Forecast and analysis of the cosmological redshift drift (original) (raw)
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arXiv: Cosmology and Nongalactic Astrophysics, 2020
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Testing late-time cosmic acceleration with uncorrelated baryon acoustic oscillation dataset
Astronomy & Astrophysics
Baryon acoustic oscillations (BAO) involve measuring the spatial distribution of galaxies to determine the growth rate of cosmic structures. We derive constraints on cosmological parameters from 17 uncorrelated BAO measurements that were collected from 333 published data points in the effective redshift range 0.106 ≤ z ≤ 2.36. We test the correlation of the subset using a random covariance matrix. The Λ cold dark matter (ΛCDM) model fit yields the cosmological parameters Ωm = 0.261 ± 0.028 and ΩΛ = 0.733 ± 0.021. Combining the BAO data with the Cosmic Chronometers data, the Pantheon type Ia supernova, and the Hubble diagram of gamma-ray bursts and quasars, the Hubble constant yields 69.85 ± 1.27 km s−1 Mpc−1 and the sound horizon distance gives 146.1 ± 2.15 Mpc. Beyond the ΛCDM model we test ΩkCDM and wCDM. The spatial curvature is Ωk = −0.076 ± 0.012 and the dark energy equation of states is w = −0.989 ± 0.049. We perform the Akaike information criteria test to compare the three mo...
Bayesian Evidence for a cosmological constant using new high-redshift supernova data
Monthly Notices of the Royal Astronomical Society, 2007
We carry out a Bayesian model selection analysis of different dark energy parametrizations using the recent luminosity distance data of high redshift supernovae from Riess et al. 2007 and from the new ESSENCE Supernova Survey. Including complementary cosmological datasets, we found substantial evidence (∆ ln(E) ∼ 1) against a time-varying dark energy equation of state parameter, and against phantom dark energy models. We find a small preference for a standard cosmological constant over accelerating non-phantom models where w is constant, but allowed to vary in the range −1 to −0.33.
High redshift cosmography: new results and implication for dark energy
2012
The explanation of the accelerated expansion of the Universe poses one of the most fundamental questions in physics and cosmology today. If the acceleration is driven by some form of dark energy, one can try to constrain the parameters using a cosmographic approach. Our high-redshift analysis allows us to put constraints on the cosmographic expansion up to the fifth order. It is based on the Union2 Type Ia Supernovae (SNIa) data set, the Hubble diagram constructed from some Gamma Ray Bursts luminosity distance indicators, and gaussian priors on the distance from the Baryon Acoustic Oscillations (BAO), and the Hubble constant h (these priors have been included in order to help break the degeneracies among model parameters). To perform our statistical analysis and to explore the probability distributions of the cosmographic parameters we use the Markov Chain Monte Carlo Method (MCMC). We finally investigate implications of our results for the dark energy, in particular, we focus on the parametrization of the dark energy equation of state (EOS). Actually, a possibility to investigate the nature of dark energy lies in measuring the dark energy equation of state, w, and its time (or redshift) dependence at high accuracy. However, since w(z) is not directly accessible to measurement, reconstruction methods are needed to extract it reliably from observations. Here we investigate different models of dark energy, described through several parametrizations of the equation of state, by comparing the cosmographic and the EOS series.
An improved model-independent assessment of the late-time cosmic expansion
Journal of Cosmology and Astroparticle Physics
In the current work, we have implemented an extension of the standard Gaussian Process formalism, namely the Multi-Task Gaussian Process with the ability to perform a joint learning of several cosmological data simultaneously. We have utilised the "low-redshift" expansion rate data from Supernovae Type-Ia (SN), Baryon Acoustic Oscillations (BAO) and Cosmic Chronometers (CC) data in a joint analysis. We have tested several possible models of covariance functions and find very consistent estimates for cosmologically relevant parameters. In the current formalism, we also find provisions for heuristic arguments which allow us to select the best-suited kernel for the reconstruction of expansion rate data. We also utilised our method to account for systematics in CC data and find an estimate of H 0 = 68.52 +0.94+2.51(sys) −0.94 km/s Mpc −1 and a corresponding r d = 145.61 +2.82 −2.82−4.3(sys) Mpc as our primary result. Subsequently, we find constraints on the present deceleration parameter q 0 = −0.52 ± 0.06 and the transition redshift z T = 0.64 +0.12 −0.09. All the estimated cosmological parameters are found to be in good agreement with the standard ΛCDM scenario. Including the local model-independent H 0 estimate to the analysis we find H 0 = 71.40 +0.30+1.65(sys) −0.30 km/s Mpc −1 and the corresponding r d = 141.29 +1.31 −1.31−2.63(sys) Mpc. Also, the constraints on r d H 0 remain consistent throughout our analysis and also with the model-dependent CMB estimate. Using the Om(z) diagnostic, we find that the concordance model is very consistent within the redshift range z 2 and mildly discrepant for z 2.
Weighing Cosmological Models with SNe Ia and Gamma Ray Burst Redshift Data
Universe, 2019
Many models have been proposed to explain the intergalactic redshift using different observational data and different criteria for the goodness-of-fit of a model to the data. The purpose of this paper is to examine several suggested models using the same supernovae Ia data and gamma-ray burst (GRB) data with the same goodness-of-fit criterion and weigh them against the standard Lambda cold dark matter model (ΛCDM). We have used the redshift—distance modulus (z − μ) data for 580 supernovae Ia with 0.015 ≤ z ≤ 1.414 to determine the parameters for each model and then use these model parameter to see how each model fits the sole SNe Ia data at z = 1.914 and the GRB data up to z = 8.1. For the goodness-of-fit criterion, we have used the chi-square probability determined from the weighted least square sum through non-linear regression fit to the data relative to the values predicted by each model. We find that the standard ΛCDM model gives the highest chi-square probability in all cases ...
Cosmography and cosmic acceleration
Monthly Notices of the Royal Astronomical Society, 2011
We investigate the prospects for determining the accelerating history of the Universe from upcoming measurements of the expansion rate H(z). In our analyses, we use Monte Carlo simulations based on wCDM models to generate samples with different characteristics and calculate the evolution of the deceleration parameter q(z). We show that a cosmographic (and, therefore, model-independent) evidence for cosmic acceleration (q(z < zt) < 0, where zt is the transition redshift) will only be possible with an accuracy in H(z) data greater than the expected in current planned surveys. A brief discussion about the prospects for reconstructing the dark energy equation of state from the parameters H(z) and q(z) is also included.
Observational evidence from supernovae for an accelerating universe and a cosmological constant
The Astronomical …, 2007
We present spectral and photometric observations of 10 type Ia supernovae (SNe Ia) in the redshift range 0.16 ≤ z ≤ 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-Z Supernova Search Team (Garnavich et al. 1998;, this expanded set of 16 high-redshift supernovae and a set of 34 nearby supernovae are used to place constraints on the following cosmological parameters: the Hubble constant (H 0 ), the mass density (Ω M ), the cosmological constant (i.e., the vacuum energy density, Ω Λ ), the deceleration parameter (q 0 ), and the dynamical age of the Universe (t 0 ). The distances of the high-redshift SNe Ia are, on average, 10% to 15% farther than expected in a low mass density (Ω M = 0.2) Universe without a cosmological constant. Different light curve fitting methods, SN Ia subsamples, and prior constraints unanimously favor eternally expanding models with positive cosmological constant (i.e., Ω Λ > 0) and a current acceleration of the expansion (i.e., q 0 < 0). With no prior constraint on mass density other than Ω M ≥ 0, the spectroscopically confirmed SNe Ia are statistically consistent with q 0 < 0 at the 2.8σ -2and 3.9σ confidence levels, and with Ω Λ > 0 at the 3.0σ and 4.0σ confidence levels, for two different fitting methods respectively. Fixing a "minimal" mass density, Ω M = 0.2, results in the weakest detection, Ω Λ > 0 at the 3.0σ confidence level from one of the two methods. For a flat-Universe prior (Ω M + Ω Λ = 1), the spectroscopically confirmed SNe Ia require Ω Λ > 0 at 7σ and 9σ formal significance for the two different fitting methods. A Universe closed by ordinary matter (i.e., Ω M = 1) is formally ruled out at the 7σ to 8σ confidence level for the two different fitting methods. We estimate the dynamical age of the Universe to be 14.2 ±1.5 Gyr including systematic uncertainties in the current Cepheid distance scale. We estimate the likely effect of several sources of systematic error, including progenitor and metallicity evolution, extinction, sample selection bias, local perturbations in the expansion rate, gravitational lensing, and sample contamination. Presently, none of these effects reconciles the data with Ω Λ = 0 and q 0 ≥ 0. subject headings: supernovae:general ; cosmology:observations Application of large-format CCDs and sophisticated image analysis techniques by the Supernova Cosmology Project led to the discovery of SN 1992bi (z = 0.46) followed by 6 more SNe Ia at z ≈ 0.4 . Employing a correction for the luminosity/light-curve shape relation (but none for host galaxy extinction), comparison of these SNe Ia to the Calán/Tololo sample gave an initial indication of "low" Ω Λ and "high" Ω M : Ω Λ = 0.06 +0.28 −0.34 for a flat Universe and Ω M = 0.88 +0.69 −0.60
Sensitivity of Redshift Distortion Measurements to Cosmological Parameters
The Astrophysical Journal, 1998
The multipole moments of the power spectrum of large scale structure, observed in redshift space, are calculated for a finite sample volume including the effects of both the linear velocity field and geometry. A variance calculation is also performed including the effects of shot noise. The sensitivity with which a survey with the depth and geometry of the Sloan Digital Sky Survey (SDSS) can measure cosmological parameters Ω 0 and b 0 (the bias) or λ 0 (the cosmological constant) and b 0 is derived through fitting power spectrum moments to the large scale structure in the linear regime in a way which is independent of the evolution of the galaxy number density. A fiducial model is assumed and the region of parameter space which can then be excluded to a given confidence limit is determined. In the absence of geometric and evolutionary effects, the ratios of multipole moments (in particular the zeroth and second), are degenerate for models of constant β ≈ Ω 0.6 /b 0. However, this degeneracy is broken by the Hubble expansion, so that in principle Ω 0 and b 0 may be measured separately by a deep enough galaxy redshift survey (Nakamura, Matsubara, & Suto (1997)). We find that for surveys of the approximate depth of the SDSS no restrictions can be placed on Ω 0 at the 99% confidence limit when a fiducial open, Ω 0 = 0.3 model is assumed and bias is unconstrained. At the 95% limit, Ω 0 < .85 is ruled out. Furthermore, for this fiducial model, both flat (cosmological constant) and open models are expected to reasonably fit the data. For flat, cosmological constant models with a fiducial Ω 0 = 0.3, we find that models with Ω 0 > 0.48 are ruled out at the 95% confidence limit regardless of the choice of the bias parameter, and open models cannot fit the data even at the 99% confidence limit. We also find significant deviations in β from the naive estimate for both fiducial models. Thus, we conclude for the SDSS that linear evolution-free statistics alone can strongly distinguish between Ω 0 = 1 and low matter density models only in the case of the fiducial cosmological constant model. For the open model, Ω 0 = 1 is only at best only nominally excluded unless Ω 0 < 0.3.
The time evolution of cosmological redshift as a test of dark energy
Monthly Notices of the Royal Astronomical Society, 2007
The variation of the expansion rate of the Universe with time produces an evolution in the cosmological redshift of distant sources (for example quasar Lyman-α absorption lines), that might be directly observed by future ultra stable, high-resolution spectrographs (such as CODEX) coupled to extremely large telescopes (such as European Southern Observatory's Extremely Large Telescope, ELT). This would open a new window to explore the physical mechanism responsible for the current acceleration of the Universe. We investigate the evolution of cosmological redshift from a variety of dark energy models, and compare it with simulated data. We perform a Fisher matrix analysis and discuss the prospects for constraining the parameters of these models and for discriminating among competing candidates. We find that, because of parameter degeneracies, and of the inherent technical difficulties involved in this kind of observations, the uncertainties on parameter reconstruction can be rather large unless strong external priors are assumed. However, the method could be a valuable complementary cosmological tool, and give important insights on the dynamics of dark energy, not obtainable using other probes.