The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the correlation function of LOWZ and CMASS galaxies in Data Release 12

TL;DR

The paper reports precise baryon acoustic oscillation measurements from the DR12 BOSS data for the CMASS and LOWZ galaxy samples, achieving ~1%–2% distance precision at z=0.57 and z=0.32. By using isotropic and anisotropic BAO analyses with a de-wiggled template and reconstruction, and validating with two mock suites (QPM and MD-Patchy), the authors obtain robust distance constraints in a Planck-consistent ΛCDM framework. The results, including consensus combines of ξ(s) and P(k), demonstrate high-significance BAO detections and improved cosmological parameter constraints, notably on the expansion history and curvature. These measurements reinforce the BAO distance scale as a precise standard ruler and establish a solid baseline for future, higher-redshift BAO probes in upcoming surveys.

Abstract

We present distance scale measurements from the baryon acoustic oscillation signal in the CMASS and LOWZ samples from the Data Release 12 of the Baryon Oscillation Spectroscopic Survey (BOSS). The total volume probed is 14.5 Gpc$^3$, a 10 per cent increment from Data Release 11. From an analysis of the spherically averaged correlation function, we infer a distance to $z=0.57$ of $D_V(z)r^{\rm fid}_{\rm d}/r_ {\rm d}=2028\pm21$ Mpc and a distance to $z=0.32$ of $D_V(z)r^{\rm fid}_{\rm d}/r_{\rm d}=1264\pm22$ Mpc assuming a cosmology in which $r^{\rm fid}_{\rm d}=147.10$ Mpc. From the anisotropic analysis, we find an angular diameter distance to $z=0.57$ of $D_{\rm A}(z)r^{\rm fid}_{\rm d}/r_{\rm d}=1401\pm21$ Mpc and a distance to $z=0.32$ of $981\pm20$ Mpc, a 1.5 per cent and 2.0 per cent measurement respectively. The Hubble parameter at $z=0.57$ is $H(z)r_{\rm d}/r^{\rm fid}_{\rm d}=100.3\pm3.7$ km s$^{-1}$ Mpc$^{-1}$ and its value at $z=0.32$ is $79.2\pm5.6$ km s$^{-1}$ Mpc$^{-1}$, a 3.7 per cent and 7.1 per cent measurement respectively. These cosmic distance scale constraints are in excellent agreement with a $Λ$CDM model with cosmological parameters released by the recent Planck 2015 results.

Figures (10)

• Figure 1: Monopole (top) and quadrupole (bottom) of the CMASS and LOWZ correlation functions assuming our fiducial cosmology. Left panels show the CMASS correlation function, whereas right panels present the LOWZ correlation function. In all panels the dashed line indicates the correlation function pre-reconstruction. The lighter shade is the DR11 version for comparison. Error bars represent the square root of the diagonal elements of the covariance matrix.
• Figure 2: The correlation function of QPM mocks, pre-reconstruction (blue) and post-reconstruction (red). The upper panels show the average and standard deviation (dashed line and shaded regions) of the monopole of the CMASS (left) and LOWZ (right) correlation function of the QPM mocks. Bottom panels display the average and standard deviation of the quadrupole of the QPM correlation functions for CMASS (left) and LOWZ (right). A dotted line shows the clustering of the data for comparison.
• Figure 3: The correlation function of CMASS galaxies (left panels) and LOWZ galaxies (right panels). Top panels show the monopole of the correlation function post-reconstruction, bottom panels display the quadrupole of the correlation function. Error bars represent the square root of the diagonal elements of the covariance matrix. In all panels the best-fitting model is presented for reference (solid lines, see text for more details).
• Figure 4: Comparison of the pre- and post-reconstruction uncertainties in the anisotropic BAO fittings in QPM mocks. From left to right, we show how reconstruction generally improves $\sigma_{\alpha}$, $\sigma_{\alpha_{\perp}}$ and $\sigma_{\alpha_{\parallel}}$ respectively. The top row presents the results for LOWZ mocks and bottom row shows CMASS mocks. The uncertainties found in the Data Release 12 catalogues are shown with a red star.
• Figure 5: Statistics of BAO anisotropic fittings in LOWZ mocks. We present the distribution of measured values of $\alpha$ and $\epsilon$ in the mocks (top panels), as well as of their uncertainties $\sigma_{\alpha}$ and $\sigma_{\epsilon}$ (middle panels). Bottom panels show the distribution of the uncertainties in the line of sight distance scale and in the perpendicular direction $\sigma_{\alpha_{\parallel}}$ and $\sigma_{\alpha_{\perp}}$ respectively. Blue lines represent the pre-reconstruction BAO fittings, red lines display the post-reconstruction ones.