The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Measuring D_A and H at z=0.57 from the Baryon Acoustic Peak in the Data Release 9 Spectroscopic Galaxy Sample

Abstract

We present measurements of the angular diameter distance to and Hubble parameter at z=0.57 from the measurement of the baryon acoustic peak in the correlation of galaxies from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey. Our analysis is based on a sample from Data Release 9 of 264,283 galaxies over 3275 square degrees in the redshift range 0.43<z<0.70. We use two different methods to provide robust measurement of the acoustic peak position across and along the line of sight in order to measure the cosmological distance scale. We find D_A(0.57) = 1408 +/- 45 Mpc and H(0.57) = 92.9 +/- 7.8 km/s/Mpc for our fiducial value of the sound horizon. These results from the anisotropic fitting are fully consistent with the analysis of the spherically averaged acoustic peak position presented in Anderson et al, 2012. Our distance measurements are a close match to the predictions of the standard cosmological model featuring a cosmological constant and zero spatial curvature.

Figures (15)

• Figure 1: Average of mocks (crosses) with our model of the correlation function (solid line) overplotted. The upper panels show the monopole (left) and quadrupole (right) while the lower panels plot the transverse (left) and radial (right) wedges. No fit to the shape was done here, but the models were normalized to match the observed signals.
• Figure 2: Average of mocks before (grey) and after (black) reconstruction. We see a sharpening of the acoustic feature in the monopole, and a drastic decrease in amplitude of the quadrupole on large scales, which is consistent with the fact that reconstruction removes large-scale redshift-space distortions. The correlation function of both angular wedges show a clear sharpening of the acoustic feature, a reduction of amplitude on large-scales in the transverse wedge and a corresponding increase in the amplitude in the radial wedge.
• Figure 3: A comparison of $\alpha_{\perp}$ and $\alpha_{\parallel}$ for the 600 mock catalogues before and after reconstruction. These values have been derived from the multipole analysis. The points mostly lie on the 1:1 line, but the number of outliers are reduced after reconstruction.
• Figure 4: The distribution of $\alpha_\perp$ versus $\alpha_\parallel$ from the 600 mock catalogues after reconstruction. As in Fig. \ref{['fig:reccomp']}, these values are derived from the multipole analysis. The estimates of the two distances are anti-correlated, with a correlation coefficient of $\sim -0.44$. Note that $H \sim 1/\alpha_{||}$.
• Figure 5: The errors in estimated distances, $\sigma_{\alpha_\perp}/\alpha_\perp$ versus $\sigma_{\alpha_\parallel}/\alpha_\parallel$, for the mock catalogues. The line of sight distance is more weakly constrained than the transverse distance.