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We analyse the full shape of anisotropic clustering measurements from the extended Baryon Oscillation Spectroscopic Survey quasar sample together with the combined galaxy sample from the Baryon Oscillation Spectroscopic Survey. We obtain constraints on the cosmological parameters independent of the Hubble parameter h for the extensions of the Lambda cold dark matter (ΛCDM) models, focusing on cosmologies with free dark energy equation of state parameter w. We combine the clustering constraints with those from the latest cosmic microwave background data from Planck to obtain joint constraints for these cosmologies for w and the additional extension parameters – its time evolution w a, the physical curvature density ω K and the neutrino mass sum ∑ m ν. Our joint constraints are consistent with a flat ΛCDM cosmological model within 68  per cent confidence limits. We demonstrate that the Planck data are able to place tight constraints on the clustering amplitude today, σ12, in cosmologies with varying w and present the first constraints for the clustering amplitude for such cosmologies, which is found to be slightly higher than the ΛCDM value. Additionally, we show that when we vary w and allow for non-flat cosmologies and the physical curvature density is used, Planck prefers a curved universe at 4σ significance, which is ∼2σ higher than when using the relative curvature density ΩK. Finally, when w is varied freely, clustering provides only a modest improvement (of 0.021 eV) on the upper limit of ∑ m ν. [ABSTRACT FROM AUTHOR]

We present a new approach to describe statistics of the non-linear matter density field that exploits a degeneracy in the impact of different cosmological parameters on the linear dimensionless matter power spectrum, |$\Delta ^2_{\rm L}(k)$|⁠. We classify all cosmological parameters into two groups, shape parameters, which determine the shape of |$\Delta ^2_{\rm L}(k)$|⁠ , and evolution parameters, which only affect its amplitude at any given redshift. With this definition, the time evolution of |$\Delta ^2_{\rm L}(k)$| in models with identical shape parameters but different evolution parameters can be mapped from one to the other by relabelling the redshifts that correspond to the same clustering amplitude, which we characterize by the linear mass fluctuation in spheres of radius |$12\, {\rm Mpc}$|⁠ , σ12(z). We use N -body simulations to show that the same evolution-mapping relation gives a good description of the non-linear power spectrum, the halo mass function, or the full density field. The deviations from the exact degeneracy are the result of the different structure formation histories experienced by each model to reach the same clustering amplitude and can be accurately described in terms of differences in the suppression factor g (a) = D (a)/ a. These relations can be used to drastically reduce the number of parameters required to describe the cosmology dependence of the power spectrum. We show how this can help to speed up the inference of parameter constraints from cosmological observations. We also present a new design of an emulator of the non-linear power spectrum whose predictions can be adapted to an arbitrary choice of evolution parameters and redshift. [ABSTRACT FROM AUTHOR]

We present the analysis of the full shape of anisotropic clustering measurement from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) quasar sample together with the combined galaxy sample from the Baryon Oscillation Spectroscopic Survey (BOSS), re-analysed using an updated recipe for the non-linear matter power spectrum and the non-local bias parameters. We obtain constraints for flat Lambda cold dark matter cosmologies, focusing on the cosmological parameters that are independent of the Hubble parameter h. Our recovered value for the Root Mean Square (RMS) linear perturbation theory variance as measured on the scale of |$12\, {\rm Mpc}$| is σ12 = 0.805 ± 0.049, while using the traditional reference scale of |$8\, h^{-1}\, {\rm Mpc}$| gives σ8 = 0.815 ± 0.044. We quantify the agreement between our measurements and the latest cosmic microwave background data from Planck using the suspiciousness metric, and find them to be consistent within 0.64 ± 0.03σ. Combining our clustering constraints with the 3 × 2pt data sample from the Dark Energy Survey Year 1 release slightly degrades this agreement to the level of 1.54 ± 0.08σ, while still showing an overall consistency with Planck. We furthermore study the effect of imposing a Planck – like prior on the parameters that define the shape of the linear matter power spectrum, and find significantly tighter constraints on the parameters that control the evolution of density fluctuations. In particular, the combination of low-redshift data sets prefers a value of the physical dark energy density ωDE = 0.335 ± 0.011, which is 1.7σ higher than the one preferred by Planck. [ABSTRACT FROM AUTHOR]

Minkowski functionals (MFs) are a set of statistics that characterize the geometry and topology of the cosmic density field and contain complementary information to the standard two-point analyses. We present medusa , an implementation of an accurate method for estimating the MFs of three-dimensional point distributions. These estimates are inferred from triangulated isodensity surfaces that are constructed from the Delaunay tessellation of the input point sample. medusa can account for periodic boundary conditions, which is crucial for the analysis of N -body simulations. We validate our code against several test samples with known MFs, including Gaussian random fields with a ΛCDM power spectrum, and find excellent agreement with the theory predictions. We use medusa to measure the MFs of synthetic galaxy catalogues constructed from N -body simulations. Our results show clearly non-Gaussian signatures that arise from the non-linear gravitational evolution of the density field. We find that, although redshift-space distortions change our MFs estimates, their impact is considerably reduced if these measurements are expressed as a function of the volume-filling fraction. We also show that the effect of Alcock–Paczynski (AP) distortions on the MFs can be described by scaling them with different powers of the isotropic AP parameter q defined in terms of the volume-averaged distance D V(z). Thus the MFs estimates by medusa are useful probes of non-linearities in the density field, and the expansion and growth of structure histories of the Universe. [ABSTRACT FROM AUTHOR]

The construction of catalogues of a particular type of galaxy can be complicated by interlopers contaminating the sample. In spectroscopic galaxy surveys this can be due to the misclassification of an emission line; for example in the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) low-redshift [O  ii ] emitters may make up a few per cent of the observed Ly  α emitter (LAE) sample. The presence of contaminants affects the measured correlation functions and power spectra. Previous attempts to deal with this using the cross-correlation function have assumed sources at a fixed redshift, or not modelled evolution within the adopted redshift bins. However, in spectroscopic surveys like HETDEX, where the contamination fraction is likely to be redshift dependent, the observed clustering of misclassified sources will appear to evolve strongly due to projection effects, even if their true clustering does not. We present a practical method for accounting for the presence of contaminants with redshift-dependent contamination fractions and projected clustering. We show using mock catalogues that our method, unlike existing approaches, yields unbiased clustering measurements from the upcoming HETDEX survey in scenarios with redshift-dependent contamination fractions within the redshift bins used. We show our method returns autocorrelation functions with systematic biases much smaller than the statistical noise for samples with at least as high as 7 per cent contamination. We also present and test a method for fitting for the redshift-dependent interloper fraction using the LAE–[O  ii ] galaxy cross-correlation function, which gives less biased results than assuming a single interloper fraction for the whole sample. [ABSTRACT FROM AUTHOR]

All estimators of the two-point correlation function are based on a random catalogue, a set of points with no intrinsic clustering following the selection function of a survey. High-accuracy estimates require the use of large random catalogues, which imply a high computational cost. We propose to replace the standard random catalogues by glass-like point distributions or glass catalogues whose power spectrum P (k) ∝ k 4 exhibits significantly less power on scales larger than the mean interparticle separation than a Poisson distribution with the same number of points. We show that these distributions can be obtained by iteratively applying the technique of Zeldovich reconstruction commonly used in studies of baryon acoustic oscillations (BAO). We provide a modified version of the widely used Landy–Szalay estimator of the correlation function adapted to the use of glass catalogues and compare its performance with the results obtained using random samples. Our results show that glass-like samples do not add any bias with respect to the results obtained using Poisson distributions. On scales larger than the mean interparticle separation of the glass catalogues, the modified estimator leads to a significant reduction of the variance of the Legendre multipoles ξℓ(s) with respect to the standard Landy–Szalay results with the same number of points. The size of the glass catalogue required to achieve a given accuracy in the correlation function is significantly smaller than when using random samples. Their use could help us to drastically reduce the computational cost of configuration-space clustering analysis of future surveys while maintaining high-accuracy requirements. [ABSTRACT FROM AUTHOR]

We measure the anisotropic clustering of the quasar sample from Data Release 16 (DR16) of the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey (eBOSS). A sample of 343 708 spectroscopically confirmed quasars between redshift 0.8 < z < 2.2 are used as tracers of the underlying dark matter field. In comparison with DR14 sample, the final sample doubles the number of objects as well as the survey area. In this paper, we present the analysis in configuration space by measuring the two-point correlation function and decomposing it using the Legendre polynomials. For the full-shape analysis of the Legendre multipole moments, we measure the baryon acoustic oscillation (BAO) distance and the growth rate of the cosmic structure. At an effective redshift of z eff = 1.48, we measure the comoving angular diameter distance D M(z eff)/ r drag = 30.66 ± 0.88, the Hubble distance D H(z eff)/ r drag = 13.11 ± 0.52, and the product of the linear growth rate and the rms linear mass fluctuation on scales of |$8 \, h^{-1}\, {\rm Mpc}$|⁠ , f σ8(z eff) = 0.439 ± 0.048. The accuracy of these measurements is confirmed using an extensive set of mock simulations developed for the quasar sample. The uncertainties on the distance and growth rate measurements have been reduced substantially (∼45 and ∼30 per cent) with respect to the DR14 results. We also perform a BAO-only analysis to cross check the robustness of the methodology of the full-shape analysis. Combining our analysis with the Fourier-space analysis, we arrive at |$D^{{\bf c}}_{\rm M}(z_{\rm eff})/r_{\rm drag} = 30.21 \pm 0.79$|⁠ , |$D^{{\bf c}}_{\rm H}(z_{\rm eff})/r_{\rm drag} = 13.23 \pm 0.47$|⁠ , and |$f\sigma _8^{{\bf c}}(z_{\rm eff}) = 0.462 \pm 0.045$|⁠. [ABSTRACT FROM AUTHOR]

This paper is the first in a set that analyses the covariance matrices of clustering statistics obtained from several approximate methods for gravitational structure formation. We focus here on the covariance matrices of anisotropic two-point correlation function measurements. Our comparison includes seven approximate methods, which can be divided into three categories: predictive methods that follow the evolution of the linear density field deterministically (ice-cola, peak patch, and pinocchio), methods that require a calibration with N -body simulations (patchy and halogen), and simpler recipes based on assumptions regarding the shape of the probability distribution function (PDF) of density fluctuations (lognormal and Gaussian density fields). We analyse the impact of using covariance estimates obtained from these approximate methods on cosmological analyses of galaxy clustering measurements, using as a reference the covariances inferred from a set of full N -body simulations. We find that all approximate methods can accurately recover the mean parameter values inferred using the N -body covariances. The obtained parameter uncertainties typically agree with the corresponding N -body results within 5 per cent for our lower mass threshold and 10 per cent for our higher mass threshold. Furthermore, we find that the constraints for some methods can differ by up to 20 per cent depending on whether the halo samples used to define the covariance matrices are defined by matching the mass, number density, or clustering amplitude of the parent N -body samples. The results of our configuration-space analysis indicate that most approximate methods provide similar results, with no single method clearly outperforming the others. [ABSTRACT FROM AUTHOR]

We explore the cosmological implications of anisotropic clustering measurements of the quasar sample from Data Release 14 (DR14) of the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey (eBOSS) in configuration space. The $${\sim } 147\, 000$$ quasar sample observed by eBOSS offers a direct tracer of the density field and bridges the gap of previous baryon acoustic oscillation measurements between redshift 0.8 < $$z$$ < 2.2. By analysing the two-point correlation function characterized by clustering wedges $$\xi _{\rm w_i}(s)$$ and multipoles ξℓ(s), we measure the angular diameter distance, Hubble parameter, and cosmic structure growth rate. We define a systematic error budget for our measurements based on the analysis of N -body simulations and mock catalogues. Based on the DR14 large-scale structure quasar sample at the effective redshift $$z$$ eff = 1.52, we find the growth rate of cosmic structure f σ8($$z$$ eff) = 0.396 ± 0.079, and the geometric parameters D V($$z$$)/ r d = 26.47 ± 1.23, and F AP($$z$$) = 2.53 ± 0.22, where the uncertainties include both statistical and systematic errors. These values are in excellent agreement with the best-fitting standard Λ cold dark matter model to the latest cosmic microwave background data from Planck. [ABSTRACT FROM AUTHOR]

We investigate the cosmological implications of studying galaxy clustering using a tomographic approach applied to the final Baryon Oscillation Spectroscopic Survey (BOSS) DR12 galaxy sample, including both auto- and cross-correlation functions between redshift shells. We model the signal of the full shape of the angular correlation function, ω(θ), in redshift bins using state-of-the-art modelling of non-linearities, bias and redshift-space distortions. We present results on the redshift evolution of the linear bias of BOSS galaxies, which cannot be obtained with traditional methods for galaxy-clustering analysis. We also obtain constraints on cosmological parameters, combining this tomographic analysis with measurements of the cosmic microwave background (CMB) and Type Ia supernova (SNIa).We explore a number of cosmological models, including the standard Λ cold darkmattermodel and its most interesting extensions, such as deviations from wDE=-1, non-minimal neutrino masses, spatial curvature and deviations from general relativity (GR) using the growth-index γ parametrization. These results are, in general, comparable to the most precise present-day constraints on cosmological parameters, and show very good agreement with the standard model. In particular, combining CMB, ω(θ) and SNIa, we find a value of wDE consistent with -1 to a precision better than 5 per cent when it is assumed to be constant in time, and better than 6 per cent when we also allow for a spatially curved Universe. [ABSTRACT FROM AUTHOR]

We extract cosmological information from the anisotropic power-spectrummeasurements from the recently completed Baryon Oscillation Spectroscopic Survey (BOSS), extending the concept of clustering wedges to Fourier space. Making use of new fast-Fourier-transform-based estimators, we measure the power-spectrum clustering wedges of the BOSS sample by filtering out the information of Legendre multipoles ℓ > 4. Our modelling of these measurements is based on novel approaches to describe non-linear evolution, bias and redshift-space distortions, which we test using synthetic catalogues based on large-volume N-body simulations. We are able to include smaller scales than in previous analyses, resulting in tighter cosmological constraints. Using three overlapping redshift bins, we measure the angular-diameter distance, the Hubble parameter and the cosmic growth rate and explore the cosmological implications of our full-shape clustering measurements in combination with cosmic microwave background and Type Ia supernova data. Assuming a Λ cold dark matter (ΛCDM) cosmology, we constrain the matter density #8230; and the Hubble parameter to #8230; , at a confidence level of 68 per cent. We also allow for nonstandard dark energy models and modifications of the growth rate, finding good agreement with the ΛCDM paradigm. For example, we constrain the equation-of-state parameter to #8230;. This paper is part of a set that analyses the final galaxy-clustering data set from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. to produce the final cosmological constraints from BOSS. [ABSTRACT FROM AUTHOR]

We explore the cosmological implications of anisotropic clustering measurements in configuration space of the final galaxy samples from Data Release 12 of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey. We implement a new detailed modelling of the effects of non-linearities, bias and redshift-space distortions that can be used to extract unbiased cosmological information from our measurements for scales s ≳ 20 h-1 Mpc. We combined the information from Baryon Oscillation Spectroscopic Survey (BOSS) with the latest cosmic microwave background (CMB) observations and Type Ia supernovae samples and found no significant evidence for a deviation from the Λ cold dark matter (ΛCDM) cosmological model. In particular, these data sets can constrain the dark energy equationof- state parameter to wDE = -0.996 ± 0.042 when to be assumed time independent, the curvature of the Universe to Ωk = -0.0007 ± 0.0030 and the sum of the neutrino masses to ∑m2 < 0.25 eV at 95 per cent confidence levels. We explore the constraints on the growth rate of cosmic structures assuming f(z)=Ωm(z)γ and obtain γ =0.609±0.079, in good agreement with the predictions of general relativity of γ = 0.55. We compress the information of our clustering measurements into constraints on the parameter combinations DV(z)/rd, FAP(z) and ƒσ8(z) at zeff = 0.38, 0.51 and 0.61 with their respective covariance matrices and find good agreement with the predictions for these parameters obtained from the best-fitting ΛCDM model to the CMB data from the Planck satellite. This paper is part of a set that analyses the final galaxy clustering data set from BOSS. The measurements and likelihoods presented here are combined with others by Alam et al. to produce the final cosmological constraints from BOSS. [ABSTRACT FROM AUTHOR]

The cosmological information contained in anisotropic galaxy clustering measurements can often be compressed into a small number of parameters whose posterior distribution is well described by a Gaussian. We present a general methodology to combine these estimates into a single set of consensus constraints that encode the total information of the individual measurements, taking into account the full covariance between the different methods. We illustrate this technique by applying it to combine the results obtained from different clustering analyses, including measurements of the signature of baryon acoustic oscillations and redshiftspace distortions, based on a set of mock catalogues of the final SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Our results show that the region of the parameter space allowed by the consensus constraints is smaller than that of the individual methods, highlighting the importance of performing multiple analyses on galaxy surveys even when the measurements are highly correlated. This paper is part of a set that analyses the final galaxy clustering data set from BOSS. The methodology presented here is used in Alam et al. to produce the final cosmological constraints from BOSS. [ABSTRACT FROM AUTHOR]

We explore the cosmological implications of anisotropic clustering measurements in configuration space of the final galaxy samples from Data Release 12 of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey. We implement a new detailed modelling of the effects of non-linearities, bias and redshift-space distortions that can be used to extract unbiased cosmological information from our measurements for scales s ≳ 20 h-1 Mpc. We combined the information from Baryon Oscillation Spectroscopic Survey (BOSS) with the latest cosmic microwave background (CMB) observations and Type Ia supernovae samples and found no significant evidence for a deviation from the A cold dark matter (ACDM) cosmological model. In particular, these data sets can constrain the dark energy equationof-state parameter to wDE = -0.996 ± 0.042 when to be assumed time independent, the curvature of the Universe to Ωk = -0.0007 ± 0.0030 and the sum of the neutrino masses to Σmv < 0.25 eV at 95 per cent confidence levels. We explore the constraints on the growth rate of cosmic structures assuming f(z)=Ωm(z)γ and obtain γ =0.609±0.079, in good agreement with the predictions of general relativity of γ = 0.55. We compress the information of our clustering measurements into constraints on the parameter combinations DV(z)/rd, FAP(z) and fσ8(z) at zeff = 0.38, 0.51 and 0.61 with their respective covariance matrices and find good agreement with the predictions for these parameters obtained from the best-fitting ACDM model to the CMB data from the Planck satellite. This paper is part of a set that analyses the final galaxy clustering data set from BOSS. The measurements and likelihoods presented here are combined with others by Alam et al. to produce the final cosmological constraints from BOSS. [ABSTRACT FROM AUTHOR]

The cosmological information contained in anisotropic galaxy clustering measurements can often be compressed into a small number of parameters whose posterior distribution is well described by a Gaussian. We present a general methodology to combine these estimates into a single set of consensus constraints that encode the total information of the individual measurements, taking into account the full covariance between the different methods. We illustrate this technique by applying it to combine the results obtained from different clustering analyses, including measurements of the signature of baryon acoustic oscillations and redshiftspace distortions, based on a set of mock catalogues of the final SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Our results show that the region of the parameter space allowed by the consensus constraints is smaller than that of the individual methods, highlighting the importance of performing multiple analyses on galaxy surveys even when the measurements are highly correlated. This paper is part of a set that analyses the final galaxy clustering data set from BOSS. The methodology presented here is used in Alam et al. to produce the final cosmological constraints from BOSS. [ABSTRACT FROM AUTHOR]

Measurements of the redshift-space galaxy clustering have been a prolific source of cosmological information in recent years. Accurate covariance estimates are an essential step for the validation of galaxy clustering models of the redshift-space two-point statistics. Usually, only a limited set of accurate N-body simulations is available. Thus, assessing the data covariance is not possible or only leads to a noisy estimate. Further, relying on simulated realizations of the survey data means that tests of the cosmology dependence of the covariance are expensive. With these points in mind, this work presents a simple theoretical model for the linear covariance of anisotropic galaxy clustering observations with synthetic catalogues. Considering the Legendre moments ('multipoles') of the two-point statistics and projections into wide bins of the line-of-sight parameter ('clustering wedges'), we describe the modelling of the covariance for these anisotropic clustering measurements for galaxy samples with a trivial geometry in the case of a Gaussian approximation of the clustering likelihood. As main result of this paper, we give the explicit formulae for Fourier and configuration space covariance matrices. To validate our model, we create synthetic halo occupation distribution galaxy catalogues by populating the haloes of an ensemble of large-volume N-body simulations. Using linear and non-linear input power spectra, we find very good agreement between the model predictions and the measurements on the synthetic catalogues in the quasi-linear regime. [ABSTRACT FROM AUTHOR]

The estimation of cosmological constraints from observations of the large-scale structure of the Universe, such as the power spectrum or the correlation function, requires the knowledge of the inverse of the associated covariance matrix, namely the precision matrix, Ψ. In most analyses, Ψ is estimated from a limited set of mock catalogues. Depending on how many mocks are used, this estimation has an associated error which must be propagated into the final cosmological constraints. For future surveys such as Euclid and Dark Energy Spectroscopic Instrument, the control of this additional uncertainty requires a prohibitively large number of mock catalogues. In this work, we test a novel technique for the estimation of the precision matrix, the covariance tapering method, in the context of baryon acoustic oscillation measurements. Even though this technique was originally devised as a way to speed up maximum likelihood estimations, our results show that it also reduces the impact of noisy precision matrix estimates on the derived confidence intervals, without introducing biases on the target parameters. The application of this technique can help future surveys to reach their true constraining power using a significantly smaller number of mock catalogues. [ABSTRACT FROM AUTHOR]

We test the cosmological implications of studying galaxy clustering using a tomographic approach, by computing the galaxy two-point angular correlation function ω(θ) in thin redshift shells using a spectroscopic redshift galaxy survey. The advantages of this procedure are that it is not necessary to assume a fiducial cosmology in order to convert measured angular positions and redshifts into distances, and that it gives several (less accurate) measurements of the angular diameter distance DA(z) instead of only one (more precise) measurement of the effective average distance DV(z), which results in better constraints on the expansion history of the Universe. We test our model for ω(θ) and its covariance matrix against a set of mock galaxy catalogues and show that this technique is able to extract unbiased cosmological constraints. Also, assuming the best-fitting Λ cold dark matter (ΛCDM) cosmology from the cosmic microwave background measurements from the Planck satellite, we forecast the result of applying this tomographic approach to the final Baryon Oscillation Spectroscopic Survey catalogue in combination with Planck for three flat cosmological models, and compare them with the expected results of the isotropic baryon acoustic oscillation (BAO) measurements post-reconstruction on the same galaxy catalogue combined with Planck. While BAOs are more accurate for constraining cosmological parameters for the standard ΛCDM model, the tomographic technique gives better results when we allow the dark energy equation of state wDE to deviate from −1, resulting in a performance similar to BAOs in the case of a constant value of wDE, and a moderate improvement in the case of a time-dependent value of wDE, increasing the value of the figure of merit in the w0–wa plane up to 15 per cent. [ABSTRACT FROM PUBLISHER]

We report a case of Chagas disease reactivation in a patient with stage IIb follicular lymphoma in the cecum. He was admitted to the hospital with neutropenia and fever. He had a history of right hemicolectomy 6 months earlier and had received the sixth cycle of chemotherapy with cyclophosphamide/doxorubicin/vincristine/prednisone/rituximab. Blood and urine cultures were negative, but the fever persisted. Reactivation of Chagas disease was confirmed by means of quantitative real-time polymerase chain reaction (qRT-PCR). Parasitic load was 577 950 parasite equivalents/mL. The patient began treatment with benznidazole 5 mg/k per day every 12 hours. After 1 month, the qRT-PCR control was undetectable. The patient completed 60 days of treatment and is currently asymptomatic. Trypanosoma cruzi qRT-PCR may become a useful diagnostic method for reactivation of Chagas disease. [ABSTRACT FROM AUTHOR]

We present a clustering analysis of the BOSS DR12 CMASS galaxy sample, combining measurements of the galaxy two-point correlation function and density-split clustering down to a scale of |$1 \, h^{-1}\, \text{Mpc}$|⁠. Our theoretical framework is based on emulators trained on high-fidelity mock galaxy catalogues that forward model the cosmological dependence of the clustering statistics within an extended-ΛCDM framework, including redshift-space and Alcock–Paczynski distortions. Our base-ΛCDM analysis finds ωcdm = 0.1201 ± 0.0022, σ8 = 0.792 ± 0.034, and ns  = 0.970 ± 0.018, corresponding to f σ8 = 0.462 ± 0.020 at z ≈ 0.525, which is in agreement with Planck 2018 predictions and various clustering studies in the literature. We test single-parameter extensions to base-ΛCDM, varying the running of the spectral index, the dark energy equation of state, and the density of mass-less relic neutrinos, finding no compelling evidence for deviations from the base model. We model the galaxy–halo connection using a halo occupation distribution framework, finding signatures of environment-based assembly bias in the data. We validate our pipeline against mock catalogues that match the clustering and selection properties of CMASS, showing that we can recover unbiased cosmological constraints even with a volume 84 times larger than the one used in this study. [ABSTRACT FROM AUTHOR]

Voids are promising cosmological probes. Nevertheless, every cosmological test based on voids must necessarily employ methods to identify them in redshift space. Therefore, redshift-space distortions (RSD) and the Alcock–Paczyński effect (AP) have an impact on the void identification process itself generating distortion patterns in observations. Using a spherical void finder, we developed a statistical and theoretical framework to describe physically the connection between the identification in real and redshift space. We found that redshift-space voids above the shot noise level have a unique real-space counterpart spanning the same region of space, they are systematically bigger and their centres are preferentially shifted along the line of sight. The expansion effect is a by-product of RSD induced by tracer dynamics at scales around the void radius, whereas the off-centring effect constitutes a different class of RSD induced at larger scales by the global dynamics of the whole region containing the void. The volume of voids is also altered by the fiducial cosmology assumed to measure distances, this is the AP change of volume. These three systematics have an impact on cosmological statistics. In this work, we focus on the void size function. We developed a theoretical framework to model these effects and tested it with a numerical simulation, recovering the statistical properties of the abundance of voids in real space. This description depends strongly on cosmology. Hence, we lay the foundations for improvements in current models of the abundance of voids in order to obtain unbiased cosmological constraints from redshift surveys. [ABSTRACT FROM AUTHOR]

In this paper, we present COMET , a Gaussian process emulator of the galaxy power spectrum multipoles in redshift space. The model predictions are based on one-loop perturbation theory and we consider two alternative descriptions of redshift-space distortions: one that performs a full expansion of the real- to redshift-space mapping, as in recent effective field theory models, and another that preserves the non-perturbative impact of small-scale velocities by means of an effective damping function. The outputs of COMET can be obtained at arbitrary redshifts, for arbitrary fiducial background cosmologies, and for a large parameter space that covers the shape parameters ω c , ω b , and ns , as well as the evolution parameters h ,  As , Ω K , w 0, and wa. This flexibility does not impair COMET 's accuracy, since we exploit an exact degeneracy between the evolution parameters that allows us to train the emulator on a significantly reduced parameter space. While the predictions are sped up by two orders of magnitude, validation tests reveal an accuracy of |$0.1\, {{\ \rm per\ cent}}$| for the monopole and quadrupole (⁠|$0.3\, {{\ \rm per\ cent}}$| for the hexadecapole), or alternatively, better than |$0.25\, \sigma$| for all three multipoles in comparison to statistical uncertainties expected for the Euclid survey with a tenfold increase in volume. We show that these differences translate into shifts in mean posterior values that are at most of the same size, meaning that COMET can be used with the same confidence as the exact underlying models. COMET is a publicly available python package that also provides the tree-level bispectrum multipoles and Gaussian covariance matrices. [ABSTRACT FROM AUTHOR]

We report and analyse a serendipitous finding of foregrounds in the cosmic microwave background (CMB) radiation associated with extended galactic haloes. Using the cross-correlation of Planck and Wilkinson Microwave Anisotropy Probe maps and the 2MRS galaxy catalogue, we find that the mean temperature radial profiles around nearby galaxies at |$cz\le 4500~\rm {km~s^{-1}}$| show a statistically significant systematic decrease of |$\sim 15~\mu \rm {K}$| extending up to several galaxy radii. This deficit in the temperature strongly depends on the galaxy morphological type at scales within several tens of times the galaxy size, becoming nearly independent of galaxy morphology at larger scales. The effect is significantly stronger for the more extended galaxies, with galaxy clustering having a large impact on the results. Our findings indicate the presence of statistically relevant foregrounds in the CMB maps that should be considered in detailed cosmological studies. Besides, we argue that these can be used to explore the intergalactic medium surrounding bright late-type galaxies and allow for diverse astrophysical analyses. [ABSTRACT FROM AUTHOR]

This is the second part of a thorough investigation of the redshift-space effects that affect void properties and the impact they have on cosmological tests. Here, we focus on the void-galaxy cross-correlation function, specifically, on the projected versions that we developed in a previous work. The pillar of the analysis is the one-to-one relationship between real and redshift-space voids above the shot-noise level identified with a spherical void finder. Under this mapping, void properties are affected by three effects: (i) a systematic expansion as a consequence of the distortions induced by galaxy dynamics, (ii) the Alcock–Paczynski volume effect, which manifests as an overall expansion or contraction depending on the fiducial cosmology, and (iii) a systematic off-centring along the line of sight as a consequence of the distortions induced by void dynamics. We found that correlations are also affected by an additional source of distortions: the ellipticity of voids. This is the first time that distortions due to the off-centring and ellipticity effects are detected and quantified. With a simplified test, we verified that the Gaussian streaming model is still robust provided all these effects are taken into account, laying the foundations for improvements in current models in order to obtain unbiased cosmological constraints from spectroscopic surveys. Besides this practical importance, this analysis also encodes key information about the structure and dynamics of the Universe at the largest scales. Furthermore, some of the effects constitute cosmological probes by themselves, as is the case of the void ellipticity. [ABSTRACT FROM AUTHOR]

Accurate modelling of redshift-space distortions (RSD) is challenging in the non-linear regime for two-point statistics e.g. the two-point correlation function (2PCF). We take a different perspective to split the galaxy density field according to the local density, and cross-correlate those densities with the entire galaxy field. Using mock galaxies, we demonstrate that combining a series of cross-correlation functions (CCFs) offers improvements over the 2PCF as follows: (1) The distribution of peculiar velocities in each split density is nearly Gaussian. This allows the Gaussian streaming model for RSD to perform accurately within the statistical errors of a (⁠|$1.5\, h^{-1}$| Gpc)3 volume for almost all scales and all split densities. (2) The probability distribution of the density contrast at small scales is non-Gaussian, but the CCFs of split densities capture the non-Gaussianity, leading to improved cosmological constraints over the 2PCF. We can obtain unbiased constraints on the growth parameter f σ12 at the per cent level, and Alcock–Paczynski (AP) parameters at the sub-per cent level with the minimal scale of |$15\, h^{-1}{\rm Mpc}$|⁠. This is a ∼30 per cent and ∼6 times improvement over the 2PCF, respectively. The diverse and steep slopes of the CCFs at small scales are likely to be responsible for the improved constraints of AP parameters. (3) Baryon acoustic oscillations (BAO) are contained in all CCFs of split densities. Including BAO scales helps to break the degeneracy between the line-of-sight and transverse AP parameters, allowing independent constraints on them. We discuss and compare models for RSD around spherical densities. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate that the information encoded in one single (sufficiently large) N -body simulation can be used to reproduce arbitrary numbers of halo catalogues, using approximated realizations of dark matter density fields with different initial conditions. To this end, we use as a reference one realization (from an ensemble of 300) of the Minerva N -body simulations and the recently published Bias Assignment Method to extract the local and non-local bias linking the halo to the dark matter distribution. We use an approximate (and fast) gravity solver to generate 300 dark matter density fields from the down-sampled initial conditions of the reference simulation and sample each of these fields using the halo-bias and a kernel, both calibrated from the arbitrarily chosen realization of the reference simulation. We show that the power spectrum, its variance, and the three-point statistics are reproduced within |$\sim \!2{{\ \rm per\ cent}}$| (up to |$k\sim 1.0\, h\, {\rm Mpc}^{-1}$|⁠), |$\sim \!5-10{{\ \rm per\ cent}}$|⁠ , and |$\sim \!10{{\ \rm per\ cent}}$|⁠ , respectively. Using a model for the real space power spectrum (with three free bias parameters), we show that the covariance matrices obtained from our procedure lead to parameter uncertainties that are compatible within |$\sim \!10{{\ \rm per\ cent}}$| with respect to those derived from the reference covariance matrix, and motivate approaches that can help to reduce these differences to |$\sim \!1{{\ \rm per\ cent}}$|⁠. Our method has the potential to learn from one simulation with moderate volumes and high-mass resolution and extrapolate the information of the bias and the kernel to larger volumes, making it ideal for the construction of mock catalogues for present and forthcoming observational campaigns such as Euclid or DESI. [ABSTRACT FROM AUTHOR]

We present a new cosmological test using the distribution of galaxies around cosmic voids without assuming a fiducial cosmology. The test is based on a physical model for the void–galaxy cross-correlation function projected along and perpendicular to the line of sight. We treat correlations in terms of void-centric angular distances and redshift differences between void–galaxy pairs, hence it is not necessary to assume a fiducial cosmology. This model reproduces the coupled dynamical (Kaiser effect, RSD) and geometrical (Alcock–Paczynski effect, GD) distortions that affect the correlation measurements. It also takes into account the scale mixing due to the projection ranges in both directions. The model is general, so it can be applied to an arbitrary cylindrical binning scheme, not only in the case of the projected correlations. It primarily depends on two cosmological parameters: Ω m , the matter fraction of the Universe today (sensitive to GD), and β, the ratio between the growth rate factor of density perturbations and the tracer bias (sensitive to RSD). In the context of the new generation of galaxy spectroscopic surveys, we calibrated the test using the Millennium XXL simulation for different redshifts. The method successfully recovers the cosmological parameters. We studied the effect of measuring with different projection ranges, finding robust results up to wide ranges. The resulting data covariance matrices are relatively small, which reduces the noise in the Gaussian likelihood analysis and will allow the usage of a smaller number of mock catalogues. The performance evaluated in this work indicates that the developed method is a promising test to be applied on real data. [ABSTRACT FROM AUTHOR]

Measurements of redshift space distortions (RSD) provide a means to test models of gravity on large scales. We use mock galaxy catalogues constructed from large N -body simulations of standard and modified gravity models to measure galaxy clustering in redshift space. We focus our attention on two of the most representative and popular families of modified gravity models: the Hu & Sawicki f (R) gravity and the normal branch of the Dvali−Gabadadze−Porrati (DGP) model. The galaxy catalogues are built using a halo occupation distribution (HOD) prescription with the HOD parameters in the modified gravity models tuned to match with the number density and the real-space clustering of boss-cmass galaxies. We employ two approaches to model RSD: the first is based on linear perturbation theory and the second models non-linear effects on small scales by assuming standard gravity and including biasing and RSD effects. We measure the monopole to real-space correlation function ratio, the quadrupole to monopole ratio, clustering wedges, and multipoles of the correlation function and use these statistics to find the constraints on the distortion parameter, β. We find that the linear model fails to reproduce the N -body simulation results and the true value of β on scales |$s \lt 40\, h^{-1}\, {\rm Mpc}$|⁠, while the non-linear modelling of RSD recovers the value of β on the scales of interest for all models. RSD on large scales (⁠|$s\gtrsim 20\!-\!40\, h^{-1}\, {\rm Mpc}$|⁠) have been found to show significant deviations from the prediction of standard gravity in the DGP models. However, the potential to use RSD to constrain f (R) models is less promising, due to the different screening mechanism in this model. [ABSTRACT FROM AUTHOR]

We study the accuracy of several approximate methods for gravitational dynamics in terms of halo power spectrum multipoles and their estimated covariance matrix. We propagate the differences in covariances into parameter constraints related to growth rate of structure, Alcock–Paczynski distortions, and biasing. We consider seven methods in three broad categories: algorithms that solve for halo density evolution deterministically using Lagrangian trajectories (ICE–COLA, pinocchio, and peakpatch), methods that rely on halo assignment schemes on to dark matter overdensities calibrated with a target N-body run (halogen, patchy), and two standard assumptions about the full density probability distribution function (Gaussian and lognormal). We benchmark their performance against a set of three hundred N-body simulations, running similar sets of approximate simulations with matched initial conditions, for each method. We find that most methods reproduce the monopole to within |$5{{\ \rm per\ cent}}$|⁠, while residuals for the quadrupole are sometimes larger and scale dependent. The variance of the multipoles is typically reproduced within |$10{{\ \rm per\ cent}}$|⁠. Overall, we find that covariances built from approximate simulations yield errors on model parameters within |$10{{\ \rm per\ cent}}$| of those from the N-body-based covariance. [ABSTRACT FROM AUTHOR]

We measure the growth rate and its evolution using the anisotropic clustering of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 14 (DR14) quasar sample, which includes |$148\, 659$| quasars covering the wide redshift range of 0.8 < z < 2.2 and a sky area of |$2112.90\, \rm deg^2$|⁠. To optimize measurements we deploy a redshift-dependent weighting scheme, which allows us to avoid binning and perform the data analysis consistently including the redshift evolution across the sample. We perform the analysis in Fourier space, and use the redshift evolving power spectrum multipoles to measure the redshift-space distortion parameter f σ8 and parameters controlling the anisotropic projection of the cosmological perturbations. We measure f σ8(z  = 1.52) = 0.43 ± 0.05 and d f σ8/d z (z  = 1.52) = −0.16 ± 0.08, consistent with the expectation for a lambda cold dark matter cosmology as constrained by the Planck experiment. [ABSTRACT FROM AUTHOR]

We compare the measurements of the bispectrum and the estimate of its covariance obtained from a set of different methods for the efficient generation of approximate dark matter halo catalogues to the same quantities obtained from full N -body simulations. To this purpose we employ a large set of 300 realizations of the same cosmology for each method, run with matching initial conditions in order to reduce the contribution of cosmic variance to the comparison. In addition, we compare how the error on cosmological parameters such as linear and non-linear bias parameters depends on the approximate method used for the determination of the bispectrum variance. As general result, most methods provide errors within 10 per cent of the errors estimated from N -body simulations. Exceptions are those methods requiring calibration of the clustering amplitude but restrict this to 2-point statistics. Finally we test how our results are affected by being limited to a few hundreds measurements from N -body simulation by comparing with a larger set of several thousands of realizations performed with one approximate method. [ABSTRACT FROM AUTHOR]

We use baryon acoustic oscillation and redshift space distortion from the completed Baryon Oscillation Spectroscopic Survey, corresponding to Data Release 12 of the Sloan Digital Sky Survey, combined sample analysis in combination with cosmic microwave background, supernova, and redshift space distortion measurements from additional spectroscopic surveys to test deviations from general relativity. We present constraints on several phenomenological models of modified gravity: First, we parametrize the growth of structure using the growth index γ , finding γ = 0.566 ± 0.058 (68 per cent C.L.). Secondly, we modify the relation of the two Newtonian potentials by introducing two additional parameters, GM and GL. In this approach, GM refers to modifications of the growth of structure whereas GL to modification of the lensing potential. We consider a power law to model the redshift dependence of GM and GL as well as binning in redshift space, introducing four additional degrees of freedom, GM(z < 0.5), GM(z > 0.5), GL(z < 0.5), and GL(z > 0.5). At 68 per cent C.L., we measure GM = 0.980 ± 0.096 and GL = 1.082 ± 0.060 for a linear model, GM = 1.01 ± 0.36 and GL = 1.31 ± 0.19 for a cubic model as well as GM(z < 0.5) = 1.26 ± 0.32, GM(z > 0.5) = 0.986 ± 0.022, GL(z < 0.5) = 1.067 ± 0.058, and GL(z > 0.5) = 1.037 ± 0.029. Thirdly, we investigate general scalar tensor theories of gravity, finding the model to be mostly unconstrained by current data. Assuming a one-parameter f(R) model, we can constrain B0 < 7.7 × 10-5 (95 per cent C.L). For all models we considered, we find good agreement with general relativity. [ABSTRACT FROM AUTHOR]

We present distance scale measurements from the baryon acoustic oscillation signal in the constant stellar mass and low-redshift sample samples from the Data Release 12 of the Baryon Oscillation Spectroscopic Survey. The total volume probed is 14.5 Gpc³, 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 DV(z)rfidd/rd=2028±21 Mpc and a distance to z = 0.32 of DV(z)rfidd/rd=1264±22 Mpc assuming a cosmology in which rfidd=147.10 Mpc. From the anisotropic analysis, we find an angular diameter distance to z = 0.57 of DA(z)rfidd/rd=1401±21 Mpc and a distance to z = 0.32 of 981 ± 20 Mpc, a 1.5 and 2.0 per cent measurement, respectively. The Hubble parameter at z = 0.57 is H(z)rd/rfidd=100.3±3.7 km s-1 Mpc-1 and its value at z = 0.32 is 79.2 ± 5.6 km s-1 Mpc-1, a 3.7 and 7.1 per cent measurement, respectively. These cosmic distance scale constraints are in excellent agreement with a Λ cold dark matter model with cosmological parameters released by the recent Planck 2015 results. [ABSTRACT FROM AUTHOR]

We reproduce the galaxy clustering catalogue from the SDSS-III Baryon Oscillation Spectroscopic Survey Final Data Release (BOSS DR11&DR12) with high fidelity on all relevant scales in order to allow a robust analysis of baryon acoustic oscillations and redshift space distortions. We have generated (6000) 12 288 MultiDark PATCHY BOSS (DR11) DR12 light cones corresponding to an effective volume of ∼192 000 [h-1 Gpc]³ (the largest ever simulated volume), including cosmic evolution in the redshift range from 0.15 to 0.75. The mocks have been calibrated using a reference galaxy catalogue based on the halo abundance matching modelling of the BOSS DR11&DR12 galaxy clustering data and on the data themselves. The production follows three steps. First, we apply the PATCHY code to generate a dark matter field and an object distribution including non-linear stochastic galaxy bias. Secondly, we run the halo/stellar distribution reconstruction HADRON code to assign masses to the various objects. This step uses the mass distribution as a function of local density and non-local indicators (i.e. tidal field tensor eigenvalues and relative halo exclusion separation for massive objects) from the reference simulation applied to the corresponding patchy dark matter and galaxy distribution. Finally, we apply the SUGAR code to build the light cones. The resulting MultiDarkPATCHY mock light cones reproduce the number density, selection function, survey geometry, and in general within 1s, for arbitrary stellar mass bins, the power spectrum up to k = 0.3 h Mpc-1, the two-point correlation functions down to a few Mpc scales, and the three-point statistics of the BOSS DR11&DR12 galaxy samples. [ABSTRACT FROM AUTHOR]

Extraction of the Baryon Acoustic Oscillations (BAO) to per cent level accuracy is challenging and demands an understanding of many potential systematics to an accuracy well below 1 per cent, in order to ensure that they do not combine significantly when compared to statistical error of the BAO measurement. Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 11 (DR11) reaches a distance measurement with ∼1 per cent statistical error and this prompts an extensive search for all possible sub-per cent level systematic errors which could previously be safely ignored. In this paper, we analyse the potential systematics in BAO fitting methodology using mocks and data from BOSS DR10 and DR11. We demonstrate the robustness of the fiducial multipole fitting methodology to be at 0.1–0.2 per cent level with a wide range of tests in mock galaxy catalogues pre- and post-reconstruction. We also find the DR10 and DR11 data from BOSS to be robust against changes in methodology at a similar level. This systematic error budget is incorporated into the BOSS DR10 and DR11 BAO measurements. Of the wide range of changes we have investigated, we find that when fitting post-reconstructed data or mocks, the only change which has an effect >0.1 per cent on the best-fitting values of distance measurements is varying the order of the polynomials to describe the broad-band terms (∼0.2 per cent). Finally, we compare an alternative methodology denoted as Clustering Wedges with Multipoles, and find that it is consistent with the standard approach. [ABSTRACT FROM PUBLISHER]

We investigate the cosmological implications of the latest growth of structure measurement from the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS Data Release 11 with particular focus on the sum of the neutrino masses, ∑mν. We examine the robustness of the cosmological constraints from the baryon acoustic oscillation (BAO) scale, the Alcock–Paczynski effect and redshift-space distortions (DV/rs, FAP, fσ8) of Beutler et al., when introducing a neutrino mass in the power spectrum template. We then discuss how the neutrino mass relaxes discrepancies between the cosmic microwave background (CMB) and other low-redshift measurements within Λ cold dark matter. Combining our cosmological constraints with 9-year Wilkinson Microwave Anisotropy Probe (WMAP9) yields ∑mν = 0.36 ± 0.14 eV (68 per cent c.l.), which represents a 2.6σ preference for non-zero neutrino mass. The significance can be increased to 3.3σ when including weak lensing results and other BAO constraints, yielding ∑mν = 0.35 ± 0.10 eV (68 per cent c.l.). However, combining CMASS with Planck data reduces the preference for neutrino mass to ∼2σ. When removing the CMB lensing effect in the Planck temperature power spectrum (by marginalizing over AL), we see shifts of ∼1σ in σ8 and Ωm, which have a significant effect on the neutrino mass constraints. In the case of CMASS plus Planck without the AL lensing signal, we find a preference for a neutrino mass of ∑mν = 0.34 ± 0.14 eV (68 per cent c.l.), in excellent agreement with the WMAP9+CMASS value. The constraint can be tightened to 3.4σ yielding ∑mν = 0.36 ± 0.10 eV (68 per cent c.l.) when weak lensing data and other BAO constraints are included. [ABSTRACT FROM AUTHOR]

We analyse the anisotropic clustering of the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS Data Release 11 (DR11) sample, which consists of 690 827 galaxies in the redshift range 0.43 < z < 0.7 and has a sky coverage of 8498 deg2. We perform our analysis in Fourier space using a power spectrum estimator suggested by Yamamoto et al. We measure the multipole power spectra in a self-consistent manner for the first time in the sense that we provide a proper way to treat the survey window function and the integral constraint, without the commonly used assumption of an isotropic power spectrum and without the need to split the survey into subregions. The main cosmological signals exploited in our analysis are the baryon acoustic oscillations and the signal of redshift space distortions, both of which are distorted by the Alcock–Paczynski effect. Together, these signals allow us to constrain the distance ratio DV(zeff)/rs(zd) = 13.89 ± 0.18, the Alcock–Paczynski parameter FAP(zeff) = 0.679 ± 0.031 and the growth rate of structure f (zeff)σ8(zeff) = 0.419 ± 0.044 at the effective redshift zeff = 0.57. We emphasize that our constraints are robust against possible systematic uncertainties. In order to ensure this, we perform a detailed systematics study against CMASS mock galaxy catalogues and N-body simulations. We find that such systematics will lead to 3.1 per cent uncertainty for fσ8 if we limit our fitting range to k = 0.01–0.20 h Mpc−1, where the statistical uncertainty is expected to be three times larger. We did not find significant systematic uncertainties for DV/rs or FAP. Combining our data set with Planck to test General Relativity (GR) through the simple γ-parametrization, where the growth rate is given by $f(z) = \Omega ^{\gamma }_{\rm m}(z)$, reveals a ∼2σ tension between the data and the prediction by GR. The tension between our result and GR can be traced back to a tension in the clustering amplitude σ8 between CMASS and Planck. [ABSTRACT FROM PUBLISHER]

Sound waves from the primordial fluctuations of the Universe imprinted in the large-scale structure, called baryon acoustic oscillations (BAOs), can be used as standard rulers to measure the scale of the Universe. These oscillations have already been detected in the distribution of galaxies. Here we propose to measure BAOs from the troughs (minima) of the density field. Based on two sets of accurate mock halo catalogues with and without BAOs in the seed initial conditions, we demonstrate that the BAO signal cannot be obtained from the clustering of classical disjoint voids, but it is clearly detected from overlapping voids. The latter represent an estimate of all troughs of the density field. We compute them from the empty circumsphere centers constrained by tetrahedra of galaxies using Delaunay triangulation. Our theoretical models based on an unprecedented large set of detailed simulated void catalogues are remarkably well confirmed by observational data. We use the largest recently publicly available sample of luminous red galaxies from SDSS-III BOSS DR11 to unveil for the first time a > 3σ BAO detection from voids in observations. Since voids are nearly isotropically expanding regions, their centers represent the most quiet places in the Universe, keeping in mind the cosmos origin and providing a new promising window in the analysis of the cosmological large-scale structure from galaxy surveys. [ABSTRACT FROM AUTHOR]