DESI 2024 VII: Cosmological Constraints from the Full-Shape Modeling of Clustering Measurements

TL;DR

DESI DR1 employs full-shape clustering modeling of six tracers across six redshift bins to extract cosmological information beyond BAO. Using perturbation theory with a comprehensive set of nuisance parameters and external data from Planck, SN Ia, and DESY3, the study delivers percent-level constraints on Ω_m, σ_8, and H_0 within ΛCDM and probes extensions including time-varying dark energy, neutrino masses, and modified gravity. The FS+BAO results tighten cosmological parameters markedly when combined with CMB and DESY3, yielding ∑m_ν<0.071 eV (95%) and μ_0≈0.04±0.22, Σ_0≈0.044±0.047, both consistent with general relativity. The analysis also indicates a persistent, dataset-dependent preference for dynamical dark energy (w_0w_aCDM), with significant improvements in the dark-energy Figure of Merit when FS data are added to BAO+CMB+SN Ia. Overall, DESI FS demonstrates the power of growth information to sharpen cosmological inferences and set strong bounds on new physics, with Year-3 data expected to further tighten these constraints.

Abstract

We present cosmological results from the measurement of clustering of galaxy, quasar and Lyman-$α$ forest tracers from the first year of observations with the Dark Energy Spectroscopic Instrument (DESI Data Release 1). We adopt the full-shape (FS) modeling of the power spectrum, including the effects of redshift-space distortions, in an analysis which has been validated in a series of supporting papers. In the flat $Λ$CDM cosmological model, DESI (FS+BAO), combined with a baryon density prior from Big Bang Nucleosynthesis and a weak prior on the scalar spectral index, determines matter density to $Ω_\mathrm{m}=0.2962\pm 0.0095$, and the amplitude of mass fluctuations to $σ_8=0.842\pm 0.034$. The addition of the cosmic microwave background (CMB) data tightens these constraints to $Ω_\mathrm{m}=0.3056\pm 0.0049$ and $σ_8=0.8121\pm 0.0053$, while further addition of the the joint clustering and lensing analysis from the Dark Energy Survey Year-3 (DESY3) data leads to a 0.4% determination of the Hubble constant, $H_0 = (68.40\pm 0.27)\,{\rm km\,s^{-1}\,Mpc^{-1}}$. In models with a time-varying dark energy equation of state, combinations of DESI (FS+BAO) with CMB and type Ia supernovae continue to show the preference, previously found in the DESI DR1 BAO analysis, for $w_0>-1$ and $w_a<0$ with similar levels of significance. DESI data, in combination with the CMB, impose the upper limits on the sum of the neutrino masses of $\sum m_ν< 0.071\,{\rm eV}$ at 95% confidence. DESI data alone measure the modified-gravity parameter that controls the clustering of massive particles, $μ_0=0.11^{+0.45}_{-0.54}$, while the combination of DESI with the CMB and the clustering and lensing analysis from DESY3 constrains both modified-gravity parameters, giving $μ_0 = 0.04\pm 0.22$ and $Σ_0 = 0.044\pm 0.047$, in agreement with general relativity. [Abridged.]

Figures (10)

• Figure 1: 68% and 95% credible intervals in the $\Omega_\mathrm{m}$--$\sigma_8$ plane (left panel) and $\Omega_\mathrm{m}$--$H_0$ plane (right panel) from the combined DESI full-shape and BAO analysis, assuming the $\Lambda$CDM background. We show the constraints from individual DESI tracers (with the BBN and loose $n_\mathrm{s}$ priors), and the combined measurement that includes all the tracers shown and the Ly$\alpha$ BAO data.
• Figure 2: Constraints on the parameter $S_8\equiv \sigma_8 (\Omega_\mathrm{m}/0.3)^{0.5}$, assuming the $\Lambda$CDM background. The whisker on the bottom (and the corresponding blue-shaded region) shows our fiducial 68% constraint from DESI DR1 (FS+BAO), combined with the BBN and loose $n_\mathrm{s}$ priors. The first two whiskers from the top, in orange, show the constraints from the CMB, without and with CMB lensing information. The following four whiskers, in green, show the results from weak lensing probes, while the second to bottom whisker, in blue, shows the constraints from the SDSS combination of redshift-space distortions and BAO. See text for details.
• Figure 3: Projected constraints on $\Omega_\mathrm{m}$, $\sigma_8$, and $S_8$ in the $\Lambda$CDM model, with 68% and 95% credible intervals shown in each case. The blue contours display the DESI (FS+BAO) constraints (with the BBN and loose $n_\mathrm{s}$ priors). The orange contours show constraints from the DESY3 ($6\times 2$-pt) analysis which combines galaxy clustering, cosmic shear and CMB lensing. The green contours show the combination of DESI and DESY3 ($6\times 2$-pt) data. For comparison we also show the CMB temperature and polarisation constraints without the lensing reconstruction as purple contours.
• Figure 4: Constraints projected to the $\Omega_\mathrm{m}$--$\sigma_8$ plane in the $\Lambda$CDM model. The green contour shows constraints from the DESI full shape and BAO analysis, combined with the BBN and $n_\mathrm{s10}$ priors, and further complemented with the DESY3 ($6\times 2$-pt) data. The pink contour shows the CMB without lensing reconstruction. The brown contour shows the combination of the two, that is, DESI combined with DESY3 ($6\times 2$-pt) and CMB-nl.
• Figure 5: Constraints on $w_0$ and $w_a$, assuming a $w_0w_a$CDM model with a time-varying dark energy equation of state parameterisation (\ref{['eq:DE_EoS']}). The contours represent the 68% and 95% credible intervals. The solid blue, orange, and green contours represent the combination of DESI (FS+BAO) and CMB with three respective SN Ia data sets: PantheonPlus, Union3 and DES-SN5YR. The dashed blue, orange, and green contours show the same respective combinations, but with the DESI full-shape clustering and BAO replaced by DESI (BAO). The figure shows how the addition of the full-shape information to the BAO-only data improves the precision of the constraints. The measurements of these two parameters remain mutually consistent, and prefer $w_0 > -1$ and $w_a < 0$.