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Register a new userThe Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Large-scale Structure Catalogs for Cosmological Analysis
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We present large-scale structure catalogs from the completed extended Baryon Oscillation Spectroscopic Survey (eBOSS). Derived from Sloan Digital Sky Survey (SDSS) -IV Data Release 16 (DR16), these catalogs provide the data samples, corrected for observational systematics, and random positions sampling the survey selection function. Combined, they allow large-scale clustering measurements suitable for testing cosmological models. We describe the methods used to create these catalogs for the eBOSS DR16 Luminous Red Galaxy (LRG) and Quasar samples. The quasar catalog contains 343,708 redshifts with $0.8 < z < 2.2$ over 4,808,deg$^2$. We combine 174,816 eBOSS LRG redshifts over 4,242,deg$^2$ in the redshift interval $0.6 < z < 1.0$ with SDSS-III BOSS LRGs in the same redshift range to produce a combined sample of 377,458 galaxy redshifts distributed over 9,493,deg$^2$. Improved algorithms for estimating redshifts allow that 98 per cent of LRG observations result in a successful redshift, with less than one per cent catastrophic failures ($Delta z > 1000$ ${rm km~s}^{-1}$). For quasars, these rates are 95 and 2 per cent (with $Delta z > 3000$ ${rm km~s}^{-1}$). We apply corrections for trends between the number densities of our samples and the properties of the imaging and spectroscopic data. For example, the quasar catalog obtains a $chi^2$/DoF$= 776/10$ for a null test against imaging depth before corrections and a $chi^2$/DoF$=6/8$ after. The catalogs, combined with careful consideration of the details of their construction found here-in, allow companion papers to present cosmological results with negligible impact from observational systematic uncertainties.
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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 present a measurement of baryonic acoustic oscillations (BAO) from Lyman-$alpha$ (Ly$alpha$) absorption and quasars at an effective redshift $z=2.33$ using the complete extended Baryonic Oscillation Spectroscopic Survey (eBOSS). The sixteenth and final eBOSS data release (SDSS DR16) contains all data from eBOSS and its predecessor, the Baryonic Oscillation Spectroscopic Survey (BOSS), providing $210,005$ quasars with $z_{q}>2.10$ that are used to measure Ly$alpha$ absorption. We measure the BAO scale both in the auto-correlation of Ly$alpha$ absorption and in its cross correlation with $341,468$ quasars with redshift $z_{q}>1.77$. Apart from the statistical gain from new quasars and deeper observations, the main improvements over previous work come from more accurate modeling of physical and instrumental correlations and the use of new sets of mock data. Combining the BAO measurement from the auto- and cross-correlation yields the constraints of the two ratios $D_{H}(z=2.33)/r_{d} = 8.99 pm 0.19$ and $D_{M}(z=2.33)/r_{d} = 37.5 pm 1.1$, where the error bars are statistical. These results are within $1.5sigma$ of the prediction of the flat-$Lambda$CDM cosmology of Planck~(2016). The analysis code, texttt{picca}, the catalog of the flux-transmission field measurements, and the $Delta chi^{2}$ surfaces are publicly available.
We present a void clustering analysis in configuration-space using the completed Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) DR16 samples. These samples consist of Luminous Red Galaxies (LRG) combined with the high redshift tail of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) DR12 CMASS galaxies (called as LRG+CMASS sample), Emission Line Galaxies (ELG) and quasars (QSO). We build void catalogues from the three eBOSS DR16 samples using a ZOBOV-based algorithm, providing 2,814 voids, 1,801 voids and 4,347 voids in the LRG+CMASS, ELG and QSO samples, respectively, spanning the redshift range $0.6<z<2.2$. We measure the redshift space distortions (RSD) around voids using the anisotropic void-galaxy cross-correlation function and we extract the distortion parameter $beta$. We test the methodology on realistic simulations before applying it to the data, and we investigate all our systematic errors on these mocks. We find $beta^{rm LRG}(z=0.74)=0.415pm0.087$, $beta^{rm ELG}(z=0.85)=0.665pm0.125$ and $beta^{rm QSO}(z=1.48)=0.313pm0.134$, for the LRG+CMASS, ELG and QSO sample, respectively. The quoted errors include systematic and statistical contributions. In order to convert our measurements in terms of the growth rate $fsigma_8$, we use consensus values of linear bias from the eBOSS DR16 companion papers~citep{eBOSScosmo}, resulting in the following constraints: $fsigma_8(z=0.74)=0.50pm0.11$, $fsigma_8(z=0.85)=0.52pm0.10$ and $fsigma_8(z=1.48)=0.30pm0.13$. Our measurements are consistent with other measurements from eBOSS DR16 using conventional clustering techniques.
We present the characteristics of the Damped Lyman-$alpha$ (DLA) systems found in the data release DR16 of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey (SDSS). DLAs were identified using the convolutional neural network (CNN) of~cite{Parks2018}. A total of 117,458 absorber candidates were found with $2 leq zdla leq 5.5$ and $19.7 leq lognhi leq 22$, including 57,136 DLA candidates with $lognhi geq 20.3$. Mock quasar spectra were used to estimate DLA detection efficiency and the purity of the resulting catalog. Restricting the quasar sample to bright forests, i.e. those with mean forest fluxes $meanflux>2timesfluxunit$, the completeness and purity are greater than 90% for DLAs with column densities in the range $20.1leq lognhi leq 22$.
The growth rate and expansion history of the Universe can be measured from large galaxy redshift surveys using the Alcock-Paczynski effect. We validate the Redshift Space Distortion models used in the final analysis of the Sloan Digital Sky Survey (SDSS) extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 16 quasar clustering sample, in configuration and Fourier space, using a series of HOD mock catalogues generated using the OuterRim N-body simulation. We test three models on a series of non-blind mocks, in the OuterRim cosmology, and blind mocks, which have been rescaled to new cosmologies, and investigate the effects of redshift smearing and catastrophic redshifts. We find that for the non-blind mocks, the models are able to recover $fsigma_8$ to within 3% and $alpha_parallel$ and $alpha_bot$ to within 1%. The scatter in the measurements is larger for the blind mocks, due to the assumption of an incorrect fiducial cosmology. From this mock challenge, we find that all three models perform well, with similar systematic errors on $fsigma_8$, $alpha_parallel$ and $alpha_bot$ at the level of $sigma_{fsigma_8}=0.013$, $sigma_{alpha_parallel}=0.012$ and $sigma_{alpha_bot}=0.008$. The systematic error on the combined consensus is $sigma_{fsigma_8}=0.011$, $sigma_{alpha_parallel}=0.008$ and $sigma_{alpha_bot}=0.005$, which is used in the final DR16 analysis. For BAO fits in configuration and Fourier space, we take conservative systematic errors of $sigma_{alpha_parallel}=0.010$ and $sigma_{alpha_bot}=0.007$.
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