scholarly journals Utilizing the Updated Gamma-Ray Bursts and Type Ia Supernovae to Constrain the Cardassian Expansion Model and Dark Energy

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Jun-Jie Wei ◽  
Qing-Bo Ma ◽  
Xue-Feng Wu
Keyword(s):  
Dark Energy ◽  
Gamma Ray ◽  
Interpolation Method ◽  
Spline Interpolation ◽  
Confidence Region ◽  
Type Ia Supernovae ◽  
Distance Modulus ◽  
Type Ia ◽  
Ia Supernovae ◽  
Expansion Model

We update gamma-ray burst (GRB) luminosity relations among certain spectral and light-curve features with 139 GRBs. The distance modulus of 82 GRBs atz>1.4can be calibrated with the sample atz≤1.4by using the cubic spline interpolation method from the Union2.1 Type Ia supernovae (SNe Ia) set. We investigate the joint constraints on the Cardassian expansion model and dark energy with 580 Union2.1 SNe Ia sample(z<1.4)and 82 calibrated GRBs’ data(1.4<z≤8.2). In ΛCDM, we find that adding 82 high-zGRBs to 580 SNe Ia significantly improves the constraint onΩm-ΩΛplane. In the Cardassian expansion model, the best fit isΩm=0.24-0.15+0.15andn=0.16-0.52+0.30  (1σ), which is consistent with the ΛCDM cosmology(n=0)in the1σconfidence region. We also discuss two dark energy models in which the equation of statew(z)is parameterized asw(z)=w0andw(z)=w0+w1z/(1+z), respectively. Based on our analysis, we see that our universe at higher redshift up toz=8.2is consistent with the concordance model within1σconfidence level.

scholarly journals First cosmology results using Type IA supernovae from the dark energy survey: effects of chromatic corrections to supernova photometry on measurements of cosmological parameters

2019 ◽  
Vol 485 (4) ◽  
pp. 5329-5344 ◽  
Author(s):  
J Lasker ◽  
R Kessler ◽  
D Scolnic ◽  
D Brout ◽  
D L Burke ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Critical Density ◽  
Transmission Function ◽  
Type Ia Supernovae ◽  
Distance Modulus ◽  
Dark Energy Survey ◽  
Type Ia ◽  
Ia Supernovae ◽  
Energy Survey

Abstract Calibration uncertainties have been the leading systematic uncertainty in recent analyses using Type Ia supernovae (SNe Ia) to measure cosmological parameters. To improve the calibration, we present the application of spectral energy distribution-dependent ‘chromatic corrections’ to the SN light-curve photometry from the Dark Energy Survey (DES). These corrections depend on the combined atmospheric and instrumental transmission function for each exposure, and they affect photometry at the 0.01 mag (1 per cent) level, comparable to systematic uncertainties in calibration and photometry. Fitting our combined DES and low-z SN Ia sample with baryon acoustic oscillation (BAO) and cosmic microwave background (CMB) priors for the cosmological parameters Ωm (the fraction of the critical density of the universe comprised of matter) and w (the dark energy equation of state parameter), we compare those parameters before and after applying the corrections. We find the change in w and Ωm due to not including chromatic corrections is −0.002 and 0.000, respectively, for the DES-SN3YR sample with BAO and CMB priors, consistent with a larger DES-SN3YR-like simulation, which has a w-change of 0.0005 with an uncertainty of 0.008 and an Ωm change of 0.000 with an uncertainty of 0.002. However, when considering samples on individual CCDs we find large redshift-dependent biases (∼0.02 in distance modulus) for SN distances.

scholarly journals SNe data analysis in variable speed of light cosmologies without cosmological constant

2014 ◽  
Vol 29 (24) ◽  
pp. 1450103 ◽  
Author(s):  
Pengfei Zhang ◽  
Xinhe Meng
Keyword(s):  
Dark Energy ◽  
Scale Factor ◽  
Model Parameters ◽  
Type Ia Supernovae ◽  
Distance Modulus ◽  
Data Sets ◽  
Variable Speed ◽  
Speed Of Light ◽  
Type Ia ◽  
Ia Supernovae

In this work, we aim to show the possibilities of the variable speed of light (VSL) theory in explaining the type Ia supernovae (SNe) observations without introducing dark energy. The speed of light is assumed to be scale factor-dependent, which is the most popular assumption in VSL theory. We show the modified calculation of the distance modulus and the validity of the redshift-scale factor relation in VSL theory. Three different models of VSL are tested SNe data-sets with proper constraints on the model parameters. The comparison of the three models and flat ΛCDM in distance modulus is showed. Some basic problems and the difficulties of the confirmation of the VSL theory are also discussed.

scholarly journals Model-independent cosmic acceleration and redshift-dependent intrinsic luminosity in type-Ia supernovae

2019 ◽  
Vol 625 ◽  
pp. A15 ◽  
Author(s):  
I. Tutusaus ◽  
B. Lamine ◽  
A. Blanchard
Keyword(s):  
Spline Interpolation ◽  
High Redshift ◽  
Cosmic Acceleration ◽  
Expansion Rate ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Model Independent ◽  
Ia Supernovae ◽  
The Universe ◽  
Intrinsic Luminosity

Context. The cosmological concordance model (ΛCDM) is the current standard model in cosmology thanks to its ability to reproduce the observations. The first observational evidence for this model appeared roughly 20 years ago from the type-Ia supernovae (SNIa) Hubble diagram from two different groups. However, there has been some debate in the literature concerning the statistical treatment of SNIa, and their stature as proof of cosmic acceleration. Aims. In this paper we relax the standard assumption that SNIa intrinsic luminosity is independent of redshift, and examine whether it may have an impact on our cosmological knowledge and more precisely on the accelerated nature of the expansion of the universe. Methods. To maximise the scope of this study, we do not specify a given cosmological model, but we reconstruct the expansion rate of the universe through a cubic spline interpolation fitting the observations of the different cosmological probes: SNIa, baryon acoustic oscillations (BAO), and the high-redshift information from the cosmic microwave background (CMB). Results. We show that when SNIa intrinsic luminosity is not allowed to vary as a function of redshift, cosmic acceleration is definitely proven in a model-independent approach. However, allowing for redshift dependence, a nonaccelerated reconstruction of the expansion rate is able to fit, at the same level of ΛCDM, the combination of SNIa and BAO data, both treating the BAO standard ruler rd as a free parameter (not entering on the physics governing the BAO), and adding the recently published prior from CMB observations. We further extend the analysis by including the CMB data. In this case we also consider a third way to combine the different probes by explicitly computing rd from the physics of the early universe, and we show that a nonaccelerated reconstruction is able to nicely fit this combination of low- and high-redshift data. We also check that this reconstruction is compatible with the latest measurements of the growth rate of matter perturbations. We finally show that the value of the Hubble constant (H0) predicted by this reconstruction is in tension with model-independent measurements. Conclusions. We present a model-independent reconstruction of a nonaccelerated expansion rate of the universe that is able to fit all the main background cosmological probes nicely. However, the predicted value of H0 is in tension with recent direct measurements. Our analysis points out that a final reliable and consensual value for H0 is critical to definitively prove cosmic acceleration in a model-independent way.

scholarly journals Observations of Type Ia Supernovae and Challenges for Cosmology

2005 ◽  
Vol 192 ◽  
pp. 525-533
Author(s):  
Weidong Li ◽  
Alexei V. Filippenko
Keyword(s):  
Dark Energy ◽  
Light Curve ◽  
Rise Time ◽  
Accelerating Universe ◽  
Type Ia Supernovae ◽  
Hubble Diagram ◽  
High Quality ◽  
Type Ia ◽  
Secondary Parameter ◽  
Ia Supernovae

SummaryObservations of Type Ia supernovae (SNe Ia) reveal correlations between their luminosities and light-curve shapes, and between their spectral sequence and photometric sequence. Assuming SNe Ia do not evolve at different redshifts, the Hubble diagram of SNe Ia may indicate an accelerating Universe, the signature of a cosmological constant or other forms of dark energy. Several studies raise concerns about the evolution of SNe Ia (e.g., the peculiarity rate, the rise time, and the color of SNe Ia at different redshifts), but all these studies suffer from the difficulties of obtaining high-quality spectroscopy and photometry for SNe Ia at high redshifts. There are also some troubling cases of SNe Ia that provide counter examples to the observed correlations, suggesting that a secondary parameter is necessary to describe the whole SN Ia family. Understanding SNe Ia both observationally and theoretically will be the key to boosting confidence in the SN Ia cosmological results.

scholarly journals First cosmological results using Type Ia supernovae from the Dark Energy Survey: measurement of the Hubble constant

2019 ◽  
Vol 486 (2) ◽  
pp. 2184-2196 ◽  
Author(s):  
E Macaulay ◽  
R C Nichol ◽  
D Bacon ◽  
D Brout ◽  
T M Davis ◽  
...  
Keyword(s):  
Dark Energy ◽  
Hubble Constant ◽  
Type Ia Supernovae ◽  
Distance Measurements ◽  
Dark Energy Survey ◽  
Systematic Uncertainties ◽  
Type Ia ◽  
Ia Supernovae ◽  
Energy Survey ◽  
Inverse Distance

ABSTRACT We present an improved measurement of the Hubble constant (H0) using the ‘inverse distance ladder’ method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) at redshift 0.018 &lt; z &lt; 0.85 to existing distance measurements of 122 low-redshift (z &lt; 0.07) SNe Ia (Low-z) and measurements of Baryon Acoustic Oscillations (BAOs). Whereas traditional measurements of H0 with SNe Ia use a distance ladder of parallax and Cepheid variable stars, the inverse distance ladder relies on absolute distance measurements from the BAOs to calibrate the intrinsic magnitude of the SNe Ia. We find H0 = 67.8 ± 1.3 km s−1 Mpc−1 (statistical and systematic uncertainties, 68 per cent confidence). Our measurement makes minimal assumptions about the underlying cosmological model, and our analysis was blinded to reduce confirmation bias. We examine possible systematic uncertainties and all are below the statistical uncertainties. Our H0 value is consistent with estimates derived from the Cosmic Microwave Background assuming a ΛCDM universe.

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