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Register a new userThe clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: BAO measurement from the LOS-dependent power spectrum of DR12 BOSS galaxies
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Publication date
2015
fields
Physics
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English
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[abridged] We present an anisotropic analysis of the baryonic acoustic oscillation (BAO) scale in the twelfth and final data release of the Baryonic Oscillation Spectroscopic Survey (BOSS). We independently analyse the LOWZ and CMASS galaxy samples: the LOWZ sample contains contains 361 762 galaxies with an effective redshift of $z_{rm LOWZ}=0.32$; the CMASS sample consists of 777 202 galaxies with an effective redshift of $z_{rm CMASS}=0.57$. We extract the BAO peak position from the monopole power spectrum moment, $alpha_0$, and from the $mu^2$ moment, $alpha_2$, where $mu$ is the cosine of the angle to the line-of-sight. The $mu^2$-moment provides equivalent information to that available in the quadrupole but is simpler to analyse. After applying a reconstruction algorithm to reduce the BAO suppression by bulk motions, we measure the BAO peak position in the monopole and $mu^2$-moment, which are related to radial and angular shifts in scale. We report $H(z_{rm LOWZ})r_s(z_d)=(11.60pm0.60)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm LOWZ})/r_s(z_d)=6.66pm0.16$ with a cross-correlation coefficient of $r_{HD_A}=0.41$, for the LOWZ sample; and $H(z_{rm CMASS})r_s(z_d)=(14.56pm0.37)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm CMASS})/r_s(z_d)=9.42pm0.13$ with a cross-correlation coefficient of $r_{HD_A}=0.47$, for the CMASS sample. We combine these results with the measurements of the BAO peak position in the monopole and quadrupole correlation function of the same dataset citep[][companion paper]{Cuestaetal2015} and report the consensus values: $H(z_{rm LOWZ})r_s(z_d)=(11.63pm0.69)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm LOWZ})/r_s(z_d)=6.67pm0.15$ with $r_{HD_A}=0.35$ for the LOWZ sample; $H(z_{rm CMASS})r_s(z_d)=(14.67pm0.42)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm CMASS})/r_s(z_d)=9.47pm0.12$ with $r_{HD_A}=0.52$ for the CMASS sample.
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We measure and analyse the clustering of the Baryon Oscillation Spectroscopic Survey (BOSS) relative to the line-of-sight (LOS), for LOWZ and CMASS galaxy samples drawn from the final Data Release 12 (DR12). The LOWZ sample contains 361,762 galaxies with an effective redshift of $z_{rm lowz}=0.32$, and the CMASS sample 777,202 galaxies with an effective redshift of $z_{rm cmass}=0.57$. From the power spectrum monopole and quadrupole moments around the LOS, we measure the growth of structure parameter $f$ times the amplitude of dark matter density fluctuations $sigma_8$ by modeling the Redshift-Space Distortion signal. When the geometrical Alcock-Paczynski effect is also constrained from the same data, we find joint constraints on $fsigma_8$, the product of the Hubble constant and the comoving sound horizon at the baryon drag epoch $H(z)r_s(z_d)$, and the angular distance parameter divided by the sound horizon $D_A(z)/r_s(z_d)$. We find $f(z_{rm lowz})sigma_8(z_{rm lowz})=0.394pm0.062$, $D_A(z_{rm lowz})/r_s(z_d)=6.35pm0.19$, $H(z_{rm lowz})r_s(z_d)=(11.41pm 0.56),{10^3rm km}s^{-1}$ for the LOWZ sample, and $f(z_{rm cmass})sigma_8(z_{rm cmass})=0.444pm0.038$, $D_A(z_{rm cmass})/r_s(z_d)=9.42pm0.15$, $H(z_{rm cmass})r_s(z_d)=(13.92 pm 0.44), {10^3rm km}s^{-1}$ for the CMASS sample. We find general agreement with previous BOSS DR11 measurements. Assuming the Hubble parameter and angular distance parameter are fixed at fiducial $Lambda$CDM values, we find $f(z_{rm lowz})sigma_8(z_{rm lowz})=0.485pm0.044$ and $f(z_{rm cmass})sigma_8(z_{rm cmass})=0.436pm0.022$ for the LOWZ and CMASS samples, respectively.
We perform a tomographic baryon acoustic oscillations (BAO) analysis using the monopole, quadrupole and hexadecapole of the redshift-space galaxy power spectrum measured from the pre-reconstructed combined galaxy sample of the completed Sloan Digital Sky Survey (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS) Data Release (DR)12 covering the redshift range of $0.20<z<0.75$. By allowing for overlap between neighbouring redshift slices, we successfully obtained the isotropic and anisotropic BAO distance measurements within nine redshift slices to a precision of $1.5%-3.4%$ for $D_V/r_d$, $1.8% -4.2%$ for $D_A/r_d$ and $3.7% - 7.5%$ for $H r_d$, depending on effective redshifts. We provide our BAO measurement of $D_A/r_d$ and $H r_d$ with the full covariance matrix, which can be used for cosmological implications. Our measurements are consistent with those presented in citet{Acacia}, in which the BAO distances are measured at three effective redshifts. We constrain dark energy parameters using our measurements, and find an improvement of the Figure-of-Merit of dark energy in general due to the temporal BAO information resolved. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS.
We perform a tomographic baryon acoustic oscillations analysis using the two-point galaxy correlation function measured from the combined sample of BOSS DR12, which covers the redshift range of $0.2<z<0.75$. Splitting the sample into multiple overlapping redshift slices to extract the redshift information of galaxy clustering, we obtain a measurement of $D_A(z)/r_d$ and $H(z)r_d$ at nine effective redshifts with the full covariance matrix calibrated using MultiDark-Patchy mock catalogues. Using the reconstructed galaxy catalogues, we obtain the precision of $1.3%-2.2%$ for $D_A(z)/r_d$ and $2.1%-6.0%$ for $H(z)r_d$. To quantify the gain from the tomographic information, we compare the constraints on the cosmological parameters using our 9-bin BAO measurements, the consensus 3-bin BAO and RSD measurements at three effective redshifts in citet{Alam2016}, and the non-tomographic (1-bin) BAO measurement at a single effective redshift. Comparing the 9-bin with 1-bin constraint result, it can improve the dark energy Figure of Merit by a factor of 1.24 for the Chevallier-Polarski-Linder parametrisation for equation of state parameter $w_{rm DE}$. The errors of $w_0$ and $w_a$ from 9-bin constraints are slightly improved when compared to the 3-bin constraint result.
We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises 1.2 million massive galaxies over an effective area of 9329 deg^2 and volume of 18.7 Gpc^3, divided into three partially overlapping redshift slices centred at effective redshifts 0.38, 0.51, and 0.61. We measure the angular diameter distance DM and Hubble parameter H from the baryon acoustic oscillation (BAO) method after applying reconstruction to reduce non-linear effects on the BAO feature. Using the anisotropic clustering of the pre-reconstruction density field, we measure the product DM*H from the Alcock-Paczynski (AP) effect and the growth of structure, quantified by f{sigma}8(z), from redshift-space distortions (RSD). We combine measurements presented in seven companion papers into a set of consensus values and likelihoods, obtaining constraints that are tighter and more robust than those from any one method. Combined with Planck 2015 cosmic microwave background measurements, our distance scale measurements simultaneously imply curvature {Omega}_K =0.0003+/-0.0026 and a dark energy equation of state parameter w = -1.01+/-0.06, in strong affirmation of the spatially flat cold dark matter model with a cosmological constant ({Lambda}CDM). Our RSD measurements of f{sigma}_8, at 6 per cent precision, are similarly consistent with this model. When combined with supernova Ia data, we find H0 = 67.3+/-1.0 km/s/Mpc even for our most general dark energy model, in tension with some direct measurements. Adding extra relativistic species as a degree of freedom loosens the constraint only slightly, to H0 = 67.8+/-1.2 km/s/Mpc. Assuming flat {Lambda}CDM we find {Omega}_m = 0.310+/-0.005 and H0 = 67.6+/-0.5 km/s/Mpc, and we find a 95% upper limit of 0.16 eV/c^2 on the neutrino mass sum.
We analyse the broad-range shape of the monopole and quadrupole correlation functions of the BOSS Data Release 12 (DR12) CMASS and LOWZ galaxy sample to obtain constraints on the Hubble expansion rate $H(z)$, the angular-diameter distance $D_A(z)$, the normalised growth rate $f(z)sigma_8(z)$, and the physical matter density $Omega_mh^2$. We adopt wide and flat priors on all model parameters in order to ensure the results are those of a `single-probe galaxy clustering analysis. We also marginalise over three nuisance terms that account for potential observational systematics affecting the measured monopole. However, such Monte Carlo Markov Chain analysis is computationally expensive for advanced theoretical models, thus we develop a new methodology to speed up our analysis. We obtain ${D_A(z)r_{s,fid}/r_s$Mpc, $H(z)r_s/r_{s,fid}$kms$^{-1}$Mpc$^{-1}$, $f(z)sigma_8(z)$, $Omega_m h^2}$ = ${956pm28$ , $75.0pm4.0$ , $0.397 pm 0.073$, $0.143pm0.017}$ at $z=0.32$ and ${1421pm23$, $96.7pm2.7$ , $0.497 pm 0.058$, $0.137pm0.015}$ at $z=0.59$ where $r_s$ is the comoving sound horizon at the drag epoch and $r_{s,fid}=147.66$Mpc for the fiducial cosmology in this study. In addition, we divide the galaxy sample into four redshift bins to increase the sensitivity of redshift evolution. However, we do not find improvements in terms of constraining dark energy model parameters. Combining our measurements with Planck data, we obtain $Omega_m=0.306pm0.009$, $H_0=67.9pm0.7$kms$^{-1}$Mpc$^{-1}$, and $sigma_8=0.815pm0.009$ assuming $Lambda$CDM; $Omega_k=0.000pm0.003$ assuming oCDM; $w=-1.01pm0.06$ assuming $w$CDM; and $w_0=-0.95pm0.22$ and $w_a=-0.22pm0.63$ assuming $w_0w_a$CDM. Our results show no tension with the flat $Lambda$CDM cosmological paradigm. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS.
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