Improved Distances to Type Ia Supernovae with Multicolor Light‐Curve Shapes: MLCS2k2

Jha, Saurabh W.; Riess, Adam G.; Kirshner, R.

doi:10.1086/512054

Cited by 828 publications

(1,217 citation statements)

References 108 publications

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“…In contrast to the SALT fitters, MLCS2k2 (Jha et al 2007) includes the intrinsic colour in the shape parameter Δ assuming a broader-bluer and narrower-redder relation. The host-galaxy extinction parameter A v is then determined separately.…”

Section: Supernova Data and Resultsmentioning

confidence: 99%

Constraints on anisotropic cosmic expansion from supernovae

Kalus

Schwarz

Seikel

et al. 2013

A&A

105

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Aims. We test the isotropy of the expansion of the Universe by estimating the hemispherical anisotropy of supernova type Ia (SN Ia) Hubble diagrams at low redshifts (z < 0.2). Methods. We compare the best fit Hubble diagrams in pairs of hemispheres and search for the maximal asymmetric orientation. For an isotropic Universe, we expect only a small asymmetry due to noise and the presence of nearby structures. This test does not depend on the assumed content of the Universe, the assumed model of gravity, or the spatial curvature of the Universe. The expectation for possible fluctuations due to large scale structure is evaluated for the Λ cold dark matter (ΛCDM) model and is compared to the supernova data from the Constitution set for four different light curve fitters, thus allowing a study of the systematic effects. Results. The expected order of magnitude of the hemispherical asymmetry of the Hubble expansion agrees with the observed one. The direction of the Hubble asymmetry is established at 95% confidence level (C.L.) using both, the MLCS2k2 and the SALT II light curve fitter. The highest expansion rate is found towards ( , b) ≈ (−35 • , −19 • ), which agrees with directions reported by other studies. Its amplitude is not in contradiction to expectations from the ΛCDM model. The measured Hubble anisotropy is ΔH/H ∼ 0.026. With 95% C.L. the expansion asymmetry is ΔH/H < 0.038.

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Section: Supernova Data and Resultsmentioning

confidence: 99%

Constraints on anisotropic cosmic expansion from supernovae

Kalus

Schwarz

Seikel

et al. 2013

A&A

105

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“…The maximum radius rmax = 75h −1 Mpc, corresponding to the Hubble velocity czmax = 7500 km s −1 , is commonly adopted as the limiting value separating lowz SNIa, whose Hubble diagram is likely to be significantly perturbed by local inhomogeneities (Zehavi et al 1998;Jha et al 2007), from high-z ones, which are thought to probe the global expansion of the Universe (Riess et al 2011).…”

Section: Random Observers In Spacementioning

confidence: 99%

“…Comparison with observational constraints on H loc can only be made in terms of the relative differences between the Hubble parameters determined from data sets probing H loc at different scales. Here we consider two combinations of measurements which have recently attracted considerable attention: i. the difference in the determination of H loc between the z < 0.025 and 0.025 < z < 0.10 SNIa samples reported by Jha et al (2007) and ii. the difference between the expansion rate determined by using nearby SNIa with an improved distance calibration from Cepheids (Riess et al 2011) and that by using CMB observations from Planck (Planck Collaboration et al 2013).…”

Section: Comparison With Observationsmentioning

confidence: 99%

Cosmic variance of the local Hubble flow in large-scale cosmological simulations

Wojtak¹,

Knebe²,

Watson³

et al. 2013

Monthly Notices of the Royal Astronomical Society

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The increasing precision in the determination of the Hubble parameter has reached a per cent level at which large-scale cosmic flows induced by inhomogeneities of the matter distribution become non-negligible. Here we use large-scale cosmological Nbody simulations to study statistical properties of the local Hubble parameter as measured by local observers. We show that the distribution of the local Hubble parameter depends not only on the scale of inhomogeneities, but also on how one defines the positions of observers in the cosmic web and what reference frame is used. Observers located in random dark matter haloes measure on average lower expansion rates than those at random positions in space or in the centres of cosmic voids, and this effect is stronger from the halo rest frames compared to the CMB rest frame. We compare the predictions for the local Hubble parameter with observational constraints based on type Ia supernovae (SNIa) and CMB observations. Due to cosmic variance, for observers located in random haloes we show that the Hubble constant determined from nearby SNIa may differ from that measured from the CMB by ±0.8 per cent at 1σ statistical significance. This scatter is too small to significantly alleviate a recently claimed discrepancy between current measurements assuming a flat ΛCDM model. However, for observers located in the centres of the largest voids permitted by the standard ΛCDM model, we find that Hubble constant measurements from SNIa would be biased high by 5 per cent, rendering this tension inexistent in this extreme case.

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“…By contrast, the Multi-color Lightcurve Shape (Riess et al 1996;Jha et al 2007) approach simultaneously infers the Phillips corrections and the cosmological parameters of interest, while explicitly modeling the dust absorption and reddening in the host galaxy. Recently, a fully Bayesian, hierarchical model approach to LC fitting has emerged (Mandel et al 2009(Mandel et al , 2011, but this so-called BAYESN algorithm has not yet been applied for inferring cosmological parameters.…”

Section: Introductionmentioning

confidence: 99%

BAHAMAS: NEW ANALYSIS OF TYPE Ia SUPERNOVAE REVEALS INCONSISTENCIES WITH STANDARD COSMOLOGY

Shariff

Jiao

Trotta

et al. 2016

ApJ

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We present results obtained by applying our BAyesian HierArchical Modeling for the Analysis of Supernova cosmology (BAHAMAS) software package to the 740 spectroscopically confirmed supernovae of type Ia (SNe Ia) from the "Joint Light-curve Analysis" (JLA) data set. We simultaneously determine cosmological parameters and standardization parameters, including corrections for host galaxy mass, residual scatter, and object-by-object intrinsic magnitudes. Combining JLA and Planck data on the cosmic microwave background, we find significant discrepancies in cosmological parameter constraints with respect to the standard analysis: we find W =  0.399 0.027 m , s 2.8 higher than previously reported, and = - w 0.910 0.045, s 1.6 higher than the standard analysis. We determine the residual scatter to be s =  0.104 0.005 res . We confirm (at the 95% probability level) the existence of two subpopulations segregated by host galaxy mass, separated at, differing in mean intrinsic magnitude by 0.055 ± 0.022 mag, lower than previously reported. Cosmological parameter constraints, however, are unaffected by the inclusion of corrections for host galaxy mass. We find s4 evidence for a sharp drop in the value of the color correction parameter, ( ) b z , at a redshift =  z 0.662 0.055 t . We rule out some possible explanations for this behavior, which remains unexplained.

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Improved Distances to Type Ia Supernovae with Multicolor Light‐Curve Shapes: MLCS2k2

Cited by 828 publications

References 108 publications

Constraints on anisotropic cosmic expansion from supernovae

Constraints on anisotropic cosmic expansion from supernovae

Cosmic variance of the local Hubble flow in large-scale cosmological simulations

BAHAMAS: NEW ANALYSIS OF TYPE Ia SUPERNOVAE REVEALS INCONSISTENCIES WITH STANDARD COSMOLOGY

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