We study the clustering of luminous red galaxies in the latest spectroscopic Sloan Digital Sky Survey data releases (DR), DR6 and DR7, which sample over 1 Gpc3 h−3 to z= 0.47. The two‐point correlation function ξ(σ, π) is estimated as a function of perpendicular σ and line‐of‐sight π (radial) directions. We find significant detection of a peak at r≃ 110 Mpc h−1, which shows as a circular ring in the σ–π plane. There is also significant evidence of a peak along the radial direction whose shape is consistent with its origination from the recombination‐epoch baryon acoustic oscillations (BAO). A ξ(σ, π) model with no radial BAO peak is disfavoured at 3.2σ, whereas a model with no magnification bias is disfavoured at 2σ. The radial data enable, for the first time, a direct measurement of the Hubble parameter H(z) as a function of redshift. This is independent of earlier BAO measurements which used the spherically averaged (monopole) correlation to constrain an integral of H(z). Using the BAO peak position as a standard ruler in the radial direction, we find H(z= 0.24) = 79.69 ± 2.32 (±1.29) km s−1 Mpc−1 for z= 0.15–0.30 and H(z= 0.43) = 86.45 ± 3.27 (±1.69) km s−1 Mpc−1 for z= 0.40–0.47. The first error is a model‐independent statistical estimation and the second accounts for systematics both in the measurements and in the model. For the full sample, z= 0.15–0.47, we find H(z= 0.34) = 83.80 ± 2.96 (±1.59) km s−1 Mpc−1.

Abstract. We analyse simulations of the Pacific Ocean oxygen minimum zones (OMZs) from 11 Earth system model contributions to the Coupled Model Intercomparison Project Phase 5, focusing on the mean state and climate change projections. The simulations tend to overestimate the volume of the OMZs, especially in the tropics and Southern Hemisphere. Compared to observations, five models introduce incorrect meridional asymmetries in the distribution of oxygen including larger southern OMZ and weaker northern OMZ, due to interhemispheric biases in intermediate water mass ventilation. Seven models show too deep an extent of the tropical hypoxia compared to observations, stemming from a deficient equatorial ventilation in the upper ocean, combined with too large a biologically driven downward flux of particulate organic carbon at depth, caused by particle export from the euphotic layer that is too high and remineralization in the upper ocean that is too weak. At interannual timescales, the dynamics of oxygen in the eastern tropical Pacific OMZ is dominated by biological consumption and linked to natural variability in the Walker circulation. However, under the climate change scenario RCP8.5, all simulations yield small and discrepant changes in oxygen concentration at mid depths in the tropical Pacific by the end of the 21st century due to an almost perfect compensation between warming-related decrease in oxygen saturation and decrease in biological oxygen utilization. Climate change projections are at odds with recent observations that show decreasing oxygen levels at mid depths in the tropical Pacific. Out of the OMZs, all the CMIP5 models predict a decrease of oxygen over most of the surface and deep ocean at low latitudes and over all depths at high latitudes due to an overall slow-down of ventilation and increased temperature.

This is the first paper of a series where we study the clustering of LRG galaxies in the latest spectroscopic Sloan Digital Sky Survey (SDSS) data release, DR6, which has 75 000 LRG galaxies covering over 1 Gpc3 h−3 at 0.15 < z < 0.47. Here we focus on modelling redshift‐space distortions in ξ(π, σ), the two‐point correlation function in separate line of sight and perpendicular directions, on large scales. We use large mock simulations to study the validity of models and errors. We show that errors in the data are dominated by a shot‐noise term that is 40 per cent larger than the Poisson error commonly used. We first use the normalized quadrupole for the whole sample (mean z= 0.34) to estimate β=f(Ωm)/b= 0.34 ± 0.03, where f(Ωm) is the linear velocity growth factor and b is the linear bias parameter that relates galaxy to matter fluctuations on large scales. We next use the full ξ(π, σ) plane to find Ω0m= 0.245 ± 0.020 (h= 0.72) and the biased amplitude bσ8= 1.56 ± 0.09. For standard gravity, we can combine these measurements to break degeneracies and find σ8= 0.85 ± 0.06, b= 1.85 ± 0.25 and f(Ωm) = 0.64 ± 0.09. We present constraints for modified theories of gravity and find that standard gravity is consistent with data as long as 0.80 < σ8 < 0.92. We also calculate the cross‐correlation with WMAP5 and show how both methods to measure the growth history are complementary to constrain non‐standard models of gravity. Finally, we show results for different redshift slices, including a prominent BAO peak in the monopole at different redshifts. The ξ(π, σ) data on large scales is shown to be in remarkable agreement with predictions and shows a characteristic large region of negative correlation in the line of sight, a BAO ring and a prominent radial BAO peak. The significance of this is presented in Paper IV of this series. We include a study of possible systematic effects in our analysis to find that these results are quite robust.

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Cosmological galaxy surveys aim at mapping the largest volumes to test models with techniques such as cluster abundance, cosmic shear correlations or baryon acoustic oscillations (BAO), which are designed to be independent of galaxy bias. Here, we explore an alternative route to constrain cosmology: sampling more moderate volumes with the cross‐correlation of photometric and spectroscopic surveys. We consider the angular galaxy–galaxy auto‐correlation in narrow redshift bins and its combination with different probes of weak gravitational lensing (WL) and redshift space distortions (RSD). Including the cross‐correlation of these surveys improves by factors of a few the constraints on both the dark energy equation of state w(z) and the cosmic growth history, parametrized by γ. The additional information comes from using many narrow redshift bins and from measurement of galaxy bias with both WL and RSD, breaking degeneracies that are present when using each method separately. We show forecasts for a joint w(z) and γ figure of merit (FoM) using linear scales over a deep (iAB < 24) photometric survey and a brighter (iAB < 22.5) spectroscopic or very accurate (0.3 per cent) photometric redshift survey. Magnification or shear in the photometric sample produce FoM that are of the same order of magnitude of those of RSD or BAO over the spectroscopic sample. However, the cross‐correlation of these probes over the same area yields a FoM that is up to a factor of 100 times larger. Magnification alone, without shape measurements, can also be used for these cross‐correlations and can produce better results than using shear alone. For a spectroscopic follow‐up survey strategy, measuring the spectra of the foreground lenses to perform this cross‐correlation provides five times better FoM than targeting the higher redshift tail of the galaxy distribution to study BAO over a 2.5 times larger volume.