Dark Energy Constraints Research Articles

Dark energy constraints from Pantheon+ Ia supernovae data

Dark energy constraints from Pantheon+ Ia supernovae data

Early dark energy constraints with late-time expansion marginalization

Early dark energy (EDE) is an extension to the ΛCDM model that includes an additional energy density contribution near recombination. The model was proposed to reduce the tension between the measurements of the Hubble constant H 0 from the cosmic microwave background (CMB) and from the local cosmic distance ladder. Some analyses in the recent literature have shown intriguing hints for EDE. However, this model increases the tension in the derived clustering of galaxies (as measured by the so-called S 8 parameter) between CMB and large scale structure (LSS) measurements. This new tension limits the contribution of EDE during recombination, and thus its effect on the Hubble tension. In this work, we investigate whether the inclusion of a general, smooth late-time dark energy modification can increase back the EDE contribution when LSS data is included in the analysis. In order to generalize the late expansion with respect to the ΛCDM model, we substitute the cosmological constant by a late dark energy fluid model with a piecewise constant equation of state w(z) in redshift bins. We show that, when analysing this generalized model with combinations of CMB, LSS and type Ia supernovae data from several experiments no significant changes on S 8 and EDE parameter constraints is found. The contribution to the EDE fraction constraint with late-time expansion marginalization is f EDE = 0.067+0.019 -0.027 using 3 redshift bins, with similar results for 5 and 10 redshift bins. This work shows that in order to solve simultaneously the Hubble and S 8 tensions, one needs a mechanism for increasing the clustering of matter at late times different from a simple change in the background evolution of late dark energy.

Modified CPL models for dark energy and observational constraints

In this work, we consider two modified Chevallier–Polarski–Linder (CPL) models in the background of homogeneous and isotropic Friedmann–Lemaître–Robertson–Walker (FLRW) space–time, namely, (i) the generalized CPL model (Model I) and (ii) the logarithmic form of the equation of state for the dark energy. From the observational data sets [Formula: see text], we find that at the present epoch (redshift [Formula: see text]), the equation of state for the dark energy converges almost at the same value [Formula: see text] and the variation of [Formula: see text] with respect to the redshift parameter is very small for both models. We also find that the present value of the Hubble parameter [Formula: see text] is almost same for both the models. Finally, we compare the models in the light of Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC) and Bayesian evidence. However, we find that Model II is better compared to Model I from the estimated value of the deceleration parameter.

Future prospects on testing extensions to ΛCDM through the weak lensing of gravitational waves

With planned space-based and 3rd generation ground-based gravitational wave detectors (LISA, Einstein Telescope, Cosmic Explorer), and proposed DeciHz detectors (DECIGO, Big Bang Observer), it is timely to explore statistical cosmological tests that can be employed with the forthcoming plethora of data, $10^4-10^6$ mergers a year. We forecast the combination of the standard siren measurement with the weak lensing of gravitational waves from binary mergers. For 10 years of 3rd generation detector runtime, this joint analysis will constrain the dark energy equation of state with marginalised $1\sigma$ uncertainties of $\sigma(w_0)$~0.005 and $\sigma(w_a)$~0.04. This is comparable to or better than forecasts for future galaxy/intensity mapping surveys, and better constraints are possible when combining these and other future probes with gravitational waves. We find that combining mergers with and without an electromagnetic counterpart helps break parameter degeneracies. Using DeciHz detectors in the post-LISA era, we demonstrate for the first time how merging binaries could achieve a precision on the sum of neutrino masses of $\sigma(\Sigma m_{\nu})$~0.05 eV using $3\times10^6$ sources up to $z=3.5$ with a distance uncertainty of $1\%$, and ~percent or sub-percent precision also on curvature, dark energy, and other parameters, independently from other probes. Finally, we demonstrate how the cosmology dependence in the redshift distribution of mergers can be exploited to improve dark energy constraints if the cosmic merger rate is known, instead of relying on measured distributions as is standard in cosmology. In the coming decades gravitational waves will become a formidable probe of both geometry and large scale structure.

Constraints on Dark Energy from the CSST Galaxy Clusters

We study the potential of the galaxy cluster sample expected from the Chinese Space Station Telescope (CSST) survey to constrain dark energy properties. By modeling the distribution of observed cluster mass for a given true mass to be log-normal and adopting a selection threshold in the observed mass M 200m ≥ 0.836 × 1014 h −1 M ⊙, we find about 4.1 × 105 clusters in the redshift range 0 ≤ z ≤ 1.5 can be detected by the CSST. We construct the Fisher matrix for the cluster number counts from CSST, and forecast constraints on dark energy parameters for models with constant (w 0CDM) and time dependent (w 0 w a CDM) equation of state. In the self-calibration scheme, the dark energy equation of state parameter w 0 of the w 0CDM model can be constrained to Δw 0 = 0.036. If w a is added as a free parameter, we obtain Δw 0 = 0.077 and Δw a = 0.39 for the w 0 w a CDM model, with a Figure of Merit for (w 0, w a ) of 68.99. Should we have perfect knowledge of the observable-mass scaling relation (“known SR” scheme), we would obtain Δw 0 = 0.012 for the w 0CDM model, and Δw 0 = 0.062 and Δw a = 0.24 for the w 0 w a CDM model. The dark energy Figure of Merit of (w 0, w a ) increases to 343.25. This indicates again the importance of calibrating the observable-mass scaling relation for optically selected galaxy clusters. By extending the maximum redshift of the clusters from to , the dark energy Figure of Merit for (w 0, w a ) increases to 89.72 (self-calibration scheme) and 610.97 (“known SR” scheme), improved by a factor of ∼1.30 and ∼1.78, respectively. We find that the impact of clusters’ redshift uncertainty on the dark energy constraints is negligible as long as the redshift error of clusters is smaller than 0.01, achievable by CSST. We also find that the bias in logarithm mass must be calibrated to be 0.30 or better to avoid significant dark energy parameter bias.

Cosmology with the EFTofLSS and BOSS: dark energy constraints and a note on priors

We analyse the BOSS DR12 multipoles of the galaxy power spectrum jointly with measurements of the BAO scale for three different models of dark energy. We use recent measurements performed with a windowless estimator, and an independent and fast pipeline based on EFTofLSS modelling implemented via the FAST-PT algorithm to compute the integrals of the redshift-space loop corrections. We accelerate our analysis further by using the bacco linear power spectrum emulator instead of a Boltzmann solver. We perform two sets of analyses: one including 3σ Planck priors on As and ns , and another that is fully CMB-free, i.e., letting the primordial parameters vary freely. The first model we study is ΛCDM, within which we reproduce previous results obtained with the same estimator. We find a low value of the scalar amplitude in the CMB-free case, in agreement with many previous EFT-based full-shape analyses of the BOSS data. We then study wCDM, finding a lower value of the amplitude in the CMB-free run, coupled with a preference for phantom dark energy with w = -1.17+0.12 -0.11, again in broad agreement with previous results. Finally, we investigate the dark scattering model of interacting dark energy, which we label wACDM. In the CMB-free analysis, we find a large degeneracy between the interaction strength A and the amplitude As , hampering measurements of those parameters. On the contrary, in our run with a CMB prior, we are able to constrain the dark energy parameters to be w = -0.972+0.036 -0.029 and A = 3.9+3.2 -3.7, which show a 1σ hint of interacting dark energy. This is the first measurement of this parameter and demonstrates the ability of this model to alleviate the σ 8 tension. Our analysis can be used as a guide for the analysis of any model with scale-independent growth. Finally, we study the dependence of the results on the priors imposed on the nuisance parameters and find these priors to be informative, with their broadening generating shifts in the contours. We argue for an in depth study of this issue, which can affect current and forthcoming analyses of LSS data.

The First Direct Measurement of Gravitational Potential Decay Rate at Cosmological Scales and Improved Dark Energy Constraint

The integrated Sachs–Wolfe (ISW) effect probes the decay rate (DR) of large-scale gravitational potential and therefore provides a unique constraint on dark energy (DE). However, its constraining power is degraded by the ISW measurement, which relies on cross-correlating with the large-scale structure (LSS) and suffers from uncertainties in galaxy bias and matter clustering. In combination with lensing-LSS cross correlation, DR can be isolated in a way free of uncertainties in galaxy bias and matter clustering. We applied this proposal to the combination of the Data Release 8 galaxy catalog of DESI imaging surveys and Planck cosmic microwave background maps. We achieved the first DR measurement, with a total significance of 3.2σ. We verified the measurements at three redshift bins ([0.2, 0.4), [0.4, 0.6), [0.6, 0.8]), with two LSS tracers (the “low-density points” and the conventional galaxy positions). Despite its relatively low signal-to-noise ratio, the addition of DR significantly improves dark energy constraints, over Sloan Digital Sky Survey baryon acoustic oscillation (BAO) data alone or Pantheon supernovae (SNe) compilation alone. For flat wCDM cosmology, the improvement in the precision of Ω m is a factor of 1.8 over BAO and 1.5 over SNe. For the DE equation of state w, the improvement factor is 1.3 over BAO and 1.4 over SNe. These improvements demonstrate DR as a useful cosmological probe, and therefore we advocate its usage in future cosmological analysis.

Cosmology in the non-linear regime: the small scale miracle

Interest is rising in exploiting the full shape information of the galaxy power spectrum, and in pushing analyses to smaller non-linear scales. Here I use the halo model to quantify the information content in the tomographic angular power spectrum of galaxies Cℓgal(iz) for the future high-resolution surveys Euclid and SKA2. I study how this information varies as a function of the scale cut applied, either with angular cut ℓmax or physical cut kmax. For this, I use analytical covariances with the most complete census of non-Gaussian terms, which proves to be critical. I find that the Fisher information on most cosmological and astrophysical parameters shows a striking behaviour. Beyond the perturbative regime, we first get decreasing returns: the information continues to rise but the slope slows down until reaching saturation. The location of this plateau, at k ∼ 2 Mpc−1, is slightly beyond the reach of current modelling methods and depends to some extent on the parameter and redshift bin considered. I explain the origin of this plateau, which is due to non-linear effects both on the power spectrum, and more importantly on non-Gaussian covariance terms. Then, pushing further, we see the information rising again in the highly non-linear regime, with a steep slope. This is the small-scale miracle, for which I give my interpretation and discuss the properties. There are suggestions that it may be possible to disentangle this information from the astrophysical content, and improve dark energy constraints. Finally, more hints are shown that high-order statistics may yield significant improvements over the power spectrum in this regime, with the improvements increasing with kmax.

The physical origin of dark energy constraints from rubin observatory and CMB-S4 lensing tomography

ABSTRACT We seek to clarify the origin of constraints on the dark energy equation of state parameter from CMB lensing tomography, that is the combination of galaxy clustering and the cross-correlation of galaxies with CMB lensing in a number of redshift bins. We focus on the analytic understanding of the origin of the constraints. Dark energy information in these data arises from the influence of three primary relationships: distance as a function of redshift (geometry), the amplitude of the power spectrum as a function of redshift (growth), and the power spectrum as a function of wavenumber (shape). We find that the effects from geometry and growth play a significant role and partially cancel each other out, while the shape effect is unimportant. We also show that Dark Energy Task Force figure of merit forecasts from the combination of LSST galaxies and CMB-S4 lensing are comparable to the forecasts from cosmic shear in the absence of the CMB lensing map, thus providing an important independent check. Compared to the forecasts with the LSST galaxies alone, combining CMB lensing and LSST clustering information increases the FoM by roughly a factor of 3–4 in the optimistic scenario where systematics are fully under control. We caution that achieving these forecasts will likely require a full analysis of higher-order biasing, photometric redshift uncertainties, and stringent control of other systematic limitations, which are outside the scope of this work, whose primary purpose is to elucidate the physical origin of the constraints.

Linear bias and halo occupation distribution of emission-line galaxies from Nancy Grace Roman Space Telescope

ABSTRACT We present measurements of the linear galaxy bias of Hα and [O iii] emission-line galaxies (ELGs) for the High Latitude Spectroscopic Survey (HLSS) of Nancy Grace Roman Space Telescope (or Roman), using galaxy mocks constructed using semi-analytical model for galaxy formation, Galacticus, with a large cosmic volume and redshift coverage. We compute the two-point statistics of galaxies in configuration space and measure linear bias within scales of 10–50 h−1 Mpc. We adopt different selection algorithms to investigate the impact of the Roman line flux cut, as well as the effect of dust model used to calibrate Galacticus, on the bias measurements. We consider galaxies with Hα and [O iii] emissions over the redshift range 1 < z < 3, as specified by the current baseline for the Roman HLSS. We find that the linear bias for the Hα and [O iii] ELGs can be expressed as a linear function with respect to redshift: b ≃ 0.9z + 0.5 for H$\alpha \, (1\lt z\lt 2)$, and b ≃ z + 0.5 for [O iii] (2 < z < 3). We have also measured the halo occupation distributions of these Hα and [O iii] ELGs to understand their distribution within dark matter haloes. Our results provide key input to enable the reliable forecast of dark energy and cosmology constraints from Roman.

Specific Effect of Peculiar Velocities on Dark-energy Constraints from Type Ia Supernovae

Abstract Peculiar velocities of Type Ia supernova (SN Ia) host galaxies affect the dark-energy parameter constraints in a small but very specific way: the parameters are biased in a single direction in parameter space that is a priori knowable for a given SN Ia data set. We demonstrate the latter fact with a combination of inference from a cosmological N-body simulation with overwhelming statistics applied to the Pantheon SN Ia data set, then confirm it by simple quantitative arguments. We quantify small modifications to the current analyses that would ensure that the effect of cosmological parameters is essentially guaranteed to be negligible.

Dark matter density distributions and dark energy constraints on structure formation including MOND

In recent papers, it was shown explicitly that the sizes of gravitationally bound large-scale cosmic structures can be constrained from the requirement that their gravitational binding self-energy density should at least be equal to the background repulsive dark energy density (for them to be bound). Here, we extend this model to incorporate various dark matter density distributions in the galaxy which are consistent with observation. We also show that the constraints set using modified Newtonian dynamics (MOND) is again consistent with observations and the same as that in the Newtonian case, hence making it impossible to distinguish between the two as also pointed out recently. We also point out that the recent observations of baryon-dominated disk galaxies formed about ten billion years ago indicate the consistency of MOND with observations.

Early dark energy constraints on growing neutrino quintessence cosmologies

We investigate cosmological models in which dynamical dark energy consists of a scalar field whose present-day value is controlled by a coupling to the neutrino sector. The behaviour of the scalar field depends on three functions: a kinetic function, the scalar field potential, and the scalar field-neutrino coupling function. We present an analytic treatment of the background evolution during radiation- and matter-domination for exponential and inverse power law potentials, and find a relaxation of constraints compared to previous work on the amount of early dark energy in the exponential case. We then carry out a numerical analysis of the background cosmology for both types of potential and various illustrative choices of the kinetic and coupling functions. By applying bounds from Planck on the amount of early dark energy, we are able to constrain the magnitude of the kinetic function at early times.

Neutrino mass and dark energy constraints from redshift-space distortions

Cosmology in the near future promises a measurement of the sum of neutrino masses ∑ mν, a fundamental Standard Model parameter, as well as substantially-improved constraints on the dark energy. We use the shape of the BOSS redshift-space galaxy power spectrum, in combination with CMB and supernova data, to constrain the neutrino masses and the dark energy. Essential to this calculation are several recent advances in non-linear cosmological perturbation theory, including fast Fourier transform methods, redshift space distortions, and scale-dependent growth. Our 95% confidence upper bound ∑ mν < 180 meV degrades substantially to ∑ mν < 540 meV when the dark energy equation of state and its first derivative are also allowed to vary, representing a significant challenge to current constraints. We also study the impact of additional galaxy bias parameters, finding that a greater allowed range of scale-dependent bias only slightly shifts the preferred ∑ mν, weakens its upper bound by ≈ 20%, and has a negligible effect on the other cosmological parameters.

Dark Energy Constraints from a five-dimensional AdS Black Hole via AdS/CFT

There are many dark energy models having been investigated with constraint from observational data. The best dark energy candidate is ΛCDM model. In this work, our model has extended to include AdS/CFT correspondent, where the AdS black hole boundary exhibit the FLRW metric foliated with four-dimensional gravity theory, can lead to a modified Friedmann Equation contains extra parameter coming from 5D AdS (hairy) black hole, where such extension to ACDM can be considered. We obtained modified Friedmann equation from both 5D hairless and scalar hair black hole. The effect from extra dimension in hairless black hole solutions can be observed in the form of radiation. Also, it is interesting to see a non-trivial term emerges in scalar hair solution case. However in this study, we only consider Hairless black hole case for data constraint by using a join analysis of Supernovae, CMB and H0 measurement to obtain $ \chi _{\min }^2 $ . As a result, we compare this particular case with ACDM using AIC and BIC statistics.

Effects of completeness and purity on cluster dark energy constraints

The statistical properties of galaxy clusters can only be used for cosmological purposes if observational effects related to cluster detection are accurately characterized. These effects include the selection function associated to cluster finder algorithms and survey strategy. The importance of the selection becomes apparent when different cluster finders are applied to the same galaxy catalog, producing different cluster samples. We consider parametrized functional forms for the observable-mass relation, its scatter as well as the completeness and purity of cluster samples, and study how prior knowledge on these function parameters affects dark energy constraints derived from cluster statistics. Under the assumption that completeness and purity reach 50 % at masses around 10^{13.5} Msun/h, we find that self-calibration of selection parameters in current and upcoming cluster surveys is possible, while still allowing for competitive dark energy constraints. We consider a fiducial survey with specifications similar to those of the Dark Energy Survey (DES) with 5000 deg^2, maximum redshift of zmax ~ 1.0 and threshold observed mass M_{th} ~ 10^{13.8} Msun/h, such that completeness and purity ~ 60 % - 80 % at masses around M_{th}. Perfect knowledge of all selection parameters allows for constraining a constant dark energy equation of state to sigma(w)=0.033. Employing a joint fit including self-calibration of the effective selection degrades constraints to sigma(w)=0.046. External calibrations at the level of 1 % in the parameters of the observable-mass relation and completeness/purity functions are necessary to improve the joint constraints to sigma(w)=0.041. In the lack of knowledge of selection parameters, future experiments probing larger areas and greater depths suffer from stronger relative degradations on dark energy constraints compared to current surveys.

The impact of baryons on the sensitivity of dark energy measurements

Baryonic effects on large-scale structure, if not accounted for, can significantly bias dark energy constraints. As the detailed physics of the baryons is not yet well-understood, correcting for baryon effects introduces additional parameters which must be marginalized over, increasing the uncertainties on the inferred cosmological parameters. Forthcoming weak lensing surveys are aiming for percent-level precision on the dark energy equation of state, so the problem must be thoroughly examined. We use a halo model with analytic modifications which capture the impact of adiabatic contraction of baryons and feedback on the matter power spectrum, and generalize the Navarro-Frenk-White profile to account for a possible inner core. A Fisher analysis predicts degradations of 40% in the $w_0$-$w_a$ Figure of Merit for a Euclid-like survey, and up to 80% for other cosmological parameters. We forecast potential inner core constraints of a few $\mathrm{kpc}$, while for a fixed inner core, adiabatic concentration and feedback parameters are constrained to a few percent. We explore the scales where baryons and dark energy contribute most to the Fisher information, finding that probing to increasingly non-linear scales does little to reduce degradation. Including external baryon information improves our forecasts, but limiting degradation to 1% requires strong priors. Adding Planck cosmic microwave background priors improves the Figure of Merit by a factor of 2.7 and almost completely recovers the individual marginalized errors on $w_0$ and $w_a$. We also quantify the calibration of baryon modelling required to reduce biases of dark energy forecasts to acceptable levels for forthcoming lensing surveys.

The effect of inhomogeneities on dark energy constraints

Constraints on models of the late time acceleration of the universe assume the cosmological principle of homogeneity and isotropy on large scales. However, small scale inhomogeneities can alter observational and dynamical relations, affecting the inferred cosmological parameters. For precision constraints on the properties of dark energy, it is important to assess the potential systematic effects arising from these inhomogeneities. In this study, we use the Type Ia supernova magnitude-redshift relation to constrain the inhomogeneities as described by the Dyer-Roeder distance relation and the effect they have on the dark energy equation of state (w), together with priors derived from the most recent results of the measurements of the power spectrum of the Cosmic Microwave Background and Baryon Acoustic Oscillations. We find that the parameter describing the inhomogeneities (η) is weakly correlated with w. The best fit values w = −0.933 ± 0.065 and η = 0.61 ± 0.37 are consistent with homogeneity at < 2 σ level. Assuming homogeneity (η =1), we find w = −0.961 ± 0.055, indicating only a small change in w. For a time-dependent dark energy equation of state, w0 = −0.951 ± 0.112 and wa = 0.059 ± 0.418, to be compared with w0 = −0.983 ± 0.127 and wa = 0.07 ± 0.432 in the homogeneous case, which is also a very small change. We do not obtain constraints on the fraction of dark matter in compact objects, fp, at the 95% C.L. with conservative corrections to the distance formalism. Future supernova surveys will improve the constraints on η, and hence, fp, by a factor of ∼10.

Dark energy constraints on masses and sizes of large scale cosmic structures

The requirement that their gravitational binding self-energy density must at least equal the background repulsive dark energy density for large scale cosmic structures implies a mass-radius relation of M/R^2 ~ 1g/cm^2, as pointed out earlier. This relation seems to hold true for primeval galaxies as well as those at present epoch. This could set constraints on the nature and evolution of dark energy. Besides, we also set constraints on the size of galaxy clusters and superclusters due to the repulsive cosmological dark energy. This could indicate as to why large scale cosmic structures much larger than ~200Mpc are not seen.

Dark energy constraints in light of Pantheon SNe Ia, BAO, cosmic chronometers and CMB polarization and lensing data

To explore whether there is new physics going beyond the standard cosmological model or not, we constrain seven cosmological models by combining the latest and largest Pantheon Type Ia supernovae sample with the data combination of baryonic acoustic oscillations, cosmic microwave background radiation, Planck lensing and cosmic chronometers. We find that a spatially flat universe is preferred in the framework of $\Lambda$CDM cosmology, that the constrained equation of state of dark energy is very consistent with the cosmological constant hypothesis, that there is no evidence of dynamical dark energy, that there is no hint of interaction between dark matter and dark energy in the dark sector of the universe, and that there does not exist the sterile neutrinos in the neutrino sector of the universe. We also give the 95$\%$ limit of the total mass of three active neutrinos $\Sigma m_\nu<0.178$ eV. It is clear that there is no any departure from the standard cosmological model based on current observational datasets.