The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: a tomographic measurement of cosmic structure growth and expansion rate based on optimal redshift weights (1801.03043v3)

Abstract: We develop a new method, which is based on the optimal redshift weighting scheme, to extract the maximal tomographic information of baryonic acoustic oscillations (BAO) and redshift space distortions (RSD) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 14 quasar (DR14Q) survey. We validate our method using the EZ mocks, and apply our pipeline to the eBOSS DR14Q sample in the redshift range of $0.8<z<2.2$. We report a joint measurement of $f\sigma_8$ and two-dimensional BAO parameters $D_{\rm A}$ and $H$ at four effective redshifts of $z_{\rm eff}=0.98, 1.23, 1.52$ and $1.94$, and provide the full data covariance matrix. Using our measurement combined with BOSS DR12, MGS and 6dFGS BAO measurements, we find that the existence of dark energy is supported by observations at a $7.4\sigma$ significance level. Combining our measurement with BOSS DR12 and Planck observations, we constrain the gravitational growth index to be $\gamma=0.580\pm0.082$, which is fully consistent with the prediction of general relativity. This paper is part of a set that analyses the eBOSS DR14 quasar sample.

Tomographic Analysis of Cosmic Structure Growth Using the eBOSS DR14 Quasar Dataset

The paper "The Clustering of the SDSS-IV Extended Baryon Oscillation Spectroscopic Survey DR14 Quasar Sample: A Tomographic Measurement of Cosmic Structure Growth and Expansion Rate Based on Optimal Redshift Weights" presents a comprehensive paper on the use of baryonic acoustic oscillations (BAO) and redshift-space distortions (RSD) to understand the cosmological expansion and growth of cosmic structures. The authors utilize the extended Baryon Oscillation Spectroscopic Survey (eBOSS) DR14 quasar sample, covering a redshift range of $0.8 < z < 2.2$, for this analysis.

Methodology

The authors have developed a novel methodology based on an optimal redshift weighting scheme to maximize the extraction of tomographic information from the BAO and RSD signals. This method allows for the utilization of the full potential of galaxy clustering information, providing a detailed mapping of the expansion history and structure growth of the universe. By applying this technique to the eBOSS DR14 quasar dataset, the paper enables a joint measurement of key cosmological parameters.

Key Results

1. Parameter Measurement: The authors report measurements of the growth rate $f\sigma_8$, BAO scale parameters such as $D_A$ and $H$, at four effective redshifts ($z_{\text{eff}} = 0.98, 1.23, 1.52, 1.94$). The paper finds these measurements to be consistent with the predictions of the ΛCDM model as tested against Planck data.
2. Support for Dark Energy: Combining their results with other datasets like BOSS DR12, MGS, and 6dFGS, the paper finds significant support for the presence of dark energy—more precisely, non-zero dark energy at a $7.4\sigma$ confidence level. This strengthens the observational evidence provided by independent cosmological probes.
3. Gravitational Growth Index: The paper provides constraints on the gravitational growth index $\gamma = 0.580 \pm 0.082$, aligning closely with the expectation from general relativity $\gamma = 0.545$. This indicates that the observed cosmic expansion and growth are consistent with the presence of dark energy as modeled in ΛCDM dynamics.

Implications

The findings of this paper carry significant weight in the continuing validation of the ΛCDM model. The results also highlight the efficacy of tomographic analysis methods and optimal redshift weighting in enhancing the precision of cosmological parameter measurements. This approach can effectively increase the diagnostic power of galaxy surveys, especially when extended over a wide redshift range.

Future Developments

The paper concludes by speculating on the future impact of the methodology on upcoming cosmic surveys planned by projects such as the Dark Energy Spectroscopic Instrument (DESI), Euclid, and others. These surveys will further refine our understanding of cosmic acceleration and the potential deviations from standard cosmological models, such as Einstein's theory of general relativity.

In essence, this paper exemplifies a robust quantitative leap toward capturing and interpreting the subtleties in cosmic structure formation and expansion dynamics with unprecedented accuracy through innovative techniques applied to large datasets like the eBOSS DR14. The results serve as a vital marker for future investigations into the fundamental drivers shaping our universe.