Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory

Abstract

We present the cosmological implications from final measurements of clustering using galaxies, quasars, and Lyα forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in large-scale structure. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, r<sub>d</sub>, from eight different samples and six measurements of the growth rate parameter, fσ<sub>8</sub>, from redshift-space distortions (RSD). This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, ΛCDM model that allows for curvature. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization, under the same model, the BAO data provide nearly an order of magnitude improvement on curvature constraints relative to primary CMB constraints alone. Independent of distance measurements, the SDSS RSD data complement weak lensing measurements from the Dark Energy Survey (DES) in demonstrating a preference for a flat ΛCDM cosmological model when combined with Planck measurements. The combined BAO and RSD measurements indicate σ<sub>8</sub>=0.85±0.03, implying a growth rate that is consistent with predictions from Planck temperature and polarization data and with General Relativity. When combining the results of SDSS BAO and RSD, Planck, Pantheon Type Ia supernovae (SNe Ia), and DES weak lensing and clustering measurements, all multiple-parameter extensions remain consistent with a ΛCDM model. Regardless of cosmological model, the precision on each of the three parameters, Ω<sup>Λ</sup>, H<sub>0</sub>, and σ<sub>8</sub>, remains at roughly 1%, showing changes of less than 0.6% in the central values between models. In a model that allows for free curvature and a time-evolving equation of state for dark energy, the combined samples produce a constraint Ω<sup>K</sup>=-0.0022±0.0022. The dark energy constraints lead to w<sub>0</sub>=-0.909±0.081 and w<sub>a</sub>=$-0.49_{-0.30}^{+0.35}$, corresponding to an equation of state of w<sub>p</sub>=-1.018±0.032 at a pivot redshift z<sub>p</sub>=0.29 and a Dark Energy Task Force Figure of Merit of 94. The inverse distance ladder measurement under this model yields H<sub>0</sub>=68.18±0.79 km s<sup>-1</sup> Mpc<sup>-1</sup>, remaining in tension with several direct determination methods; the BAO data allow Hubble constant estimates that are robust against the assumption of the cosmological model. In addition, the BAO data allow estimates of H<sub>0</sub> that are independent of the CMB data, with similar central values and precision under a ΛCDM model. Our most constraining combination of data gives the upper limit on the sum of neutrino masses at Σm<sub>ν</sub><0.115 eV (95% confidence). Finally, we consider the improvements in cosmology constraints over the last decade by comparing our results to a sample representative of the period 2000-2010. We compute the relative gain across the five dimensions spanned by w, Ω<sub>k</sub>, Σm<sub>ν</sub>, H<sub>0</sub>, and σ<sub>8</sub> and find that the SDSS BAO and RSD data reduce the total posterior volume by a factor of 40 relative to the previous generation. Finally, adding again the Planck, DES, and Pantheon SN Ia samples leads to an overall contraction in the five-dimensional posterior volume of 3 orders of magnitude.

Keywords

Affiliated Institutions

• Université Paris Cité FR
• University of Wisconsin–Madison US
• NSF NOIRLab US
• Haverford College US
• University of Utah US
• Institut National de Physique Nucléaire et de Physique des Particules FR
• Sorbonne Université FR
• Brookhaven National Laboratory US
• California Institute of Technology US
• Kavli Institute for Particle Astrophysics and Cosmology US
• Aix-Marseille Université FR
• University College London GB
• Laboratoire de Physique Nucléaire et de Hautes Énergies FR
• University of Toronto CA
• Swinburne University of Technology AU
• Universidad Nacional Autónoma de México MX
• Fermi National Accelerator Laboratory US
• Institute for High Energy Physics ES
• CEA Paris-Saclay FR
• University of Edinburgh GB
• Universidad Autónoma de Madrid ES
• Centre National de la Recherche Scientifique FR
• Perimeter Institute CA
• Sejong University KR
• Chinese Academy of Sciences CN
• Canadian Institute for Theoretical Astrophysics CA
• Pennsylvania State University US
• University of St Andrews GB
• University of Cape Town ZA
• New Mexico State University US
• Universidad de Guanajuato MX
• Universitat de Barcelona ES
• Université Paris-Saclay FR
• Durham University GB
• Commissariat à l'Énergie Atomique et aux Énergies Alternatives FR
• University of Wyoming US
• Lawrence Berkeley National Laboratory US
• Liverpool John Moores University GB
• Secretaría de Ciencia, Humanidades, Tecnología e Innovación MX
• Texas Christian University US
• University of Oxford GB
• Ohio University US
• Korea University of Science and Technology KR
• École Polytechnique Fédérale de Lausanne CH
• University of Pittsburgh US
• University of Waterloo CA
• National Astronomical Observatories CN
• Institut de Recherche sur les Lois Fondamentales de l'Univers FR
• Korea Astronomy and Space Science Institute KR
• Institut d'Astrophysique de Paris FR
• The Ohio State University US
• New York University US
• Max Planck Institute for Extraterrestrial Physics DE
• University of Washington US
• University of Portsmouth GB
• South African Radio Astronomy Observatory ZA
• Lomonosov Moscow State University RU

Related Publications