The completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Large-scale Structure Catalogues and Measurement of the isotropic BAO between redshift 0.6 and 1.1 for the Emission Line Galaxy Sample (2007.09007v1)

Abstract: We present the Emission Line Galaxy (ELG) sample of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) from the Sloan Digital Sky Survey IV Data Release 16 (DR16). After describing the observations and redshift measurement for the 269,243 observed ELG spectra over 1170 deg$^2$, we present the large-scale structure catalogues, which are used for the cosmological analysis. These catalogues contain 173,736 reliable spectroscopic redshifts between 0.6 and 1.1, along with the associated random catalogues quantifying the extent of observations, and the appropriate weights to correct for non-cosmological fluctuations. We perform a spherically averaged baryon acoustic oscillations (BAO) measurement in configuration space, with density field reconstruction: the data 2-point correlation function shows a feature consistent with that of the BAO, providing a 3.2-percent measurement of the spherically averaged BAO distance $D_V(z_{\rm eff})/r_{\rm drag} = 18.23\pm 0.58$ at the effective redshift $z_{\rm eff}=0.845$.

Overview of the SDSS-IV eBOSS DR16 ELG LSS and Isotropic BAO Paper

The paper discusses the completion of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) from the Sloan Digital Sky Survey IV (SDSS-IV). Specifically, it focuses on the Emission Line Galaxy (ELG) sample from the Data Release 16 (DR16) and the analysis of large-scale structure (LSS) catalogues and measurements of isotropic Baryon Acoustic Oscillations (BAO) between redshifts 0.6 and 1.1. This paper is essential as it provides insights into the geometry of the Universe and constrains cosmological parameters using BAO as a standard ruler.

Key Components of the Study

1. Data and Observations:
   • The sample comprises 269,243 observed ELG spectra over an area of 1,170 square degrees, with reliable spectroscopic redshifts identified for 173,736 galaxies between redshifts 0.6 and 1.1.
   • The data were collected using the BOSS spectrograph, and advanced redshift fitting techniques were employed to improve the precision and accuracy of the measurements, highlighting a reduction in redshift failures and catastrophic errors.
2. Large-scale Structure Catalogues:
   • The paper includes the creation of LSS catalogues essential for cosmological analyses. These catalogues effectively correct for non-cosmological fluctuations using weights that account for observational systematics, including redshift failures due to low signal-to-noise ratios and dependencies on imaging depth.
3. Mock Catalogues:
   • The paper utilizes mock catalogues, such as the high-resolution N-body simulation OuterRim mocks and approximate EZmocks, to validate and perform BAO measurements. These simulations are critical in understanding and counterbalancing the various systematic effects that can affect the observations.
4. BAO Measurement:
   • Spherically averaged BAO measurements were performed using the two-point correlation function in configuration space. Reconstruction techniques were applied to partially remove non-linear effects, resulting in an accurate measurement of the BAO feature.
   • The paper reports a 3.2% measurement accuracy for the isotropic BAO distance $D_V(z_{\rm eff})/r_{\rm drag} = 18.23 \pm 0.58$ at an effective redshift of $z_{\rm eff}=0.845$.

Implications and Future Prospects

The results from the eBOSS DR16 ELG sample significantly enhance the precision of cosmological measurements, specifically extending the redshift range over which BAO measurements can be reliably made. The methodologies developed and employed in this analysis provide a solid foundation for forthcoming large-scale surveys such as DESI, PFS, Euclid, and WFIRST, which aim to map the Universe's expansion history and understand dark energy's role.

The paper contributes robust evidence towards the standard $\Lambda$CDM cosmological model, offering precise measurements of cosmological distances that align well with predictions from other high-precision cosmological observables. These results demonstrate the role of ELGs as effective tracers of the Universe's large-scale structure, further guiding future explorations in cosmic acceleration and structure formation.

These findings are part of a broader series presenting the final eBOSS DR16 data and cosmological implications, aiding significantly in the larger endeavor of unraveling the Universe's detailed expansion history.