DESI 2024 VII: Cosmological Constraints from the Full-Shape Modeling of Clustering Measurements (2411.12022v2)

Abstract: We present cosmological results from the measurement of clustering of galaxy, quasar and Lyman-$\alpha$ 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 $\Lambda$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 $\Omega_\mathrm{m}=0.2962\pm 0.0095$, and the amplitude of mass fluctuations to $\sigma_8=0.842\pm 0.034$. The addition of the cosmic microwave background (CMB) data tightens these constraints to $\Omega_\mathrm{m}=0.3056\pm 0.0049$ and $\sigma_8=0.8121\pm 0.0053$, 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 $\sum m_\nu < 0.071\,{\rm eV}$ at 95% confidence. DESI data alone measure the modified-gravity parameter that controls the clustering of massive particles, $\mu_0=0.11^{+0.45}_{-0.54}$, while the combination of DESI with the CMB and the clustering and lensing analysis from DESY3 constrains both modified-gravity parameters, giving $\mu_0 = 0.04\pm 0.22$ and $\Sigma_0 = 0.044\pm 0.047$, in agreement with general relativity. [Abridged.]

• The paper presents a novel full-shape clustering analysis of DESI’s first-year data that precisely constrains ΛCDM parameters (Ω_m = 0.2962±0.0095, σ_8 = 0.842±0.034).
• It employs redshift-space distortion and BAO measurements to improve neutrino mass limits, achieving m_ν < 0.409 eV with FS analysis and m_ν < 0.071 eV when combined with CMB data.
• The study explores dark energy dynamics and tests modified gravity, revealing a potential time-varying equation of state while validating general relativity predictions.

Cosmological Insights from DESI's First Year Clustering Measurements

The paper under examination provides a comprehensive analysis of the cosmological constraints derived from the Dark Energy Spectroscopic Instrument's (DESI) first year data release. By employing full-shape (FS) modeling of clustering measurements including redshift-space distortions, combined with the information from baryon acoustic oscillations (BAO), the paper establishes refined constraints on ΛCDM and explores extensions to this model.

The methodology harnessed by DESI includes an extensive analysis of power spectrum multipoles from spectroscopic data comprising galaxies, quasars, and the Lyman-α forest across redshifts of 0 < z < 4. This robust approach yields impactful constraints on cosmological parameters, with a particular emphasis on the matter density (Ω_m) and the amplitude of mass fluctuations (σ_8). DESI's full shape analysis coupled with BAO data provides a determination of Ω_m = 0.2962±0.0095 and σ_8 = 0.842±0.034, results which dovetail with constraints from other prevailing cosmological data including the Cosmic Microwave Background (CMB) and weak lensing.

A highlight of DESI's analysis is its demonstrable impact on neutrino physics within cosmology. The FS analysis alone sets a compelling upper limit on the sum of the neutrino masses to m_ν < 0.409 eV at 95% confidence, improving to m_ν < 0.071 eV when combined with CMB data. This represents a significant enhancement over previous constraints, showing the critical role of clustering data in elucidating neutrino properties.

In exploring cosmological models beyond ΛCDM, DESI data display a persisting preference for a time-varying dark energy equation of state (w_0, w_a model). The combination of full-shape analysis with BAO reveals a subtle preference for w_0 > -1 and w_a < 0, suggesting intrigues in the dark energy sector that merit further exploration. The paper cautiously notes the significance, ranging up to 3.8σ with different SN Ia datasets, indicating a potential departure from the canonical cosmological constant.

Modified gravity treaties are also addressed through the paper of the parameters µ_0 and Σ_0, with DESI data providing validation for general relativity. DESI's constraint on modified gravity affirms that the clustering signal, influential to the growth of structure, is consistent with GR predictions. This has been enhanced when combined with external datasets, exemplifying DESI's role in alleviating discrepancies observed in earlier datasets.

The implications of these findings denote upcoming avenues in AI-driven cosmological simulations that could emulate DESI's methodology to further nuance large-scale structures and underpin the micro-physical interactions in cosmology. Future surveys expanding on DESI's framework will benefit from the precise calibration offered by this first year analysis, informing both the theoretical models and practical embodiments of observational cosmology.

In conclusion, the DESI 2024 examinations into full-shape clustering deliver not only reinforced measurements of key cosmological parameters but also open dialogues in dark energy dynamics, neutrino mass constraints, and tests of gravity—each a cornerstone for future cosmological research and AI-enhanced analytic techniques.