Testing the isotropy of the Universe by using the JLA compilation of Type Ia supernovae

Lin, Hai-Nan; Wang, Sai; Chang, Zhe; Li, Xin

doi:10.1093/mnras/stv2804

Cited by 56 publications

(73 citation statements)

References 57 publications

(72 reference statements)

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“…A similar cosmic anisotropy has been found in the Union2.1 sample (Yang et al 2014;Javanmardi et al 2015;Bengaly et al 2015;Li et al 2015;Lin et al 2016b). Different with the Union2 or Union2.1 sample, the JLA sample doesn't show any convincing evidence for the existence of the cosmic anisotropy (Bengaly et al 2015;Lin et al 2016a;Chang et al 2018a;Wang & Wang 2018;Deng & Wei 2018b;Sun & Wang 2018a). Constraining the anisotropic amplitude and direction in ΛCDM, ωCDM and CPL models with the JLA sample gave a zero result (Lin et al 2016a).…”

Section: Introductionmentioning

confidence: 51%

Anisotropy of the Universe via the Pantheon supernovae sample revisited

Zhao

Zhou

Chang

2019

Monthly Notices of the Royal Astronomical Society

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We employ the hemisphere comparison (HC) method and the dipole fitting (DF) method to investigate the cosmic anisotropy in the recently released Pantheon sample of type Ia supernovae (SNe Ia) and five combinations among Pantheon. For the HC method, we find the maximum anisotropy level in the full Pantheon sample is AL max = 0.361 ± 0.070 and corresponding direction (l, b) = (123.05A robust check shows the statistical significance of maximum anisotropy level is about 2.1σ. We also find that the Low-z and SNLS subsamples have decisive impact on the overall anisotropy while other three subsamples have little impact. Moreover, the anisotropy level map significantly rely on the inhomogeneous distribution of SNe Ia in the sky. For the DF method, we find the dipole anisotropy in the Pantheon sample is very weak. The dipole magnitude is constrained to be less than 1.16 × 10 −3 at 95% confidence level. However, the dipole direction is well inferred by MCMC method and it points towards (l, b) = (306.00 •+82.95 • −125.01 • , −34.20 •+16.82 • −54.93 • ). This direction is very close to the axial direction to the plane of SDSS subsample. It may imply that SDSS subsample is the decisive part to the dipole anisotropy in the full Pantheon sample. All these facts imply that the cosmic anisotropy found in Pantheon sample significantly rely on the inhomogeneous distribution of SNe Ia in the sky. More homogeneous distribution of SNe Ia is necessary to search for a more convincing cosmic anisotropy.

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Section: Introductionmentioning

confidence: 51%

Anisotropy of the Universe via the Pantheon supernovae sample revisited

Zhao

Zhou

Chang

2019

Monthly Notices of the Royal Astronomical Society

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“…The dipole direction points * https://github.com/dscolnic/Pantheon † https://emcee.readthedocs.io/en/stable/ ‡ We use the highest posterior density (HPD) credible interval method to determine the 68% CL. Model At the end, we make some comparisons between the dipole directions mentioned above in the Pantheon sample with that derived from the Union2 sample [39], Union2.1 sample [44] and JLA sample [50]. The dipole directions in each SNe Ia sample are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Wang et al [55] used the JLA sample to constrain the anisotropic universe model with Bianchi-I metric and found the model was consistent with the isotropic universe. Constraining the anisotropic amplitude and direction in three different cosmological models of dark energy with the JLA sample gave a zero result [50]. Sang et al [57] performed a tomographic analysis on the JLA sample taking account of redshift dependence of SNe Ia color-luminosity parameter β in the dipole-modulated ΛCDM model, but they did not find any significant deviation from the isotropic universe.…”

Section: Introductionmentioning

confidence: 99%

Constraining the anisotropy of the Universe with the Pantheon supernovae sample *

2019

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We test the possible dipole anisotropy of a Finslerian cosmological model and other three dipolemodulated cosmological models, i.e., the dipole-modulated ΛCDM, wCDM and Chevallier-Polarski-Linder (CPL) model by using the recently released Pantheon sample of SNe Ia. The Markov chain Monte Carlo (MCMC) method is used to explore the whole parameter space. We find that the dipole anisotropy is very weak in all cosmological models used. Although the dipole amplitudes of four cosmological models are consistent with zero within 1σ uncertainty, the dipole directions are close to the axial direction to the plane of SDSS subsample among Pantheon. It may imply that the weak dipole anisotropy in the Pantheon sample originates from the inhomogeneous distribution of the SDSS subsample. More homogeneous distribution of SNe Ia is necessary to constrain the cosmic anisotropy.

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“…There are several evidences for this hypotheses. The recent analysis [35] showed that the dipole directions of two different Sne Ia data sets, Union 2 [36] and JLA [37], are inconsistent. The dipole directions of Union2 derived using two different methods are almost opposite [38].…”

Section: Discussionmentioning

confidence: 99%

Spatial and temporal variations of the fine-structure constant in the Finslerian universe

Lin

2017

Chinese Phys. C

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Recent observations show that the electromagnetic fine-structure constant, α e , may vary with space and time. In the framework of Finsler spacetime, we propose here an anisotropic cosmological model, in which both the spatial and temporal variations of α e are allowed. Our model naturally leads to the dipole structure of α e , and predicts that the dipole amplitude increases with time. We fit our model to the most up-to-date measurements of α e from the quasar absorption lines. It is found that the dipole direction points towards (l, b) = (330.2 • ± 7.3 • , −13.0 • ± 5.6 • ) in the galactic coordinates, and the anisotropic parameter is b 0 = (0.47 ± 0.09) × 10 −5 , which corresponds to a dipole amplitude (7.2 ± 1.4) × 10 −8 at redshift z = 0.015. This is well consistent with the upper limit of the variation of α e measured in the Milky Way. We also fit our model to the Union2.1 type Ia supernovae, and find that the preferred direction of Union2.1 is well consistent with the dipole direction of α e .

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Testing the isotropy of the Universe by using the JLA compilation of Type Ia supernovae

Cited by 56 publications

References 57 publications

Anisotropy of the Universe via the Pantheon supernovae sample revisited

Anisotropy of the Universe via the Pantheon supernovae sample revisited

Constraining the anisotropy of the Universe with the Pantheon supernovae sample *

Spatial and temporal variations of the fine-structure constant in the Finslerian universe

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