Searching for a preferred direction with Union2.1 data

Xiaofeng Yang; F. Y. Wang; Zhe Chu

doi:10.1093/mnras/stt2015

paper

Searching for a preferred direction with Union2.1 data

arXiv:1310.5211 · doi:10.1093/mnras/stt2015

Abstract

A cosmological preferred direction was reported from the type Ia supernovae (SNe Ia) data in recent years. We use the Union2.1 data to give a simple classification of such studies for the first time. Because the maximum anisotropic direction is independent of isotropic dark energy models, we adopt two cosmological models ( $Λ$ CDM, $w$ CDM) for the hemisphere comparison analysis and $Λ$ CDM model for dipole fit approach. In hemisphere comparison method, the matter density and the equation of state of dark energy are adopted as the diagnostic qualities in the $Λ$ CDM model and $w$ CDM model, respectively. In dipole fit approach, we fit the fluctuation of distance modulus. We find that there is a null signal for the hemisphere comparison method, while a preferred direction ( $b = - 14. 3^{\circ} \pm 10. 1^{\circ}, l = 307. 1^{\circ} \pm 16. 2^{\circ}$ ) for the dipole fit method. This result indicates that the dipole fit is more sensitive than the hemisphere comparison method.

8 pages, 2 figures, accepted for publication in MNRAS

Searching for a preferred direction with Union2.1 data

Abstract

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