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Cosmology in Extended Parameter Space with DESI Data Release 2 Baryon Acoustic Oscillations: A 2$σ$+ Detection of Nonzero Neutrino Masses with an Update on Dynamical Dark Energy and Lensing Anomaly

Shouvik Roy Choudhury

Abstract

We obtain constraints in a 12 parameter cosmological model using the recent Dark Energy Spectroscopic Instrument Data Release (DR) 2 Baryon Acoustic Oscillations (BAO) data, combined with cosmic microwave background (CMB) power spectra (Planck Public Release, PR, 4) and lensing (Planck PR4 + Atacama Cosmology Telescope (ACT) Data Release (DR) 6) data, uncalibrated Type Ia Supernovae (SNe) data from Pantheon+ and Dark Energy Survey (DES) Year 5 (DESY5) samples, and Weak Lensing (WL: DES Year 1) data. The cosmological model consists of six $Λ$CDM parameters, and additionally, the dynamical dark energy parameters ($w_0$, $w_a$), the sum of neutrino masses ($\sum m_ν$), the effective number of non-photon radiation species ($N_{\rm eff}$), the scaling of the lensing amplitude ($A_{\rm lens}$), and the running of the scalar spectral index ($α_s$). Our major findings are the following: i) With CMB+BAO+DESY5+WL, we obtain the first 2$σ$+ detection of a nonzero $\sum m_ν = 0.19^{+0.15}_{-0.18}$ eV (95%). Replacing DESY5 with Pantheon+ still yields a $\sim$1.9$σ$ detection. ii) The cosmological constant lies at the edge of the 95% contour with CMB+BAO+Pantheon+, but is excluded at 2$σ$+ with DESY5, leaving evidence for dynamical dark energy dataset-dependent and inconclusive. iii) With CMB+BAO+SNe+WL, $A_{\rm lens} = 1$ is excluded at $>2σ$, while it remains consistent with unity without WL data - suggesting that the existence of lensing anomaly with Planck PR4 likelihoods may depend on non-CMB datasets. iv) The Hubble tension persists at 3.6-4.2$σ$ with CMB+BAO+SNe; WL data has minimal impact.

Cosmology in Extended Parameter Space with DESI Data Release 2 Baryon Acoustic Oscillations: A 2$σ$+ Detection of Nonzero Neutrino Masses with an Update on Dynamical Dark Energy and Lensing Anomaly

Abstract

We obtain constraints in a 12 parameter cosmological model using the recent Dark Energy Spectroscopic Instrument Data Release (DR) 2 Baryon Acoustic Oscillations (BAO) data, combined with cosmic microwave background (CMB) power spectra (Planck Public Release, PR, 4) and lensing (Planck PR4 + Atacama Cosmology Telescope (ACT) Data Release (DR) 6) data, uncalibrated Type Ia Supernovae (SNe) data from Pantheon+ and Dark Energy Survey (DES) Year 5 (DESY5) samples, and Weak Lensing (WL: DES Year 1) data. The cosmological model consists of six CDM parameters, and additionally, the dynamical dark energy parameters (, ), the sum of neutrino masses (), the effective number of non-photon radiation species (), the scaling of the lensing amplitude (), and the running of the scalar spectral index (). Our major findings are the following: i) With CMB+BAO+DESY5+WL, we obtain the first 2+ detection of a nonzero eV (95%). Replacing DESY5 with Pantheon+ still yields a 1.9 detection. ii) The cosmological constant lies at the edge of the 95% contour with CMB+BAO+Pantheon+, but is excluded at 2+ with DESY5, leaving evidence for dynamical dark energy dataset-dependent and inconclusive. iii) With CMB+BAO+SNe+WL, is excluded at , while it remains consistent with unity without WL data - suggesting that the existence of lensing anomaly with Planck PR4 likelihoods may depend on non-CMB datasets. iv) The Hubble tension persists at 3.6-4.2 with CMB+BAO+SNe; WL data has minimal impact.

Paper Structure

This paper contains 11 sections, 2 equations, 6 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Analysis methodology
  3. Cosmological model and parameter sampling
  4. Datasets
  5. Numerical results
  6. $w_{0,\rm DE}$ and $w_{a,\rm DE}$
  7. $\sum m_{\nu}$
  8. $\Omega_m$ and $S_8$
  9. $A_{\rm lens}$
  10. $N_{\rm eff}$ and $H_0$
  11. Conclusions

Figures (6)

  • Figure 1: 68% and 95% marginalised contours in the $w_{0,\rm DE} - w_{a,\rm DE}$ plane for different data combinations. The area to the right of the vertical dashed blue line and above the slanted dashed blue line represents the parameter space corresponding to quintessence-like or non-phantom dark energy.
  • Figure 2: A comparison of the 1D marginalized posterior distributions for $\sum m_{\nu}$ [eV] across various data combinations. The panel in the right shows results with the DES Year 1 Weak Lensing data (WL) included. Note that in the right panel, the Planck PR4+lensing+DESI2+DESY5+WL dataset combination leads to a 2$\sigma$+ detection of non-zero $\sum m_{\nu}$. The two vertical black dashed lines (in both panels) indicate the minimum mass thresholds for the normal (0.057 eV) and inverted (0.096 eV) neutrino mass hierarchies, respectively.
  • Figure 3: A comparison of the 2D correlation plots between $\sum m_{\nu}$ [eV] and various other parameters across various data combinations.
  • Figure 4: A comparison of the 1D marginalized posterior distributions for $\Omega_m$ and $S_8$ across various data combinations. Note that the $\Omega_m$ posteriors remain similar with the addition of WL data, but the $S_8$ values are lowered.
  • Figure 5: The left panel shows the 1D posterior distributions of $A_{\rm lens}$ for various data combinations. The right panel shows its 2D correlation plots with the $S_8$ parameter. We note that dataset combinations with WL included leads to a 2$\sigma$+ lensing anomaly due to the strong correlation with $S_8$.
  • ...and 1 more figures