Baryon Acoustic Oscillation Measurements Research Articles

Robust preference for Dynamical Dark Energy in DESI BAO and SN measurements

Recent Baryon Acoustic Oscillation (BAO) measurements released by DESI, when combined with Cosmic Microwave Background (CMB) data from Planck and two different samples of Type Ia supernovae (Pantheon-Plus and DESY5) reveal a preference for Dynamical Dark Energy (DDE) characterized by a present-day quintessence-like equation of state that crossed into the phantom regime in the past. A core ansatz for this result is assuming a linear Chevallier-Polarski-Linder (CPL) parameterization w(a) = w 0 + wa (1-a) to describe the evolution of the DE equation of state (EoS). In this paper, we test if and to what extent this assumption impacts the results. To prevent broadening uncertainties in cosmological parameter inference and facilitate direct comparison with the baseline CPL case, we focus on 4 alternative well-known models that, just like CPL, consist of only two free parameters: the present-day DE EoS (w0 ) and a parameter quantifying its dynamical evolution (wa ). We demonstrate that the preference for DDE remains robust regardless of the parameterization: w0 consistently remains in the quintessence regime, while wa consistently indicates a preference for a dynamical evolution towards the phantom regime. This tendency is significantly strengthened by DESY5 SN measurements. By comparing the best-fit χ2 obtained within each DDE model, we notice that the linear CPL parameterization is not the best-fitting case. Among the models considered, the EoS proposed by Barboza and Alcaniz consistently leads to the most significant improvement.

DESI dark energy time evolution is recovered by cosmologically coupled black holes

Recent baryon acoustic oscillation (BAO) measurements by the Dark Energy Spectroscopic Instrument (DESI) provide evidence that dark energy (DE) evolves with time, as parameterized by a w 0 w a equation of state. Cosmologically coupled black holes (BHs) provide a DE source that naturally evolves with time, because BH production tracks cosmic star-formation. Using DESI BAO measurements and priors informed by Big Bang Nucleosynthesis, we measure the fraction of baryonic density converted into BHs, assuming that all DE is sourced by BH production. We find that the best-fit DE density tracks each DESI best-fit w 0 w a model within 1σ, except at redshifts z ≲ 0.2, highlighting limitations of the w 0 w a parameterization. Cosmologically coupled BHs produce H 0 = (69.94 ± 0.81) km s-1 Mpc-1, with the same χ 2 as ΛCDM, and with two fewer parameters than w 0 w a . This value reduces tension with SH0ES to 2.7σ and is in excellent agreement with recent measurements from the Chicago-Carnegie Hubble Program. Because cosmologically coupled BH production depletes the baryon density established by primordial nucleosynthesis, these BHs provide a physical explanation for the “missing baryon problem” and the anomalously low sum of neutrino masses preferred by DESI.The global evolution of DE is an orthogonal probe of cosmological coupling, complementing constraints on BH mass-growth from elliptical galaxies, stellar binaries, globular clusters, the LIGO-Virgo-KAGRA merging population, and X-ray binaries.A DE density that correlates with cosmic star-formation: 1) is a natural outcome of cosmological coupling in BH populations; 2) eases tension between early and late-time cosmological probes; and 3) produces time-evolution toward a late-time ΛCDM cosmology different from Cosmic Microwave Background projections.

Phenomenological emergent dark energy in the light of DESI Data Release 1

This manuscript revisits the phenomenological emergent dark energy model (PEDE) by confronting it with recent cosmological data from early and late times. In particular we analyze PEDE model by using the baryon acoustic oscillation (BAO) measurements coming from both Dark Energy Spectroscopy Instrument (DESI) data release 1 and Sloan Digital Sky Survey (SDSS). Additionally, the measurements from cosmic chronometers, supernovae type Ia (Pantheon+), quasars, hydrogen II galaxies and cosmic background radiation distance priors are considered. By performing a Bayesian analysis based on Monte Carlo Markov Chain, we find consistent results on the constraints when SDSS and DESI are considered. However, we find higher values on the Hubble constant than Supernova H0 for the Equation of State (SH0ES) does although it is still in agreement, within 1σ confidence level, when BAO measurements are added. Furthermore, we estimate the age of the Universe younger ∼3% than the one predicted by the standard cosmology. Additionally, we report values of q0=−0.771−0.007+0.007, zT=0.764−0.011+0.011 for the deceleration parameter today and the deceleration–acceleration transition redshift, respectively. However, PEDE cosmology is disfavored by the combined samples.

Prospect of Precision Cosmology and Testing General Relativity using Binary Black Holes- Galaxies Cross-correlation

Abstract Modified theories of gravity predict deviations from General Relativity (GR) in the propagation of gravitational waves (GW) across cosmological distances. A key prediction is that the GW luminosity distance will vary with redshift, differing from the electromagnetic (EM) luminosity distance due to varying effective Planck mass. We introduce a model-independent, data-driven approach to explore these deviations using multi-messenger observations of dark standard sirens (Binary Black Holes, BBH). By combining GW luminosity distance measurements from dark sirens with Baryon Acoustic Oscillation (BAO) measurements, BBH redshifts inferred from cross-correlation with spectroscopic or photometric galaxy surveys, and sound horizon measurements from the Cosmic Microwave Background (CMB), we can make a data-driven test of GR (jointly with the Hubble constant) as a function of redshift. Using the multi-messenger technique with the spectroscopic DESI galaxy survey, we achieve precise measurements of deviations in the effective Planck mass variation with redshift. For the Cosmic Explorer and Einstein Telescope (CEET), the best precision is approximately 3.6%, and for LIGO-Virgo-KAGRA (LVK), it is 7.4% at a redshift of $\rm {z = 0.425}$. Additionally, we can measure the Hubble constant with a precision of about 1.1% from CEET and 7% from LVK over five years of observation with a 75% duty cycle. We also explore the potential of cross-correlation with photometric galaxy surveys from the Rubin Observatory, extending measurements up to a redshift of $\rm {z \sim 2.5}$. This approach can reveal potential deviations from models affecting GW propagation using numerous dark standard sirens in synergy with DESI and the Rubin Observatory.

Early and late observational tension: dark energy parametrizations in horava-lifshitz gravity via baryon acoustic oscillations

We investigate late-time cosmic expansion within the Horava Lifshitz gravity framework using Barboza Alcaniz (BA) and Jassal Bagla Padmanabhan Parametrizations (JBP) as alternatives to general relativity. Anisotropic scaling is introduced at ultraviolet scales. Our aim is to constrain each cosmological parameter using the crucial Baryon Acoustic Oscillation (BAO) scale, specifically the sound horizon (r d ), by treating (r d ) as a free parameter. We employ 30 Hubble parameter measurements (H(z)) from cosmic chronometers, along with Type Ia Supernovae, Gamma-Ray Bursts, Quasars, and 24 uncorrelated BAO measurements spanning z = 0.106 to z = 2.33. The analysis includes the 2022 Hubble constant measurement by Riess (R22) as an additional prior and aims to minimize errors by simulating random correlations in the covariance matrix. In both the BA and JBP frameworks, utilizing the full dataset yields sound horizon results of r d = 146.5399 ± 2.4519 Mpc and r d = 146.4533 ± 2.4519 Mpc, respectively. When incorporating R22 results, the sound horizon values become r d = 143.4721 ± 1.8324 Mpc and r d = 142.9826 ± 1.9084 Mpc. These findings reveal a discrepancy between early and late observations, echoing the H 0 tension. Notably, excluding R22 aligns r d with Planck and SDSS results. Model predictions are evaluated against Hubble Measurements and the ΛCDM Paradigm. A comparative study between BA and JBP Models using the Cosmography test shows both models fitting seamlessly within the phantom region. Statistical analysis suggests neither model can be ruled out based on the latest observational measurements.

Late time cosmic acceleration through parametrization of Hubble parameter in [formula omitted] gravity

This paper explores the rapid expansion of the Universe during its later stages within the context of f(R,Lm) gravity theory. We present a novel parametrization of the Hubble parameter in a manner independent of any specific model and employ it to analyze the Friedmann equations within the FLRW Universe framework. Using a Markov Chain Monte Carlo (MCMC) approach, we derive the model parameters by analyzing a composite dataset comprising 31 Cosmic Chronometers (CC) data points, 26 independent Baryonic Acoustic Oscillations (BAO) measurements, and 1701 data points from Pantheon+SH0ES dataset. The trajectory of the deceleration parameter highlights the shift from deceleration to acceleration in the evolution of the Universe. Additionally, we delve into the dynamics of fundamental cosmological variables for two nonlinear f(R,Lm) models, including energy density, pressure, equation of state (EoS) parameter, and energy conditions.

Baryon Acoustic Oscillation Theory and Modelling Systematics for the DESI 2024 results

Abstract This paper provides a comprehensive overview of how fitting of Baryon Acoustic Oscillations (BAO) is carried out within the upcoming Dark Energy Spectroscopic Instrument’s (DESI) 2024 results using its DR1 dataset, and the associated systematic error budget from theory and modelling of the BAO. We derive new results showing how non-linearities in the clustering of galaxies can cause potential biases in measurements of the isotropic (αiso) and anisotropic (αap) BAO distance scales, and how these can be effectively removed with an appropriate choice of reconstruction algorithm. We then demonstrate how theory leads to a clear choice for how to model the BAO and develop, implement and validate a new model for the remaining smooth-broadband (i.e., without BAO) component of the galaxy clustering. Finally, we explore the impact of all remaining modelling choices on the BAO constraints from DESI using a suite of high-precision simulations, arriving at a set of best-practices for DESI BAO fits, and an associated theory and modelling systematic error. Overall, our results demonstrate the remarkable robustness of the BAO to all our modelling choices and motivate a combined theory and modelling systematic error contribution to the post-reconstruction DESI BAO measurements of no more than 0.1% (0.2%) for its isotropic (anisotropic) distance measurements. We expect the theory and best-practices laid out to here to be applicable to other BAO experiments in the era of DESI and beyond.

The Negative Baryon Acoustic Oscillation Shift in the Lyα Forest from Cosmological Simulations

We present the first measurement of the Lyα forest baryon acoustic oscillations (BAO) shift parameter from cosmological simulations. In particular, we generate a suite of 1000 accurate effective field-level bias-based Lyα forest simulations of volume V=(1h−1Gpc)3 at z = 2, both in real and redshift space, calibrated upon two fixed-and-paired cosmological hydrodynamic simulations. To measure the BAO, we stack the 3D power spectra of the 1000 different realizations, compute the average, and use a model accounting for a proper smooth-peak component decomposition of the power spectrum, to fit it via an efficient Markov Chain Monte Carlo scheme estimating the covariance matrices directly from the simulations. We report the BAO shift parameters to be α=0.9969−0.0014+0.0014 and α=0.9905−0.0027+0.0027 in real and redshift space, respectively. We also measure the bias b lya and the BAO broadening parameter Σnl, finding blya=−0.1786−0.0001+0.0001 and Σnl=3.87−0.20+0.20 in real space, and blya=−0.073−0.004+0.005 and Σnl=6.55−0.22+0.23 in redshift space. Moreover, we measure the linear Kaiser factor βlya=1.39−0.18+0.24 from the isotropic redshift space fit. Overall, we find evidence for a negative shift of the BAO peak at the ∼2.2σ and ∼3.5σ levels in real and redshift space, respectively. This work sets new important theoretical constraints on the Lyα forest BAO scale and offers a potential solution to the tension emerging from previous observational analysis, in light of ongoing and upcoming Lyα forest spectroscopic surveys, such as DESI, the Prime Focus Spectrograph Survey, and WEAVE-QSO.

Gravitational lensing of dark energy models and ΛCDM using observational data in loop quantum cosmology

This paper investigates the accelerated cosmic expansion in the late Universe by examining two dark energy models, viscous modified Chaplygin gas (VsMCG) and variable modified Chaplygin gas (VMCG), within loop quantum cosmology alongside the ΛCDM model. The objective is to constrain cosmic parameters using the ΛCDM model and 30 of the latest H(z) measurements from cosmic chronometers (CC), including Type Ia Supernovae, Gamma-Ray Bursts (GRB), Quasars, and 24 uncorrelated baryon acoustic oscillations (BAO) measurements across a redshift range from 0.106 to 2.33. The latest Hubble constant measurement from Riess in 2022 is included to enhance constraints. In the ΛCDM, VsMCG, and VMCG frameworks, best-fit parameters for the Hubble parameter (H0) and sound horizon (rd) are obtained. The results highlight significant disparities between H0 and rd values from late-time observational measurements, reflecting the known H0 and rd tensions. The gravitational lensing optical depth of the two dark energy models is studied by plotting log⁡(τ(zl)/H0−3τN) vs zl. The probability of finding gravitational lenses (optical depth) in both models increases with lens redshift zl. The change in optical depth behavior for different parameter constraints is graphically analyzed. A joint analysis of VsMCG and VMCG with ΛCDM is conducted. While the models diverge in the early Universe, they are indistinguishable at low redshift. Using the Akaike information criteria, the analysis indicates that neither dark energy model can be dismissed based on the latest observations.

Constraints on the parameters of modified Chaplygin–Jacobi and modified Chaplygin–Abel gases in f(T) gravity

In this work, we explore the parameter constraints of two dark energy models, namely the Modified Chaplygin–Jacobi gas (MCJG) and Modified Chaplygin–Abel gas (MCAG), within the context of [Formula: see text] gravity model in a non-flat Friedmann–Lemaître–Robertson–Walker (FLRW) universe. Our investigation involves comparing the equation of state for the MCJG and MCAG dark energy models with the equation of state derived from the [Formula: see text] gravity model. To derive constraints for the dark energy and [Formula: see text] gravity models, we use recent astronomical datasets, including [Formula: see text] data, type Ia supernovae observations, Gamma Ray Bursts data, quasar data, and Baryon Acoustic Oscillation (BAO) measurements. We present the reduced Hubble parameter in terms of observable parameters such as [Formula: see text] (density parameter of radiation), [Formula: see text] (density parameter of dark matter), [Formula: see text] (density parameter associated with spatial curvature), [Formula: see text] (density parameter of Modified Chaplygin–Jacobi gas), [Formula: see text] (density parameter of Modified Chaplygin–Abel gas), and [Formula: see text] (present value of the Hubble parameter). We explore the cosmological evolution through various cosmic diagnostic parameters, including the deceleration parameter, [Formula: see text] diagnostic, and statefinder diagnostic pair [Formula: see text]. These diagnostic parameters offer valuable insights into the expansion dynamics and the nature of dark energy in the universe. We have also assessed the viability of the models using the information criteria. Our aim is to shed light on the nature of dark energy and its connection to the [Formula: see text] gravity model, and ultimately gain a deeper understanding of the underlying mechanisms driving the accelerated expansion of our universe.

Testing the cosmic distance duality relation with Type Ia supernova and transverse BAO measurements

In this work, we test the cosmic distance duality relation (CDDR) by comparing the angular diameter distance (ADD) derived from the transverse Baryon Acoustic Oscillations (BAO) data with the luminosity distance (LD) from the Pantheon type Ia supernova (SNIa) sample. The binning method and Gaussian process are employed to match ADD data with LD data at the same redshift. First, we use nonparametric and parametric methods to investigate the impact of the specific prior values of the absolute magnitude MB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_\ extrm{B}$$\\end{document} from SNIa observations and the sound horizon scale rs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$r_\ extrm{s}$$\\end{document} from transverse BAO measurements on the CDDR tests. The results obtained from the parametric and non-parametric methods indicate that specific prior values of MB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_\ extrm{B}$$\\end{document} and rs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$r_\ extrm{s}$$\\end{document} lead to significant biases on the CDDR test. Then, to avoid these biases, we propose a method independent of MB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_\ extrm{B}$$\\end{document} and rs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$r_\ extrm{s}$$\\end{document} to test CDDR by considering the fiducial value of κ≡10MB5rs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\kappa \\equiv 10^{M_\ extrm{B} \\over 5}r_\ extrm{s}$$\\end{document} as a nuisance parameter and then marginalizing its influence with a flat prior in the analysis. No violation of the CDDR is found, and the transverse BAO measurement can be used as a powerful tool to verify the validity of CDDR in the cosmological-model-independent method.

Constraining holographic dark energy and analyzing cosmological tensions

We investigate cosmological constraints on the holographic dark energy (HDE) using the state-of-the-art cosmological datasets: Planck CMB angular power spectra and weak lensing power spectra, Atacama Cosmology Telescope (ACT) temperature power spectra, baryon acoustic oscillation (BAO) and redshift-space distortion (RSD) measurements from six-degree-field galaxy survey and Sloan Digital Sky Survey (DR12 & DR16) and the Cepheids-Supernovae measurement from SH0ES team (R22). We also examine the HDE model and ΛCDM with and without Neff (effective number of relativistic species) being treated as a free parameter. We find that the HDE model can relieve the tensions of H0 and S8 to certain degrees. With “Planck+ACT+BAO+RSD” datasets, the constraints are H0=69.70±1.39km s−1Mpc−1 and S8=0.823±0.011 in HDE model, which brings down the Hubble tension down to 1.92σ confidence level (C.L.) and the S8 tension to (1−2)σ C.L. By adding the R22 data, their values are improved as H0=71.86±0.93km s−1Mpc−1 and S8=0.813±0.010, which further brings the Hubble tension down to 0.85σ C.L. and relieves the S8 tension. We also quantify the goodness-of-fit of different models with Akaike information criterion (AIC) and Bayesian information criterion (BIC), and find that the HDE agrees with the observational data better than the ΛCDM and other extended models (treating Neff as free for fitting).

Investigating early dark energy with new observations

This paper mainly presents updated constraints on several types of early dark energy (EDE) models proposed by V. Pettorino et al. using observations of cosmic microwave background radiation (CMB) from Planck satellite, the Pantheon Type Ia supernovae (SNIa) sample, and baryon acoustic oscillation (BAO) measurements. The results yield stringent upper limits on the constant EDE fraction parameter Ωe. While the present equation of state (EoS) of dark energy w0 in the EDE1 model suggests a mild tendency towards a value less than −1, these models remain compatible with the ΛCDM scenario. Partly as a result of this slight tendency towards phantom late-time physics, EDE1 model supports a higher Hubble constant value, potentially narrowing the Hubble tension gap. The global fitting results also align with the notion that the constraint ability on Ωe weakens when dark energy is present only over a limited period after last scattering. Furthermore, by using the formalism of Fisher information matrix, we forecast uncertainties in the measured parameters of EDE models from the next-generation “Stage 4” CMB (CMB-S4) experiment. Forecasted precision of w0 and Ωe surpasses certain prior works, and most other basic parameters exhibit significantly higher limit precision compared to Planck 2018 results within the ΛCDM framework. To confirm the presence of EDE within the EDE1∼EDE4 parameterization frameworks, further advancements in observations are crucial.

Cosmological measurements from the CMB and BAO are insensitive to the tail probability in the assumed likelihood

When fitting cosmological models to data, a Bayesian framework is commonly used, requiring assumptions on the form of the likelihood and model prior. In light of current tensions between different data, it is interesting to investigate the robustness of cosmological measurements to statistical assumptions about the likelihood distribution from which the data was drawn. We consider the impact of changes to the likelihood caused by uncertainties due to the finite number of mock catalogs used to estimate the covariance matrix, leading to the replacement of the standard Gaussian likelihood with a multivariate t-distribution. These changes to the likelihood have a negligible impact on recent cosmic microwave background (CMB) lensing and baryon acoustic oscillation (BAO) measurements, for which covariance matrices were measured from mock catalogs. We then extend our analysis to perform a sensitivity test on the Gaussian likelihoods typically adopted, considering how increasing the size of the tails of the likelihood (again using a t-distribution) affects cosmological inferences. For an open ΛCDM model constrained by BAO alone, we find that increasing the weight in the tails shifts and broadens the resulting posterior on the parameters, with a ∼0.2–0.4σ effect on ΩΛ and Ωk. In contrast, the CMB temperature and polarization constraints in ΛCDM showed less than 0.03σ changes in the parameters, except for {τ, ln(1010 A s), σ 8, S 8, σ 8Ω0.25 m, z re, 109 A s e -2τ } which shifted by around 0.1–0.2σ. If we use solely ℓ < 30 data, the amplitude A s e -2τ varies in the posterior mean by 0.7σ and the error bars increase by 6%. We conclude, at least for current-generation CMB and BAO measurements, that uncertainties in the shape and tails of the likelihood do not contribute to current tensions.

Some classes of interacting two-fluid model of the expanding universe

We consider interacting dark matter-dark energy models arising out of a general interaction term Q=f(ρm,ρd,ρ̇m,ρ̇d). Here f is a functional relation connecting the energy densities ρ m and ρ d and their derivatives w.r.t. time t. In our model we consider two interacting barotropic fluid with constant equation of state ω m and ω d . By considering a dynamical interaction between them we trace out the cosmological evolution dynamics of the Universe. We analytically solve the model by considering a constant ratio between the two fluids and then track the corresponding analytical results using observational data from the baryon acoustic oscillation measurements, Type Ia supernovae measurements and the local Hubble constant measurements. From this general setting we introduce three different models and nine different interaction function. Our final aim is to set up a comparative analysis of the various class of models under the different interaction function using common theoretical and numerical analysis.

Forecasting the BAO measurements of the CSST galaxy and AGN spectroscopic surveys

ABSTRACT The spectroscopic survey of the China’s Space Survey Telescope (CSST) is expected to obtain a huge number of slitless spectra, including more than one hundred million galaxy spectra and millions of active galactic nuclei (AGNs) spectra. By making use of these spectra, we can measure the Baryon Acoustic Oscillation (BAO) signals over large redshift ranges with excellent precisions. In this work, we predict the CSST measurements of the post-reconstruction galaxy power spectra at $0\lt z\lt 1.2$ and pre-reconstruction AGN power spectra at $0\lt z\lt 4$, and derive the BAO signals at different redshift bins by constraining the BAO scaling parameters using the Markov Chain Monte Carlo method. Our result shows that the CSST spectroscopic survey can provide accurate BAO measurements with precisions higher than 1 and 3 per cent for the galaxy and AGN surveys, respectively. By comparing with current measurements in the same range at low redshifts, this can improve the precisions by a factor of $2\sim 3$, and similar precisions can be obtained in the pessimistic case. We also investigate the constraints on the cosmological parameters using the measured BAO data by the CSST, and obtain stringent constraint results for the energy density of dark matter, Hubble constant, and equation of state of dark energy.

Testing the consistency of early and late cosmological parameters with BAO and CMB data

The recent local measurements of the Hubble constant H0, indicate a significant discrepancy of over 5σ compared to the value inferred from Planck observations of the cosmic microwave background (CMB). In this paper, we try to test the standard cosmological model ΛCDM by testing the consistency of early and late cosmological parameters in the same observed data. In practice, we simultaneously derive the early and late parameters using baryon acoustic oscillation (BAO) measurements, which provide both low and high-redshift information. CMB data are also included in the analysis as a “distance prior”, which tracks the same BAO feature and resolve parameter degeneracy. By using the parameter ωm=Ωmh2, we introduce ratio(ωm), defined as the ratio of ωm which are constrained from high and low-redshift measurements respectively, to quantify the consistency between early and late parameters. We obtained a value of ratio(ωm)=1.0069±0.0070, indicating there is no tension between early parameters and late parameters in the framework of ΛCDM model. As a result, our test does not expose the defects of the ΛCDM model. In addition, we forecast the future BAO measurements of ratio(ωm), using several galaxy redshift surveys and 21 cm intensity mapping surveys, and find that these measurements can significantly improve the precision of cosmological parameters.

21 cm Intensity Mapping with the DSA-2000

Line-intensity mapping is a promising probe of the Universe’s large-scale structure. We explore the sensitivity of the DSA-2000, a forthcoming array consisting of over 2000 dishes, to the statistical power spectrum of neutral hydrogen’s 21 cm emission line. These measurements would reveal the distribution of neutral hydrogen throughout the near-redshift Universe without necessitating resolving individual sources. The success of these measurements relies on the instrument’s sensitivity and resilience to systematics. We show that the DSA-2000 will have the sensitivity needed to detect the 21 cm power spectrum at z ≈ 0.5 and across power spectrum modes of 0.03–35.12 h Mpc−1 with 0.1 h Mpc−1 resolution. We find that supplementing the nominal array design with a dense core of 200 antennas will expand its sensitivity at low power spectrum modes and enable measurement of Baryon Acoustic Oscillations. Finally, we present a qualitative discussion of the DSA-2000's unique resilience to sources of systematic error that can preclude 21 cm intensity mapping.

Emulating Power Spectra for Prereconstructed and Postreconstructed Galaxy Samples

The small-scale linear information in galaxy samples typically lost during nonlinear growth can be restored to a certain level by the density field reconstruction, which has been demonstrated for improving the precision of the baryon acoustic oscillation (BAO) measurements. As proposed in the literature, a joint analysis of the power spectrum before and after the reconstruction enables an efficient extraction of information carried by high-order statistics. However, the statistics of the postreconstruction density field are difficult to model. In this work, we circumvent this issue by developing an accurate emulator for the prereconstructed, postreconstructed, and cross-power spectra ( Ppre , P post, P cross) up to k = 0.5 h Mpc−1 based on the Dark Quest N-body simulations. The accuracy of the emulator is at the percent level; namely, the error of the emulated monopole and quadrupole of the power spectra is less than 1% and 10% of the ground truth, respectively. A fit to an example power spectrum using the emulator shows that the constraints on cosmological parameters get largely improved using Ppre +P post+P cross with kmax=0.25hMpc−1 , compared to that derived from Ppre alone; namely, the constraints on (Ω m , H 0, σ 8) are tightened by ∼41%–55%, and the uncertainties of the derived BAO and RSD parameters (α ⊥, α ∣∣, f σ 8) shrink by ∼28%–54%, respectively. This highlights the complementarity among Ppre , P post, and P cross, which demonstrates the efficiency and practicability of a joint Ppre , P post, and P cross analysis for cosmological implications.

Role of future SNIa data from Rubin LSST in reinvestigating cosmological models

ABSTRACT We study how future Type Ia supernovae (SNIa) standard candles detected by the Vera C. Rubin Observatory (LSST) can constrain some cosmological models. We use a realistic 3-yr SNIa simulated data set generated by the LSST Dark Energy Science Collaboration time domain pipeline, which includes a mix of spectroscopic and photometrically identified candidates. We combine these data with cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements to estimate the dark energy model parameters for two models – the baseline Lambda cold dark matter (ΛCDM) and Chevallier–Polarski–Linder (CPL) dark energy parametrization. We compare them with the current constraints obtained from the joint analysis of the latest real data from the Pantheon SNIa compilation, CMB from Planck 2018 and BAO. Our analysis finds tighter constraints on the model parameters along with a significant reduction of correlation between H0 and σ8,0. We find that LSST is expected to significantly improve upon the existing SNIa data in the critical analysis of cosmological models.