Tomographic Alcock–Paczyński Test with Redshift-space Correlation Function: Evidence for the Dark Energy Equation-of-state Parameter w > −1

Abstract

The apparent shape of galaxy clustering depends on the adopted cosmology used to convert observed redshift to comoving distance, the r(z) relation, as it changes the line elements along and across the line of sight differently. The Alcock–Paczyński (AP) test exploits this property to constrain the expansion history of the universe. We present an extensive review of past studies on the AP test. We adopt an extended AP test method introduced by Park et al., which uses the full shape of redshift-space two-point correlation function (CF) as the standard shape, and apply it to the Sloan Digital Sky Survey DR7, BOSS, and eBOSS LRG samples covering the redshift range up to z = 0.8. We calibrate the test against the nonlinear cosmology-dependent systematic evolution of the CF shape using Multiverse simulations. We focus on examining whether or not the flat Lambda cold dark matter (ΛCDM) concordance model is consistent with observation. We constrain the flat wCDM model to have w = − 0.892 − 0.050 + 0.045 and Ω m = 0.282 − 0.023 + 0.024 from our AP test alone, which is significantly tighter than the constraints from the BAO or SNe Ia methods by a factor of 3–6. When the AP test result is combined with the recent BAO and SNe Ia results, we obtain w = − 0.903 − 0.023 + 0.023 and Ω m = 0.285 − 0.009 + 0.014 . This puts a strong tension with the flat ΛCDM model with w = −1 at the 4.2σ level. Consistency with w = −1 is obtained only when the Planck cosmic microwave background (CMB) observation is combined. It remains to be seen whether this tension between observations of galaxy distribution at low redshifts and CMB anisotropy at the decoupling epoch becomes greater in future studies and leads us to a new paradigm of cosmology.

The One-hundred-deg2 DECam Imaging in Narrowbands (ODIN): Survey Design and Science Goals

“…Another possibility is to use the shape of the two-point correlation function and apply the extended Alcock-Paczynski test (Park et al 2019;Dong et al 2023) to the ODIN data. As the shape of the two-point correlation function of cosmic objects is insensitive to the growth of structure and their bias, it is a good "standard shape" and can be used to measure the expansion history of the universe.…”

“…As the shape of the two-point correlation function of cosmic objects is insensitive to the growth of structure and their bias, it is a good "standard shape" and can be used to measure the expansion history of the universe. Recently, the method has been applied to the low-redshift SDSS survey data, and a tight constraint on the dark energy equation of state parameter w = − 0.903 ± 0.023 was obtained for a flat wCDM universe, which is 4.2σ away from the ΛCDM model (Dong et al 2023). The analysis can be applied to the higher redshift universe revealed by ODIN, to explore the possibility of potential nonstandard dark energy signatures, and more generally test if the observed universe is consistent with a decelerating epoch as predicted by the current standard cosmology.…”