Cosmological constraints from the tomography of DES-Y3 galaxies with CMB lensing from ACT DR4

TL;DR

This study measures the cross-correlation between DES Y3 galaxies and ACT DR4 CMB lensing to constrain cosmological parameters, finding a lower S8 value than Planck with mild statistical significance.

Contribution

It provides a novel joint analysis of galaxy-CMB lensing cross-correlations over multiple redshift bins, improving constraints on cosmological parameters.

Findings

Detected a 9.1σ correlation between galaxies and CMB lensing

Measured S8 = 0.75^{+0.04}_{-0.05}

Results favor a lower S8 than Planck, with <2σ significance

Abstract

We present a measurement of the cross-correlation between the MagLim galaxies selected from the Dark Energy Survey (DES) first three years of observations (Y3) and cosmic microwave background (CMB) lensing from the Atacama Cosmology Telescope (ACT) Data Release 4 (DR4), reconstructed over $\sim 436$ sq.deg. of the sky. Our galaxy sample, which covers $\sim 4143$ sq.deg., is divided into six redshift bins spanning the redshift range of $0.20<z<1.05$. We adopt a blinding procedure until passing all consistency and systematics tests. After imposing scale cuts for the cross-power spectrum measurement, we reject the null hypothesis of no correlation at 9.1\sigma. We constrain cosmological parameters from a joint analysis of galaxy and CMB lensing-galaxy power spectra considering a flat \LCDM model, marginalized over 23 astrophysical and systematic nuisance parameters. We find the clustering amplitude $S_8\equiv \sigma_8 (\Omega_m/0.3)^{0.5} = 0.75^{+0.04}_{-0.05}$. In addition, we constrain the linear growth of cosmic structure as a function of redshift. Our results are consistent with recent DES Y3 analyses and suggest a preference for a lower $S_8$ compared to results from measurements of CMB anisotropies by the Planck satellite, although at a mild level ($< 2 \sigma$) of statistical significance.