First Cosmological Constraints from the Joint Analysis of Galaxy Clustering and the Kinetic Sunyaev-Zel'dovich Effect

TL;DR

This work addresses degeneracies between cosmic expansion and growth of structure by performing the first real-data joint analysis of galaxy clustering (GC) and the kinetic SZ (kSZ) effect, using CMASS galaxies and ACT DR6 maps. It combines GC multipoles with the kSZ dipole, achieving a signal-to-noise of about $7$ for the kSZ and providing tight constraints on the growth rate and expansion geometry, e.g., $f=0.691^{+0.102}_{-0.103}$, $\alpha_{\parallel}=0.987^{+0.057}_{-0.054}$, and $\alpha_{\perp}=1.002^{+0.034}_{-0.033}$, along with cosmological parameters $H_0=71.16^{+5.09}_{-5.50}$, $\Omega_m=0.276^{+0.086}_{-0.067}$, and $w_0=-0.971^{+0.236}_{-0.380}$; the joint analysis yields FoM improvements of roughly $30\%$ over GC-only constraints and constrains the mean optical depth $\log \bar{\tau}=-4.22\pm0.09$. This establishes kSZ as a complementary cosmological observable with real data and points to substantial gains for future surveys (DESI, PFS, Euclid, CSST, SO, CMB-S4) and EFT-based analyses. The results demonstrate the feasibility and value of jointly modeling GC and kSZ signals, including Alcock–Paczyński distortions and a nonlinear perturbation theory framework, to simultaneously constrain cosmology and baryonic gas properties around galaxies and halos.

Abstract

We perform the first joint analysis of the galaxy clustering (GC) and the kinetic Sunyaev-Zel'dovich (kSZ) effect to simultaneously constrain cosmological and astrophysical parameters in this work, utilizing a combination of the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) map and the Constant Stellar Mass (CMASS) galaxy sample. As a complementary probe to the galaxy density power spectrum, we incorporate the pairwise kSZ power spectrum detected with a high signal-to-noise ratio (S/N $\sim 7$) to derive constraints on cosmological parameters ($H_0 = 71.16^{+5.09}_{-5.50}$, $Ω_{\rm m} = 0.276^{+0.086}_{-0.067}$, $w_0 = -0.971^{+0.236}_{-0.380}$) and the average optical depth of the galaxy sample ($\lg\barτ = -4.22 \pm +0.09$). Compared to the GC-only analysis, the joint analysis yields tighter constraints on these cosmological parameters: the Figures of Merits (FoMs) improve by 29.3%, 32.3% and 21.5% for the $H_0$--$Ω_{\rm m}$, $H_0$--$w_0$ and $Ω_{\rm m}$--$w_0$ contours. For the first time, we demonstrate the complementary applicability of the kSZ effect in constrain cosmological parameters from real observational data.

Figures (3)

• Figure 1: The sky coverage of ACT map and CMASS galaxies with $N_{\rm side}=256$ in the HEALPix grid frame Gorski2005. The yellow area represents the overlapping region between two data sets selected and used in this work. The purple ones are galaxies that have been removed due to masking. The blue and green pixels respectively represent the remaining CMASS and ACT data.
• Figure 2: Results of CMASS + ACT analysis. Upper left: Multipoles of the galaxy density power spectrum. Dashed lines indicate the best-fit model by fitting the galaxy multipoles alone, while solid lines show the results from the joint analysis. Lower left: The kSZ power spectrum dipole along with the best-fitted model from the joint analysis (solid line). The covariance matrices of these power spectra are computed using a jackknife resampling method. The signal-to-noise ratio (S/N) of this kSZ dipole is estimated to be $\sim$7, as detailed in Appendix \ref{['app:method']}. Right: Posterior distributions of the cosmological observables. Blue solid contours correspond to results of the joint analysis, and red contours represent the constraints from galaxy multipoles only. The black vertical lines mark the fiducial values: $f=\Omega^{\rm fid}_{\rm m}(z_{\rm eff})^{0.55}$, $\alpha_\parallel=1$ and $\alpha_\perp=1$, where $\Omega^{\rm fid}_{\rm m}(z_{\rm eff})$ is the matter density at the effective redshift $z_{\rm eff}$, based on the fiducial cosmology.
• Figure 3: Similar to the right panel of Figure \ref{['fig:CMASS']}, but for the cosmological parameters $H_0$, $\Omega_{\rm m}$ and $w_0$.