Completed SDSSIV 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 Ly α forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in largescale structure. These experiments, composed of data from SDSS, SDSSII, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angulardiameter distances and Hubble distances relative to the sound horizon, r_{d}, from eight different samples and six measurements of the growth rate parameter, f σ_{8}, from redshiftspace 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 darkenergyfree models at more than eight standard deviations in an extension to the flat, Λ CDM 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 Λ CDM cosmological model when combined with Planck measurements. The combined BAO and RSD measurements indicate σ_{8}=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 multipleparameter extensions remain consistent with a Λ CDM model. Regardless of cosmological model, the precision on each of the three parameters, Ω_{Λ}, H_{0}, and σ_{8}, 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 timeevolving equation of state for dark energy, the combined samples produce a constraint Ω_{k}=0.0022 ±0.0022 . The dark energy constraints lead to w_{0}=0.909 ±0.081 and w_{a}=0.4 9_{0.30}^{+0.35}, corresponding to an equation of state of w_{p}=1.018 ±0.032 at a pivot redshift z_{p}=0.29 and a Dark Energy Task Force Figure of Merit of 94. The inverse distance ladder measurement under this model yields H_{0}=68.18 ±0.79 km s^{1} Mpc^{1} , 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_{0} that are independent of the CMB data, with similar central values and precision under a Λ CDM model. Our most constraining combination of data gives the upper limit on the sum of neutrino masses at ∑m_{ν}<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 20002010. We compute the relative gain across the five dimensions spanned by w , Ω_{k}, ∑m_{ν}, H_{0}, and σ_{8} and find that the SDSS BAO and RSD data reduce the total posterior volume by a factor of 40 relative to the previous generation. Adding again the Planck, DES, and Pantheon SN Ia samples leads to an overall contraction in the fivedimensional posterior volume of 3 orders of magnitude.
 Publication:

Physical Review D
 Pub Date:
 April 2021
 DOI:
 10.1103/PhysRevD.103.083533
 arXiv:
 arXiv:2007.08991
 Bibcode:
 2021PhRvD.103h3533A
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 A summary of all SDSS BAO and RSD measurements with accompanying legacy figures can be found here: https://www.sdss.org/science/finalbaoandrsdmeasurements/ . The full cosmological interpretation of these measurements can be found here: https://www.sdss.org/science/cosmologyresultsfromeboss/