An Empirical Analysis of Baryon Acoustic Oscillations in Galaxy and Quasar Clustering

We present our analysis of the baryon acoustic oscillation (BAO) signal in the correlation functions of LOWZ and CMASS galaxy samples from Data Release 12 of the SDSS BOSS survey. We draw a comparison between our results and the findings of Cuesta et al. (2016) who analysed the BAO feature in the same datasets. Upon using subsets of the data to obtain an empirical estimate of the uncertainties on the correlation functions, we find our results to be in general agreement with the uncertainties presented by Cuesta et al. (2016), obtained from simulated mocks. We detect the BAO peak at ~4 sigma and ~7 sigma in the correlation function of the LOWZ and CMASS samples respectively. We demonstrate that when fitting the correlation functions with our fiducial LCDM model, the A(s) nuisance fitting parameters play a significant role in providing a good fit. Based on a F-ratio test, we find that in our primary fitting range, the simple LCDM model without the nuisance fitting terms is rejected in favour of the full model as indicated by the small p-values of p = 0.018 and p = 0.00084, for the CMASS and LOWZ samples respectively. We demonstrate that the significance of the detection of the BAO peak is the quantity most sensitive to the choice of the fitting range. Based on isotropic fitting to the correlation functions, we obtain a distance of DV(z=0.32)rd,fid/rd=1226±32 Mpc and DV(z=0.57)rd,fid/rd=1988±24 Mpc, a 2.6 per cent and 1.2 percent measurement respectively, assuming a fiducial sound horizon rd,fid=147.10 Mpc. We extend our BAO analysis to higher redshifts by performing fitting to the mean of the correlation functions obtained by Chehade et al. (2016) for the 2QDESp, SDSS DR5 UNIFORM, 2QZ and 2SLAQ quasar samples. This gives a distance constraint of DV(z=1.49)rd,fid/rd=3583±249 Mpc (assuming rd,fid=147.70 Mpc), a 6.9 per cent measurement to z=1.49, the mean redshift of the combined QSO sample.