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Register a new userThe completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: geometry and growth from the anisotropic void-galaxy correlation function in the luminous red galaxy sample
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We present an analysis of the anisotropic redshift-space void-galaxy correlation in configuration space using the Sloan Digital Sky Survey extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 16 luminous red galaxy (LRG) sample. This sample consists of LRGs between redshifts 0.6 and 1.0, combined with the high redshift $z>0.6$ tail of the Baryon Oscillation Spectroscopic Survey Data Release 12 CMASS sample. We use a reconstruction method to undo redshift-space distortion (RSD) effects from the galaxy field before applying a watershed void-finding algorithm to remove bias from the void selection. We then perform a joint fit to the multipole moments of the correlation function for the growth rate $fsigma_8$ and the geometrical distance ratio $D_M/D_H$, finding $fsigma_8(z_mathrm{eff})=0.356pm0.079$ and $D_M/D_H(z_mathrm{eff})=0.868pm0.017$ at the effective redshift $z_mathrm{eff}=0.69$ of the sample. The posterior parameter degeneracies are orthogonal to those from galaxy clustering analyses applied to the same data, and the constraint achieved on $D_M/D_H$ is significantly tighter. In combination with the consensus galaxy BAO and full-shape analyses of the same sample, we obtain $fsigma_8=0.447pm0.039$, $D_M/r_d=17.48pm0.23$ and $D_H/r_d=20.10pm0.34$. These values are in good agreement with the $Lambda$CDM model predictions and represent reductions in the uncertainties of $13%$, $23%$ and $28%$ respectively compared to the combined results from galaxy clustering, or an overall reduction of 55% in the allowed volume of parameter space.
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We present the cosmological analysis of the configuration-space anisotropic clustering in the completed Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) DR16 galaxy sample. This sample consists of luminous red galaxies (LRGs) spanning the redshift range $0.6 < z < 1$, at an effective redshift of $z_{rm eff}=0.698$. It combines 174 816 eBOSS LRGs and 202 642 BOSS CMASS galaxies. We extract and model the baryon acoustic oscillations (BAO) and redshift-space distortions (RSD) features from the galaxy two-point correlation function to infer geometrical and dynamical cosmological constraints. The adopted methodology is extensively tested on a set of realistic simulations. The correlations between the inferred parameters from the BAO and full-shape correlation function analyses are estimated. This allows us to derive joint constraints on the three cosmological parameter combinations: $D_M(z)/r_d$, $D_H(z)/r_d$ and $fsigma_8(z)$, where $D_M$ is the comoving angular diameter distance, $D_H$ is Hubble distance, $r_d$ is the comoving BAO scale, $f$ is the linear growth rate of structure, and $sigma_8$ is the amplitude of linear matter perturbations. After combining the results with those from the parallel power spectrum analysis of Gil-Marin et al. 2020, we obtain the constraints: $D_M/r_d = 17.65 pm 0.30$, $D_H/r_d = 19.77 pm 0.47$, $fsigma_8 = 0.473 pm 0.044$. These measurements are consistent with a flat $Lambda$CDM model with standard gravity.
We measure the small-scale clustering of the Data Release 16 extended Baryon Oscillation Spectroscopic Survey Luminous Red Galaxy sample, corrected for fibre-collisions using Pairwise Inverse Probability weights, which give unbiased clustering measurements on all scales. We fit to the monopole and quadrupole moments and to the projected correlation function over the separation range $7-60,h^{-1}$Mpc with a model based on the Aemulus cosmological emulator to measure the growth rate of cosmic structure, parameterized by $fsigma_8$. We obtain a measurement of $fsigma_8(z=0.737)=0.408pm0.038$, which is $1.4sigma$ lower than the value expected from 2018 Planck data for a flat $Lambda$CDM model, and is more consistent with recent weak-lensing measurements. The level of precision achieved is 1.7 times better than more standard measurements made using only the large-scale modes of the same sample. We also fit to the data using the full range of scales $0.1-60,h^{-1}$Mpc modelled by the Aemulus cosmological emulator and find a $4.5sigma$ tension in the amplitude of the halo velocity field with the Planck+$Lambda$CDM model, driven by a mismatch on the non-linear scales. This may not be cosmological in origin, and could be due to a breakdown in the Halo Occupation Distribution model used in the emulator. Finally, we perform a robust analysis of possible sources of systematics, including the effects of redshift uncertainty and incompleteness due to target selection that were not included in previous analyses fitting to clustering measurements on small scales.
We present 2000 mock galaxy catalogs for the analysis of baryon acoustic oscillations in the Emission Line Galaxy (ELG) sample of the Extended Baryon Oscillation Spectroscopic Survey Data Release 16 (eBOSS DR16). Each mock catalog has a number density of $6.7 times 10^{-4} h^3 rm Mpc^{-3}$, covering a redshift range from 0.6 to 1.1. The mocks are calibrated to small-scale eBOSS ELG clustering measurements at scales of around 10 $h^{-1}$Mpc. The mock catalogs are generated using a combination of GaLAxy Mocks (GLAM) simulations and the Quick Particle-Mesh (QPM) method. GLAM simulations are used to generate the density field, which is then assigned dark matter halos using the QPM method. Halos are populated with galaxies using a halo occupation distribution (HOD). The resulting mocks match the survey geometry and selection function of the data, and have slightly higher number density which allows room for systematic analysis. The large-scale clustering of mocks at the baryon acoustic oscillation (BAO) scale is consistent with data and we present the correlation matrix of the mocks.
We analyse the clustering of the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 16 luminous red galaxy sample (DR16 eBOSS LRG) in combination with the high redshift tail of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 12 (DR12 BOSS CMASS). We measure the redshift space distortions (RSD) and also extract the longitudinal and transverse baryonic acoustic oscillation (BAO) scale from the anisotropic power spectrum signal inferred from 377,458 galaxies between redshifts 0.6 and 1.0, with effective redshift of $z_{rm eff}=0.698$ and effective comoving volume of $2.72,{rm Gpc}^3$. After applying reconstruction we measure the BAO scale and infer $D_H(z_{rm eff})/r_{rm drag} = 19.30pm 0.56$ and $D_M(z_{rm eff})/r_{rm drag} =17.86 pm 0.37$. When we perform a redshift space distortions analysis on the pre-reconstructed catalogue on the monopole, quadrupole and hexadecapole we find, $D_H(z_{rm eff})/r_{rm drag} = 20.18pm 0.78$, $D_M(z_{rm eff})/r_{rm drag} =17.49 pm 0.52$ and $fsigma_8(z_{rm eff})=0.454pm0.046$. We combine both sets of results along with the measurements in configuration space of cite{LRG_corr} and report the following consensus values: $D_H(z_{rm eff})/r_{rm drag} = 19.77pm 0.47$, $D_M(z_{rm eff})/r_{rm drag} = 17.65pm 0.30$ and $fsigma_8(z_{rm eff})=0.473pm 0.044$, which are in full agreement with the standard $Lambda$CDM and GR predictions. These results represent the most precise measurements within the redshift range $0.6leq z leq 1.0$ and are the culmination of more than 8 years of SDSS observations.
We describe the algorithm used to select the Luminous Red Galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-Field Infrared Survey Explorer (WISE). LRG targets are required to meet a set of color selection criteria and have z-band and i-band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (median redshift 0.71). We demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least 89% of the target sample yields secure redshift measurements. We also present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reached.
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