Redshift Space Distortion Measurements Research Articles

Model-independent reconstruction of growth index via Gaussian process

In this paper, the reconstructed growth index is updated by jointed combination from Pantheon+ SNe Ia samples, the observed Hubble data points H(z) at the background level, and redshift space distortion measurements of at the linear perturbation level via Gaussian process. The reconstructed results show that the currently available data points suggest a mild time varying growth index at low redshifts within 3σ regions. No significant deviation from ΛCDM cosmology in GR within 3σ regions was found, while the growth indices for the f(R) and the Dvali–Gabadadze–Porrati gravity are at the boundaries of 3σ regions.

Inflationary potential as seen from different angles: model compatibility from multiple CMB missions

The cosmic microwave background (CMB) temperature and polarization anisotropies, as observed by independent astronomical missions such as WMAP, Planck, and most recently the Atacama Cosmology Telescope and the South Pole Telescope have played a vital role in accurately constraining cosmological theories and models, establishing cosmic inflation as the most widely accepted theory for describing the physics of the early Universe. However, the absence of a definitive detection of B-mode polarization and the emerging discrepancies among different CMB experiments present a challenge in determining which inflationary models best explain the observed data. In this work, we further explore this difficulty and conduct a case study by analyzing four well-known inflationary potentials in light of the latest CMB temperature and polarization anisotropy measurements and lensing data released by the Planck satellite and the Atacama Cosmology Telescope. Additionally, we incorporate B-modes polarization data from the BICEP/Keck Collaboration, as well as Baryon Acoustic Oscillations and Redshift Space Distortions measurements from BOSS DR12 and eBOSS DR16. We show that the most typical models such as Starobinsky and α-attractors are in disagreement with the Atacama Cosmology Telescope small-scale CMB measurements, particularly when combined with B-modes polarization data. On the other hand, these potentials are in perfect agreement with the Planck measurements at larger angular scales. This dichotomy makes it challenging to identify a single model or a group of models that can be universally considered as the preferred choice based on all available CMB observations.

Isolating the linear signal when making redshift space distortion measurements

ABSTRACT Constraints on the linear growth rate, fσ8, using small-scale redshift space distortion measurements have a significant statistical advantage over those made on large scales. However, these measurements need to carefully disentangle the linear and non-linear information when interpreting redshift space distortions in terms of fσ8. It is particularly important to do this given that some previous measurements found a significant deviation from the expectation based on the Lambda cold dark matter (ΛCDM) model constrained by Planck cosmic microwave background data. We construct a new emulator-based model for small-scale galaxy clustering with scaling parameters for both the linear and non-linear velocities of galaxies, allowing us to isolate the linear growth rate. We train the emulator using simulations from the AbacusCosmos suite, and apply it to data from the extended Baryon Oscillation Spectroscopic Survey luminous red galaxy sample. We obtain a value of fσ8(z = 0.737) = 0.368 ± 0.041, in 2.3σ tension with the Planck 2018 ΛCDM expectation, and find less dependence on the minimum measurement scale than previous analyses.

Updating constraints on phantom crossing f(T) gravity

We establish constraints on f(T) gravity by considering the possibility of a scenario that supports a phantom crossing of the equation of state parameter ω DE. After determining the viable parameter space of the model, while checking the impact on the background dynamics, we perform an analysis to obtain constraints on cosmological parameters and determine the viability of this scenario. To this end, we use combined data sets from cosmic chronometers (CC), baryonic acoustic oscillations (BAO), redshift space distortion (RSD) and Type Ia supernovae (SN) measurements from the latest Pantheon+ set, in which the impact on the absolute magnitude due to the change of the effective gravitational constant is also considered. It is found that a state where a phantom crossing of ω DE happens is favored by data, and the f(T) model is competitive with the ΛCDM one by statistical criteria, such as AIC and BIC. Additionally, we find evidence of the Hubble tension being alleviated within the f(T) model, at the same time that it does not worsen the growth one, indicating a possibility of the present scenario as an option to address the current cosmic tensions.

Testing the growth rate in homogeneous and inhomogeneous interacting vacuum models

In this work we consider a class of interacting vacuum corresponding to a generalised Chaplygin gas (gCg) cosmology. In particular we analyse two different scenarios at perturbation level for the same background interaction characterised by the parameter α: (i) matter that follows geodesics, corresponding to homogeneous vacuum, and (ii) a covariant ansatz for vacuum density perturbations. In the latter case, we show that the vacuum perturbations are very tiny as compared to matter perturbations on sub-horizon scales. In spite of that, depending on the value of the Chaplygin gas parameter α, vacuum perturbations suppress or enhance the matter growth rate as compared to the case (i). We use Cosmic Microwave Background (CMB), type Ia supernovae (SNe) and Redshift Space Distortion (RSD) measurements to test the observational viability of the model. We found that the mean value of our joint analysis clearly favours a positive interaction, i.e., an energy flux from dark matter to dark energy, with α ≈ 0.143 in both cases, while the cosmological standard model, recovered for α = 0, is ruled out by 3σ confidence level. Noteworthy, the positive value of interaction can alleviate both the H 0 and S 8 tension for the dataset considered here.

The DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation

Over the next 5 yr, the Dark Energy Spectroscopic Instrument (DESI) will use 10 spectrographs with 5000 fibers on the 4 m Mayall Telescope at Kitt Peak National Observatory to conduct the first Stage IV dark energy galaxy survey. At z < 0.6, the DESI Bright Galaxy Survey (BGS) will produce the most detailed map of the universe during the dark-energy-dominated epoch with redshifts of >10 million galaxies spanning 14,000 deg2. In this work, we present and validate the final BGS target selection and survey design. From the Legacy Surveys, BGS will target an r < 19.5 mag limited sample (BGS Bright), a fainter 19.5 < r < 20.175 color-selected sample (BGS Faint), and a smaller low-z quasar sample. BGS will observe these targets using exposure times scaled to achieve homogeneous completeness and cover the footprint three times. We use observations from the Survey Validation programs conducted prior to the main survey along with simulations to show that BGS can complete its strategy and make optimal use of “bright” time. BGS targets have stellar contamination <1%, and their densities do not depend strongly on imaging properties. BGS Bright will achieve >80% fiber assignment efficiency. Finally, BGS Bright and BGS Faint will achieve >95% redshift success over any observing condition. BGS meets the requirements for an extensive range of scientific applications. BGS will yield the most precise baryon acoustic oscillation and redshift-space distortion measurements at z < 0.4. It presents opportunities for new methods that require highly complete and dense samples (e.g., N-point statistics, multitracers). BGS further provides a powerful tool to study galaxy populations and the relations between galaxies and dark matter.

Velocity profiles of matter and biased tracers around voids

ABSTRACT The velocity profile of galaxies around voids is a key ingredient for redshift space distortion (RSD) measurements made using the void–galaxy correlation function. In this paper, we use simulations to test whether the velocity profile of the tracers used to find the voids matches the velocity profile of the dark matter around these voids. A mismatch is expected and found in the inner part of voids, where tracers are very sparse. We discuss how this difference is caused by a selection effect where the void centre positions are correlated to the particular realization of the sparse tracers and their spatial distribution. In turn, this then affects the RSD void–galaxy correlation analysis. We show this by evaluating the Jacobian of the real to redshift space mapping using the tracer or matter velocity profile. Differences of the order of 20 per cent in the velocity profile translate into differences of the order of few per cent in the Jacobian. This small discrepancy propagates to the monopole and quadrupole of the void–tracer correlation function, producing modifications of comparable magnitude to those from changes in fσ8 at the level of the statistical uncertainties from current analyses.

A non-linear solution to the S8 tension?

ABSTRACT Weak galaxy lensing surveys have consistently reported a lower amplitude for the matter fluctuation spectrum, as measured by the S8 parameter, than expected in the ΛCDM cosmology favoured by Planck. However, the expansion history follows the predictions of the Planck ΛCDM cosmology to high accuracy, as do measurements of lensing of the cosmic microwave background anisotropies. Redshift space distortion measurements also appear to be consistent with Planck ΛCDM. In this paper, we argue that these observations can be reconciled with the Planck ΛCDM cosmology if the matter power spectrum is suppressed more strongly on non-linear scales than assumed in analyses of weak galaxy lensing. We demonstrate this point by fitting a one-parameter model, characterizing a suppression of the non-linear power spectrum, to the KiDS-1000 weak lensing measurements. Such a suppression could be attributed to new properties of the dark matter that affect non-linear scales, or to a response of the matter fluctuations to baryonic feedback processes that are stronger than expected from recent cosmological simulations. Our proposed explanation can be tested using measurements of the amplitude of the matter fluctuation spectrum on linear scales, in particular via high precision redshift space distortion measurements from forthcoming galaxy and quasar redshift surveys.

Tightening geometric and dynamical constraints on dark energy and gravity: Galaxy clustering, intrinsic alignment, and kinetic Sunyaev-Zel’dovich effect

Conventionally, in galaxy surveys, cosmological constraints on the growth and expansion history of the Universe have been obtained from the measurements of redshift-space distortions and baryon acoustic oscillations embedded in the large-scale galaxy density field. In this paper, we study how well one can improve the cosmological constraints from the combination of the galaxy density field with velocity and tidal fields, which are observed via the kinetic Sunyaev-Zel'dovich (kSZ) and galaxy intrinsic alignment (IA) effects, respectively. For illustration, we consider the deep galaxy survey by Subaru Prime Focus Spectrograph, whose survey footprint perfectly overlaps with the imaging survey of the Hyper Suprime-Cam and the CMB-S4 experiment. We find that adding the kSZ and IA effects significantly improves cosmological constraints, particularly when we adopt the nonflat cold dark matter model which allows both time variation of the dark energy equation-of-state and deviation of the gravity law from general relativity. Under this model, we achieve 31% improvement for the growth index $\ensuremath{\gamma}$ and $&gt;35%$ improvement for other parameters except for the curvature parameter, compared to the case of the conventional galaxy-clustering-only analysis. As another example, we also consider the wide Galaxy survey by the Euclid satellite, in which shapes of galaxies are noisier but the survey volume is much larger. We demonstrate that when the above model is adopted, the clustering analysis combined with kSZ and IA from the deep survey can achieve tighter cosmological constraints than the clustering-only analysis from the wide survey.

A New Consistency Test for ΛCDM Cosmology Using Galaxy Surveys

We propose a new consistency test for the ΛCDM cosmology using baryonic acoustic oscillations (BAO) and redshift space distortion (RSD) measurements from galaxy redshift surveys. Specifically, we determine the peak position of f σ 8(z) in redshift z offered by an RSD measurement, and compare it to the one predicted by the BAO observables assuming a flat ΛCDM cosmology. We demonstrate this new test using the simulated data for the DESI galaxy survey, and argue that this test complements those using the background observables alone, and is less subject to systematics in the RSD analysis, compared to traditional methods using values of f σ 8(z) directly.

Linear growth of structure in projected massive gravity

In the present paper we investigate the linear growth of matter fluctuations based on a concrete model of the projected massive gravity, which is free of the Boulware-Deser ghost and preserves the global Lorentz symmetry. We found that at subhorizon scales, the modification to the linear growth is strongly suppressed even without nonlinear screening of an additional force. In addition, we obtain observational constraints from distance and redshift space distortion measurements and find that there is a parameter region that is consistent both observationally and theoretically.

ShapeFit: extracting the power spectrum shape information in galaxy surveys beyond BAO and RSD

In the standard (classic) approach, galaxy clustering measurements from spectroscopic surveys are compressed into baryon acoustic oscillations and redshift space distortions measurements, which in turn can be compared to cosmological models. Recent works have shown that avoiding this intermediate step and fitting directly the full power spectrum signal (full modelling) leads to much tighter constraints on cosmological parameters. Here we show where this extra information is coming from and extend the classic approach with one additional effective parameter, such that it captures, effectively, the same amount of information as the full modelling approach, but in a model-independent way. We validate this new method (ShapeFit) on mock catalogs, and compare its performance to the full modelling approach finding both to deliver equivalent results. The ShapeFit extension of the classic approach promotes the standard analyses at the level of full modelling ones in terms of information content, with the advantages of i) being more model independent; ii) offering an understanding of the origin of the extra cosmological information; iii) allowing a robust control on the impact of observational systematics.

Closing up the cluster tension?

The excellent measurements of the cosmic microwave background (CMB) fluctuations by Planck allow us to tightly constrain the amplitude of matter fluctuations at redshift ∼1100 in the Λ-cold dark matter (ΛCDM) model. This amplitude can be extrapolated to the present epoch, yielding constraints on the value of the σ8 parameter. On the other hand, the abundance of Sunyaev-Zeldovich (SZ) clusters detected by Planck, with masses inferred using a hydrostatic equilibrium assumption, leads to a significantly lower value of the same parameter. This discrepancy is often dubbed the σ8 tension in the literature and is sometimes regarded as a possible sign of new physics. Here, we examine a direct determination of σ8 at the present epoch in ΛCDM, and thereby the cluster mass calibrations using cosmological data at low redshift, namely the measurements of fσ8 from the analysis of the completed Sloan Digital Sky Survey. We combined redshift-space distortion measurements with Planck CMB constraints, X-ray, and SZ cluster counts within the ΛCDM framework, but leaving the present-day amplitude of matter fluctuations as an independent parameter (i.e. no extrapolation is made from high-redshift CMB constraints). The calibration of X-ray and SZ masses are left as free parameters throughout the whole analysis. Our study yields tight constraints on the aforementioned calibrations, with values entirely consistent with results obtained from the full combination of CMB and cluster data only. Such an agreement suggests an absence of tension in the ΛCDM model between CMB-based estimates of σ8 and constraints from low-redshift on fσ8; however, it also indicates tension with the standard calibration of clusters masses.

Minimal theory of massive gravity in the light of CMB data and the S8 tension

We investigate the minimal theory of massive gravity (MTMG) in the light of different observational datasets that are in tension within the $\mathrm{\ensuremath{\Lambda}}$ cold dark matter cosmology. In particular, we analyze the MTMG model, for the first time, with the Planck--cosmic microwave background (CMB) data, and how these precise measurements affect the free parameters of the theory. The MTMG model can affect the CMB power spectrum at large angular scales and cause a suppression on the amplitude of the matter power spectrum. We find that on adding Planck-CMB data, the graviton has a small, positive, but nonzero mass at 68% confidence level, and from this perspective, we show that the tension between redshift space distortions measurements and Planck-CMB data in the parametric space ${S}_{8}\ensuremath{-}{\mathrm{\ensuremath{\Omega}}}_{m}$ can be resolved within the MTMG scenario. Through a robust and accurate analysis, we find that the ${H}_{0}$ tension between the CMB and the local distance ladder measurements still remains but can be reduced to $\ensuremath{\sim}3.5\ensuremath{\sigma}$ within the MTMG theory. The MTMG is very well consistent with the CMB observations, and undoubtedly, it can serve as a viable candidate among other modified gravity theories.

Probing gravity with the DES-CMASS sample and BOSS spectroscopy

ABSTRACT The DES-CMASS sample (DMASS) is designed to optimally combine the weak lensing measurements from the Dark Energy Survey (DES) and redshift-space distortions (RSD) probed by the CMASS galaxy sample from the Baryonic Oscillation Spectroscopic Survey. In this paper, we demonstrate the feasibility of adopting DMASS as the equivalent of CMASS for a joint analysis of DES and BOSS in the framework of modified gravity. We utilize the angular clustering of the DMASS galaxies, cosmic shear of the DES metacalibration sources, and cross-correlation of the two as data vectors. By jointly fitting the combination of the data with the RSD measurements from the CMASS sample and Planck data, we obtain the constraints on modified gravity parameters $\mu _0=-0.37^{+0.47}_{-0.45}$ and $\Sigma _0=0.078^{+0.078}_{-0.082}$. Our constraints of modified gravity with DMASS are tighter than those with the DES Year 1 redMaGiC sample with the same external data sets by 29 per cent for μ0 and 21 per cent for Σ0, and comparable to the published results of the DES Year 1 modified gravity analysis despite this work using fewer external data sets. This improvement is mainly because the galaxy bias parameter is shared and more tightly constrained by both CMASS and DMASS, effectively breaking the degeneracy between the galaxy bias and other cosmological parameters. Such an approach to optimally combine photometric and spectroscopic surveys using a photometric sample equivalent to a spectroscopic sample can be applied to combining future surveys having a limited overlap such as DESI and LSST.

Testing large-scale structure measurements against Fisher matrix predictions

We compare Baryonic Acoustic Oscillation (BAO) and Redshift Space Distortion (RSD) measurements from recent galaxy surveys with their Fisher matrix based predictions. Measurements of the position of the BAO signal lead to constraints on the comoving angular diameter distance DM and the Hubble distance DH that agree well with their Fisher matrix based expectations. However, RSD-based measurements of the growth rate fσ8 do not agree with the predictions made before the surveys were undertaken, even when repeating those predictions using the actual survey parameters. We show that this is due to a combination of effects including degeneracies with the geometric parameters DM and DH , and optimistic assumptions about the scale to which the linear signal can be extracted. We show that measurements using current data and large-scale modelling techniques extract an equivalent amount of signal to that in the linear regime for k ≲ 0.08 h Mpc-1, remarkably independent of the sample properties and redshifts covered.

Kinematics of Mg ii absorbers from the redshift-space distortion around massive quiescent galaxies

ABSTRACT The kinematics of Mg ii absorbers is the key to understanding the origin of cool, metal-enriched gas clouds in the circumgalactic medium of massive quiescent galaxies. Exploiting the fact that the cloud line-of-sight velocity distribution is the only unknown for predicting the redshift-space distortion (RSD) of Mg ii absorbers from their 3D real-space distribution around galaxies, we develop a novel method to infer the cool cloud kinematics from the redshift-space galaxy–cloud cross-correlation ξs. We measure ξs for ∼104 Mg ii absorbers around ∼8 × 105 CMASS galaxies at 0.4 &amp;lt; z &amp;lt; 0.8. We discover that ξs does not exhibit a strong Fingers-of-God effect, but is heavily truncated at velocity ${\sim }300\, \mathrm{km}\, {\rm s}^{-1}$. We reconstruct both the redshift and real-space cloud number density distributions inside haloes, $\xi ^{s}_{1h}$ and ξ1h, respectively. Thus, for any model of cloud kinematics, we can predict $\xi ^{s}_{1h}$ from the reconstructed ξ1h, and self-consistently compare to the observed $\xi ^{s}_{1h}$. We consider four types of cloud kinematics, including an isothermal model with a single velocity dispersion, a satellite infall model in which cool clouds reside in the subhaloes, a cloud accretion model in which clouds follow the cosmic gas accretion, and a tired wind model in which clouds originate from the galactic wind-driven bubbles. All the four models provide statistically good fits to the RSD data, but only the tired wind model can reproduce the observed truncation by propagating ancient wind bubbles at ${\sim }250\, \mathrm{km}\, s^{-1}$ on scales ${\sim }400\, \, h^{-1}\, \mathrm{kpc}$. Our method provides an exciting path to decoding the dynamical origin of metal absorbers from the RSD measurements with upcoming spectroscopic surveys.

Arbitrating the S8 discrepancy with growth rate measurements from redshift-space distortions

ABSTRACT Within the Lambda cold dark matter (ΛCDM) model, measurements from recent cosmic microwave background (CMB) and weak lensing (WL) surveys have uncovered a ∼3σ disagreement in the inferred value of the parameter $S_8 \equiv \sigma _8\sqrt{\Omega _\mathrm{ m}/0.3}$, quantifying the amplitude of late-time matter fluctuations. Before questioning whether the S8 discrepancy calls for new physics, it is important to assess the view of measurements other than CMB and WL ones on the discrepancy. Here, we examine the role of measurements of the growth rate f(z) in arbitrating the S8 discrepancy, considering measurements of fσ8(z) from redshift-space distortions (RSDs). Our baseline analysis combines RSD measurements with geometrical measurements from baryon acoustic oscillations (BAO) and Type Ia Supernovae (SNeIa), given the key role of the latter in constraining Ωm. From this combination and within the ΛCDM model, we find $S_8 = 0.762^{+0.030}_{-0.025}$, and quantify the agreement between RSD + BAO + SNeIa and Planck to be at the 2.2σ level: the mild disagreement is therefore compatible with a statistical fluctuation. We discuss combinations of RSD measurements with other data sets, including the EG statistic. This combination increases the discrepancy with Planck, but we deem it significantly less robust. Our earlier results are stable against an extension where we allow the dark energy equation of state w to vary. We conclude that, from the point of view of combined growth rate and geometrical measurements, there are hints, but no strong evidence yet, for the Planck ΛCDM cosmology overpredicting the amplitude of matter fluctuations at redshifts z ≲ 1. From this perspective, it might therefore still be premature to claim the need for new physics from the S8 discrepancy.

Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory

We present the cosmological implications from final measurements of clustering using galaxies, quasars, and Ly$\alpha$ forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in large-scale structure. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, $r_d$, from eight different samples and six measurements of the growth rate parameter, $f\sigma_8$, from redshift-space distortions (RSD). This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, $\Lambda$CDM model that allows for curvature. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization the BAO data provide nearly an order of magnitude improvement on curvature constraints. The RSD measurements indicate a growth rate that is consistent with predictions from Planck primary data and with General Relativity. When combining the results of SDSS BAO and RSD with external data, all multiple-parameter extensions remain consistent with a $\Lambda$CDM model. Regardless of cosmological model, the precision on $\Omega_\Lambda$, $H_0$, and $\sigma_8$, remains at roughly 1\%, showing changes of less than 0.6\% in the central values between models. The inverse distance ladder measurement under a o$w_0w_a$CDM yields $H_0= 68.20 \pm 0.81 \, \rm km\, s^{-1} Mpc^{-1}$, remaining in tension with several direct determination methods. (abridged)

Using GAMA to probe the impact of small-scale galaxy physics on nonlinear redshift-space distortions

ABSTRACT We present improved modelling of the redshift-space distortions (RSDs) of galaxy clustering that arise from peculiar velocities. We create mock galaxy catalogues in the framework of the halo model, using data from the Bolshoi project. These mock galaxy populations are inserted into the haloes with additional degrees of freedom that govern spatial and kinematical biases of the galaxy populations relative to the dark matter. We explore this generalized halo model with an Markov Chain Monte Carlo (MCMC) algorithm, comparing the predictions to data from the Galaxy And Mass Assembly survey, and thus derive one of the first constraints on the detailed kinematic degrees of freedom for satellite galaxies within haloes. With this approach, the distortions of the redshift-space galaxy autocorrelations can be accounted for down to spatial separations close to 10 kpc, opening the prospect of improved RSD measurements of the perturbation growth rate by the inclusion of data from nonlinear scales.