Impact of ACT DR6 and DESI DR2 for Early Dark Energy and the Hubble tension

TL;DR

This paper updates constraints on Early Dark Energy using ACT DR6 and DESI DR2 data, showing EDE can still help resolve the Hubble tension but with residual discrepancies, and highlights the importance of prior-volume effects in Bayesian analyses.

Contribution

It provides new constraints on EDE parameters with recent ACT and DESI data, demonstrating EDE's viability in addressing the Hubble tension and analyzing prior-volume effects.

Findings

ACT DR6 allows larger EDE contribution than Planck NPIPE.

Including DESI DR2 reduces tension with SH0ES to ~2 sigma.

EDE with H0=73 km/s/Mpc fits data better than ΛCDM.

Abstract

The data release six of the Atacama Cosmology Telescope (ACT DR6) and the second data release from the Dark Energy Spectroscopic Instrument (DESI DR2) recently became available. In light of these data, we update constraints on the Early Dark Energy (EDE) resolution to the Hubble tension. While ACT DR6 does not favor EDE over the core cosmological model $\Lambda$CDM, it allows for a significantly larger maximum contribution of EDE, $f_{\rm EDE}$, in the pre-recombination era than the latest analysis of {\it Planck} NPIPE despite increased precision at small angular scales. Moreover, EDE rises the value of $H_0r_s$, improving consistency between CMB and DESI DR2 data. We find a residual tension with SH0ES of $\sim 2 \sigma$ for the combination of {\it Planck} at $\ell <1000$ + ACT DR6 + lensing + Pantheon-plus + DESI DR2, a significant decrease from $3.7 \sigma$ for analyses that use NPIPE and SDSS BAO data. A profile likelihood analysis reveals significant prior-volume effects in Bayesian analyses which do not include SH$0$ES, with confidence intervals of $f_{\rm EDE}=0.09\pm 0.03$ and $H_0= 71.0\pm1.1$ km/s/Mpc. When including DESI data, the EDE model with $H_0=73$ km/s/Mpc provides a better fit than the $\Lambda$CDM model with $H_0=68.4$ km/s/Mpc. The inclusion of SH$0$ES data rises the preference well above $5\sigma$, with $\Delta\chi^2=-35.4$. Our work demonstrates that after ACT DR6 and DESI DR2, EDE remains a potential resolution to the Hubble tension.