and SPTpol EE data constrains the phenomenological lensing amplitude, A L = 0.89 ± 0.10, consistent with the expected value of unity.