High $H_0$ Values from CMB E-mode Data: A Clue for Resolving the Hubble Tension?

TL;DR

This study analyzes E-mode CMB data from multiple experiments to investigate the Hubble constant, revealing tensions and consistencies within the standard cosmological model and implications for the Hubble tension problem.

Contribution

It provides a combined analysis of EE CMB data from Planck, ACTPol, and SPTpol, highlighting the impact of degeneracy directions on H0 estimates and consistency across experiments.

Findings

EE data suggest higher H0 values compatible with local measurements.

Combined EE data yield H0 lower than local measurements, indicating tension.

Constraints on lensing amplitude are consistent with expectations.

Abstract

The E-mode (EE) CMB power spectra measured by Planck, ACTPol, and SPTpol constrain the Hubble constant to be $70.0\pm2.7$, $72.4^{+3.9}_{-4.8}$, and $73.1^{+3.3}_{-3.9}$ km s$^{-1}$ Mpc$^{-1}$ within the standard $\Lambda$CDM 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 $H_0=73.2\pm1.3$ 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 $H_0=68.7\pm1.3$ km s$^{-1}$ Mpc$^{-1}$, $2.4\sigma$ lower than the distance ladder measurement. This is due to different degeneracy directions across the full parameter space, particularly involving the baryon density, $\Omega_bh^2$, and scalar tilt, $n_s$, arising from sensitivity to different multipole ranges. We show that the E-mode $\Lambda$CDM constraints are consistent across the different experiments within $1.4\sigma$, and with the Planck TT results at $0.8\sigma$. Combining the Planck, ACTPol, and SPTpol EE data constrains the phenomenological lensing amplitude, $A_L=0.89\pm0.10$, consistent with the expected value of unity.