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Register a new userThe Completed SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Growth rate of structure measurement from cosmic voids
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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.
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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 perform a joint BAO and RSD analysis using the eBOSS DR16 LRG and ELG samples in the redshift range of $zin[0.6,1.1]$, and detect a RSD signal from the cross power spectrum at a $sim4sigma$ confidence level, i.e., $fsigma_8=0.317pm0.080$ at $z_{rm eff}=0.77$. Based on the chained power spectrum, which is a new development in this work to mitigate the angular systematics, we measurement the BAO distances and growth rate simultaneously at two effective redshifts, namely, $D_{rm M}/r_{rm d} (z=0.70)=17.96pm0.51, D_{rm H}/r_{rm d} (z=0.70)=21.22pm1.20, fsigma_8 (z=0.70) =0.43pm0.05$, and $D_{rm M}/r_{rm d} (z=0.845)=18.90pm0.78, D_{rm H}/r_{rm d} (z=0.845)=20.91pm2.86, fsigma_8 (z=0.845) =0.30pm0.08$. Combined with BAO measurements including those from the eBOSS DR16 QSO and Lyman-$alpha$ sample, our measurement has raised the significance level of a nonzero $Omega_{rm Lambda}$ to $sim11sigma$.
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.
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 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 $20.1leq lognhi leq 22$.
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