The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: structure growth rate measurement from the anisotropic quasar power spectrum in the redshift range $0.8<z<2.2$

TL;DR

This work conducts a full-shape redshift-space distortion analysis of the SDSS-IV eBOSS DR14Q quasar sample to extract cosmological information in the redshift range $0.8<z<2.2$. Using power spectrum multipoles up to the hexadecapole and a TNS-based model with 2-loop resumed PT, the authors constrain $f\sigma_8$, $D_A/r_s$, and $H r_s$ at $z_{\rm eff}=1.52$, with a comprehensive assessment of observational and modeling systematics via mock catalogs. The results are in good agreement with Planck $\Lambda$CDM and with companion DR14Q analyses, and show consistent constraints when combining RSD with BAO information. The paper also explores redshift evolution by splitting into three overlapping redshift bins and demonstrates the robustness of the cosmological inferences to analysis choices. These findings validate quasars as a viable tracer for precision cosmology in the $z\sim1-2$ regime and inform future DESI/Euclid-like surveys.

Abstract

We analyse the clustering of the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 14 quasar sample (DR14Q). We measure the redshift space distortions using the power spectrum monopole, quadrupole and hexadecapole inferred from 148,659 quasars between redshifts 0.8 and 2.2 covering a total sky footprint of 2112.9 deg$^2$. We constrain the logarithmic growth of structure times the amplitude of dark matter density fluctuations, $fσ_8$, and the Alcock-Paczynski dilation scales which allow constraints to be placed on the angular diameter distance $D_A(z)$ and the Hubble $H(z)$ parameter. At the effective redshift of $z_{\rm eff}=1.52$, $fσ_8(z_{\rm eff})=0.420\pm0.076$, $H(z_{\rm eff})=[162\pm 12]\, (r_s^{\rm fid}/r_s)\,{\rm km\, s}^{-1}{\rm Mpc}^{-1}$, and $D_A(z_{\rm eff})=[1.85\pm 0.11]\times10^3\,(r_s/r_s^{\rm fid})\,{\rm Mpc}$, where $r_s$ is the comoving sound horizon at the baryon drag epoch and the superscript `fid' stands for its fiducial value. The errors take into account the full error budget, including systematics and statistical contributions. These results are in full agreement with the current $Λ$-Cold Dark Matter ($Λ$CDM) cosmological model inferred from Planck measurements. Finally, we compare our measurements with other eBOSS companion papers and find excellent agreement, demonstrating the consistency and complementarity of the different methods used for analysing the data.

Figures (26)

• Figure 1: Redshift success rate as a function of plate position for the DR14Q catalogue after and before visual inspections, top and bottom panels, respectively. The higher failure rate (lower success rate) in the edges of the plate across the $x$-axis is caused by the less sensitive areas of the detector associated to those plate regions. The higher failure rate in the SGC plates is associated to a poorer photometrie conditions in the SGC compared to those in the NGC. For each tile of the survey, the $x$-axis of the plate is aligned along the iso-declination lines, and the $y$-axis along the iso-right ascension lines, in such a way that the top areas of the plate in the figure correspond to objects with higher declination than the lower areas of the plate.
• Figure 2: Mean density of 148,659 quasars in the DR14Q catalogue as a function of redshift, for the NGC and SGC regions in blue and yellow lines, respectively. The slight difference between the two regions is caused by differences in the target efficiency.
• Figure 3: Angular footprint of the DR14Q sample for the NGC (top panels) and SGC (bottom panels), where the colour mapping indicates the completeness, $C_{\rm eBOSS}$ (see Eq. \ref{['eq:completeness']}), and the imaging weight, $w_{\rm sys}$, (see Eq. \ref{['eq:wsys']}), in the left and right panels, respectively.
• Figure 4: OuterRim N-body simulation power spectrum monopole (solid lines) and quadrupole (dashed) lines, computed as the mean of 20 realisations. The colours represent different satellite fractions used, no-sat with $f=0$ (orange lines), std with $f=0.13$ (dark-blue lines), and high with $f=0.22$ (red lines), with no smearing. The light blue lines correspond to the smearing case for the $f_{\rm std}$ satellite fraction. At large scales increasing the satellite fraction increases the amplitude of the monopole, consistent with an enhancement of the linear bias parameter. At small scales the satellites induce a non-linear damping term consistent with the expected by a intra-halo velocity dispersion. This effect is saturated when the redshift smearing effect is included, making it difficult to distinguish among the cases with different fractions at small scales (not plotted for clarity).
• Figure 5: Top panel: The DR14 quasar power spectrum monopole (green), quadrupole (orange) and hexadecapole (purple) in the redshift range $0.8\leq z\leq2.2$, including both NGC and SGC sky patches. The displayed error-bars are the rms of 1000 realisations of the ez-mocks. The dashed black lines represent the best-fitting model for the $k$-range $0.02\leq k\,[h{\rm Mpc}^{-1}]\leq0.30$. The bottom sub-panel show the differences between the model and data, divided by the diagonal errors, using the same colour scheme. The 2 and $3\sigma$ confidence levels are marked with dashed and dotted black lines, respectively. Bottom panel: Monopole and quadrupole measurement of the data for the different redshift estimates described in § \ref{['sec:redshifts']}: $z_{\rm fid}$ in black symbols, $z_{\rm Mg II}$ in red symbols, and $z_{\rm PCA}$ in blue symbols. The bottom sub-panels display the difference with respect to the fiducial redshift estimate relative to the statistical errors for the monopole and quadrupole. For clarity we do not display the results for the hexadecapole, where the degree of agreement is similar to the other two multipoles.