scholarly journals Determining the range of validity of quasar X-ray and UV flux measurements for constraining cosmological model parameters

2021 ◽  
Vol 502 (4) ◽  
pp. 6140-6156 ◽  
Author(s):  
Narayan Khadka ◽  
Bharat Ratra
Keyword(s):  
Cosmological Model ◽  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Model Parameters ◽  
Independent Manner ◽  
Data Set ◽  
X Ray ◽  
Cosmological Constraints ◽  
Flux Measurements ◽  
Model Independent

ABSTRACT We use six different cosmological models to study the recently released compilation of X-ray and UV flux measurements of 2038 quasars (QSOs) which span the redshift range 0.009 ≤ z ≤ 7.5413. We find, for the full QSO data set, that the parameters of the X-ray and UV luminosities LX−LUV relation used to standardize these QSOs depend on the cosmological model used to determine these parameters, i.e. it appears that the full QSO data set includes QSOs that are not standardized and so cannot be used for the purpose of constraining cosmological parameters. Subsets of the QSO data, restricted to redshifts z ≲ 1.5–1.7 obey the LX−LUV relation in a cosmological-model-independent manner, and so can be used to constrain cosmological parameters. The cosmological constraints from these lower z, smaller QSO data subsets are mostly consistent with, but significantly weaker than, those that follow from baryon acoustic oscillation and Hubble parameter measurements.

scholarly journals Using quasar X-ray and UV flux measurements to constrain cosmological model parameters

2020 ◽  
Vol 497 (1) ◽  
pp. 263-278 ◽  
Author(s):  
Narayan Khadka ◽  
Bharat Ratra
Keyword(s):  
Cosmological Parameters ◽  
Hubble Constant ◽  
Acoustic Oscillation ◽  
Joint Analysis ◽  
Model Parameters ◽  
Density Parameter ◽  
Current Standard ◽  
X Ray ◽  
Flux Measurements ◽  
Parameter Constraints

ABSTRACT Risaliti and Lusso have compiled X-ray and UV flux measurements of 1598 quasars (QSOs) in the redshift range 0.036 ≤ z ≤ 5.1003, part of which, z ∼ 2.4 − 5.1, is largely cosmologically unprobed. In this paper we use these QSO measurements, alone and in conjunction with baryon acoustic oscillation (BAO) and Hubble parameter [H(z)] measurements, to constrain cosmological parameters in six different cosmological models, each with two different Hubble constant priors. In most of these models, given the larger uncertainties, the QSO cosmological parameter constraints are mostly consistent with those from the BAO + H(z) data. A somewhat significant exception is the non-relativistic matter density parameter Ωm0 where QSO data favour Ωm0 ∼ 0.5 − 0.6 in most models. As a result, in joint analyses of QSO data with H(z) + BAO data the 1D Ωm0 distributions shift slightly towards larger values. A joint analysis of the QSO + BAO + H(z) data is consistent with the current standard model, spatially-flat ΛCDM, but mildly favours closed spatial hypersurfaces and dynamical dark energy. Since the higher Ωm0 values favoured by QSO data appear to be associated with the z ∼ 2 − 5 part of these data, and conflict somewhat with strong indications for Ωm0 ∼ 0.3 from most z < 2.5 data as well as from the cosmic microwave background anisotropy data at z ∼ 1100, in most models, the larger QSO data Ωm0 is possibly more indicative of an issue with the z ∼ 2 − 5 QSO data than of an inadequacy of the standard flat ΛCDM model.

scholarly journals Quasar X-ray and UV flux, baryon acoustic oscillation, and Hubble parameter measurement constraints on cosmological model parameters

2020 ◽  
Vol 492 (3) ◽  
pp. 4456-4468 ◽  
Author(s):  
Narayan Khadka ◽  
Bharat Ratra
Keyword(s):  
Hubble Parameter ◽  
Cold Dark Matter ◽  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Joint Analysis ◽  
Model Parameters ◽  
Baryon Acoustic Oscillation ◽  
Current Standard ◽  
X Ray ◽  
Flux Measurements

ABSTRACT We use the 2015 Risaliti and Lusso compilation of 808 X-ray and UV flux measurements of quasars (QSOs) in the redshift range 0.061 ≤ z ≤ 6.28, alone and in conjunction with baryon acoustic oscillation (BAO) and Hubble parameter [H(z)] measurements, to constrain cosmological parameters in six cosmological models. The QSO data constraints are significantly weaker than, but consistent with, those from the H(z) + BAO data. A joint analysis of the QSO + H(z) + BAO data is consistent with the current standard model, spatially flat Λ cold dark matter, but mildly favours closed spatial hypersurfaces and dynamical dark energy.

scholarly journals Standardizing Dainotti-correlated gamma-ray bursts, and using them with standardized Amati-correlated gamma-ray bursts to constrain cosmological model parameters

2021 ◽  
Author(s):  
Shulei Cao ◽  
Narayan Khadka ◽  
Bharat Ratra
Keyword(s):  
Cosmological Model ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Model Parameters ◽  
Data Sets ◽  
Density Parameter ◽  
Cosmological Constraints ◽  
Cosmological Expansion ◽  
Model Independent ◽  
Lower Limits

Abstract We show that each of the three Dainotti-correlated gamma-ray burst (GRB) data sets recently compiled by Wang et al. and Hu et al., that together probe the redshift range 0.35 ≤ z ≤ 5.91, obey cosmological-model-independent Dainotti correlations and so are standardizable. We use these GRB data in conjunction with the best currently-available Amati-correlated GRB data, that probe 0.3399 ≤ z ≤ 8.2, to constrain cosmological model parameters. The resulting cosmological constraints are weak, providing lower limits on the non-relativistic matter density parameter, mildly favoring non-zero spatial curvature, and largely consistent with currently accelerated cosmological expansion as well as with constraints determined from better-established data.

scholarly journals An accelerating cosmological model from a parametrization of Hubble parameter

2019 ◽  
Vol 35 (05) ◽  
pp. 2050011 ◽  
Author(s):  
S. K. J. Pacif ◽  
Md Salahuddin Khan ◽  
L. K. Paikroy ◽  
Shalini Singh
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Hubble Parameter ◽  
Cosmological Parameters ◽  
Cosmic Time ◽  
Solution Procedure ◽  
Cosmic Acceleration ◽  
Model Parameters ◽  
Late Time ◽  
Field Equations

In view of late-time cosmic acceleration, a dark energy cosmological model is revisited wherein Einstein’s cosmological constant is considered as a candidate of dark energy. Exact solution of Einstein field equations (EFEs) is derived in a homogeneous isotropic background in classical general relativity. The solution procedure is adopted in a model-independent way (or the cosmological parametrization). A simple parametrization of the Hubble parameter (H) as a function of cosmic time t is considered which yields an exponential type of evolution of the scale factor (a) and also shows a negative value of deceleration parameter at the present time with a signature flip from early deceleration to late acceleration. Cosmological dynamics of the model obtained have been discussed illustratively for different phases of the evolution of the universe. The evolution of different cosmological parameters is shown graphically for flat and closed cases of Friedmann–Lemaitre–Robertson–Walker (FLRW) spacetime for the presented model (open case is incompatible to the present scenario). We have also constrained our model parameters with the updated (36 points) observational Hubble dataset.

scholarly journals Constraining the ΛCDM and Galileon models with recent cosmological data

2017 ◽  
Vol 600 ◽  
pp. A40 ◽  
Author(s):  
J. Neveu ◽  
V. Ruhlmann-Kleider ◽  
P. Astier ◽  
M. Besançon ◽  
J. Guy ◽  
...  
Keyword(s):  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Gravity Models ◽  
Accelerated Expansion ◽  
Data Sets ◽  
Late Time ◽  
Lunar Laser Ranging ◽  
Cosmological Constraints ◽  
Cosmological Data ◽  
Speed Of Propagation

Aims. The Galileon theory belongs to the class of modified gravity models that can explain the late-time accelerated expansion of the Universe. In previous works, cosmological constraints on the Galileon model were derived, both in the uncoupled case and with a disformal coupling of the Galileon field to matter. There, we showed that these models agree with the most recent cosmological data. In this work, we used updated cosmological data sets to derive new constraints on Galileon models, including the case of a constant conformal Galileon coupling to matter. We also explored the tracker solution of the uncoupled Galileon model. Methods. After updating our data sets, especially with the latest Planck data and baryonic acoustic oscillation (BAO) measurements, we fitted the cosmological parameters of the ΛCDM and Galileon models. The same analysis framework as in our previous papers was used to derive cosmological constraints, using precise measurements of cosmological distances and of the cosmic structure growth rate. Results. We show that all tested Galileon models are as compatible with cosmological data as the ΛCDM model. This means that present cosmological data are not accurate enough to distinguish clearly between the two theories. Among the different Galileon models, we find that a conformal coupling is not favoured, contrary to the disformal coupling which is preferred at the 2.3σ level over the uncoupled case. The tracker solution of the uncoupled Galileon model is also highly disfavoured owing to large tensions with supernovae and Planck+BAO data. However, outside of the tracker solution, the general uncoupled Galileon model, as well as the general disformally coupled Galileon model, remain the most promising Galileon scenarios to confront with future cosmological data. Finally, we also discuss constraints coming from the Lunar Laser Ranging experiment and gravitational wave speed of propagation.

scholarly journals Cosmological impact of redshift drift measurements

2021 ◽  
Vol 508 (1) ◽  
pp. L53-L57
Author(s):  
J Esteves ◽  
C J A P Martins ◽  
B G Pereira ◽  
C S Alves
Keyword(s):  
Energy Equation ◽  
Cosmological Parameters ◽  
Model Parameters ◽  
Merit Functions ◽  
Large Telescope ◽  
Trade Offs ◽  
Redshift Drift ◽  
Final Design ◽  
Model Independent ◽  
Better Than

ABSTRACT The redshift drift is a model-independent probe of fundamental cosmology, but choosing a fiducial model one can also use it to constrain the model parameters. We compare the constraining power of redshift drift measurements by the Extremely Large Telescope (ELT), as studied by Liske et al., with that of two recently proposed alternatives: the cosmic accelerometer of Eikenberry et al., and the differential redshift drift of Cooke. We find that the cosmic accelerometer with a 6-yr baseline leads to weaker constraints than those of the ELT (by 60 per cent); however, with identical time baselines it outperforms the ELT by up to a factor of 6. The differential redshift drift always performs worse than the standard approach if the goal is to constrain the matter density; however, it can perform significantly better than it if the goal is to constrain the dark energy equation of state. Our results show that accurately measuring the redshift drift and using these measurements to constrain cosmological parameters are different merit functions: an experiment optimized for one of them will not be optimal for the other. These non-trivial trade-offs must be kept in mind as next-generation instruments enter their final design and construction phases.

scholarly journals Methods for cluster cosmology and application to the SDSS in preparation for DES Year 1 release

2019 ◽  
Vol 488 (4) ◽  
pp. 4779-4800 ◽  
Author(s):  
M Costanzi ◽  
E Rozo ◽  
M Simet ◽  
Y Zhang ◽  
A E Evrard ◽  
...  
Keyword(s):  
Cold Dark Matter ◽  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Big Bang ◽  
Sloan Digital Sky Survey ◽  
Selection Function ◽  
Mass Relation ◽  
Data Set ◽  
Dark Energy Survey ◽  
Future Work

ABSTRACT We implement the first blind analysis of cluster abundance data to derive cosmological constraints from the abundance and weak lensing signal of redMaPPer clusters in the Sloan Digital Sky Survey (SDSS). We simultaneously fit for cosmological parameters and the richness–mass relation of the clusters. For a flat Λ cold dark matter cosmological model with massive neutrinos, we find $S_8 \equiv \sigma _{8}(\Omega _\mathrm{ m}/0.3)^{0.5}=0.79^{+0.05}_{-0.04}$. This value is both consistent and competitive with that derived from cluster catalogues selected in different wavelengths. Our result is also consistent with the combined probes analyses by the Dark Energy Survey (DES), the Kilo-Degree Survey (KiDS), and with the cosmic microwave background (CMB) anisotropies as measured by Planck. We demonstrate that the cosmological posteriors are robust against variation of the richness–mass relation model and to systematics associated with the calibration of the selection function. In combination with baryon acoustic oscillation data and big bang nucleosynthesis data (Cooke et al.), we constrain the Hubble rate to be h = 0.66 ± 0.02, independent of the CMB. Future work aimed at improving our understanding of the scatter of the richness–mass relation has the potential to significantly improve the precision of our cosmological posteriors. The methods described in this work were developed for use in the forthcoming analysis of cluster abundances in the DES. Our SDSS analysis constitutes the first part of a staged-unblinding analysis of the full DES data set.

scholarly journals Tension with the flat ΛCDM model from a high-redshift Hubble diagram of supernovae, quasars, and gamma-ray bursts

2019 ◽  
Vol 628 ◽  
pp. L4 ◽  
Author(s):  
E. Lusso ◽  
E. Piedipalumbo ◽  
G. Risaliti ◽  
M. Paolillo ◽  
S. Bisogni ◽  
...  
Keyword(s):  
Cold Dark Matter ◽  
Gamma Ray ◽  
High Redshift ◽  
Cosmological Parameters ◽  
New Physics ◽  
Gamma Ray Bursts ◽  
Hubble Diagram ◽  
Data Set ◽  
Λcdm Model ◽  
Model Independent

In the current framework, the standard parametrization of our Universe is the so-called Lambda cold dark matter (ΛCDM) model. Recently, a ∼4σ tension with the ΛCDM model was shown to exist via a model-independent parametrization of a Hubble diagram of type Ia supernovae (SNe Ia) from the JLA survey and quasars. Model-independent approaches and independent samples over a wide redshift range are key to testing this tension and any possible systematic errors. Here we present an analysis of a combined Hubble diagram of SNe Ia, quasars, and gamma-ray bursts (GRBs) to check the agreement of the quasar and GRB cosmological parameters at high redshifts (z >  2) and to test the concordance flat ΛCDM model with improved statistical accuracy. We build a Hubble diagram with SNe Ia, quasars, and GRBs, where quasars are standardised through the observed non-linear relation between their ultraviolet and X-ray emission and GRBs through the correlation between the spectral peak energy and the isotropic-equivalent radiated energy (the so-called Amati relation). We fit the data with cosmographic models consisting of a fourth-order logarithmic polynomial and a fifth-order linear polynomial, and compare the results with the expectations from a flat ΛCDM model. We confirm the tension between the best-fit cosmographic parameters and the ΛCDM model at ∼4σ with SNe Ia and quasars, at ∼2σ with SNe Ia and GRBs, and at > 4σ with the whole SNe Ia+quasars+GRB data set. The completely independent high-redshift Hubble diagrams of quasars and GRBs are fully consistent with each other, strongly suggesting that the deviation from the standard model is not due to unknown systematic effects but to new physics.

scholarly journals Cosmological constraints from Planck galaxy clusters with CMB lensing mass bias calibration

2019 ◽  
Vol 489 (1) ◽  
pp. 401-419 ◽  
Author(s):  
Íñigo Zubeldia ◽  
Anthony Challinor
Keyword(s):  
Galaxy Clusters ◽  
Cosmological Parameters ◽  
Mass Scale ◽  
Model Parameters ◽  
Cosmological Constraints ◽  
Cluster Sample ◽  
Mass Bias ◽  
Cluster Mass ◽  
Λcdm Model ◽  
The Absolute

ABSTRACT We present a new cosmological analysis of the galaxy clusters in the Planck MMF3 cosmology sample with a cosmic microwave background (CMB) lensing calibration of the cluster masses. As demonstrated by Planck, galaxy clusters detected via the Sunyaev–Zel’dovich (SZ) effect offer a powerful way to constrain cosmological parameters such as Ωm and σ8. Determining the absolute cluster mass scale is, however, difficult, and some recent calibrations have yielded cosmological constraints in apparent tension with constraints in the ΛCDM model derived from the power spectra of the primary CMB anisotropies. In order to calibrate the absolute mass scale of the full Planck cluster sample, we remeasure the masses of all 433 clusters through their weak lensing signature in the CMB temperature anisotropies as measured by Planck. We perform a joint Bayesian analysis of the cluster counts and masses taking as input the estimated cluster masses, SZ signal-to-noise ratios, and redshifts. Our analysis properly accounts for selection effects in the construction of the cluster sample. We find σ8(Ωm/0.33)0.25 = 0.765 ± 0.035 and $1-b_{\rm {SZ}} = 0.71 \pm 0.10$, where the mass bias factor $1-b_{\rm {SZ}}$ relates cluster mass to the SZ mass that appears in the X-ray-calibrated cluster scaling relations. We find no evidence for tension with the Planck primary CMB constraints on ΛCDM model parameters.

Quantification of amorphous siliceous fly ash in hydrated blended cement pastes by X-ray powder diffraction

2019 ◽  
Vol 52 (6) ◽  
pp. 1358-1370 ◽  
Author(s):  
Xuerun Li ◽  
Ruben Snellings ◽  
Karen L. Scrivener
Keyword(s):  
Fly Ash ◽  
Powder Diffraction ◽  
Isothermal Calorimetry ◽  
Blended Cement ◽  
Quantitative Phase Analysis ◽  
Model Parameters ◽  
Hydrated Cement ◽  
Cement Sample ◽  
Data Set ◽  
X Ray

X-ray powder diffraction (XRPD)-based quantitative phase analysis is a common technique for studying the hydration of cementitious systems. Hydrated cements often comprise several amorphous or nanocrystalline phases. This paper presents a protocol for the quantification of amorphous siliceous fly ash in hydrated cement using XRPD based on the Rietveld PONKCS (partial or no known crystal structure) method. The protocol is validated by comparison against independent measurements, such as Ca(OH)2 content by thermogravimetry and isothermal calorimetry to evaluate the fly ash degree of reaction. A sensitivity analysis of the protocol was carried out to test the robustness of the results with regard to sample preparation, data collection strategies and refinement model parameters. The key sensitive aspects of the protocol are (i) the preservation and preparation of the hydrated cement sample for XRPD measurement, (ii) the selection of a 2θ angular range for the Rietveld analysis that avoids low-angle scattering interferences, and (iii) the use of the peak profile to account for the contribution of other amorphous phases such as the diffraction pattern of nanocrystalline calcium silicate hydrate (C–S–H). The results show good accuracy in terms of quantification if the initial fly ash content is more than 10 wt%. Example TOPAS fly ash and C–S–H codes, as well as the raw XRPD data set, are provided.

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