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arXiv 1604.02809astro-ph.CO
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分离Lyman Alpha森林BAO异常

Isolating the Lyman Alpha Forest BAO Anomaly

Jarah Evslin

摘要:

在$z\sim 2.34$的莱曼$α$森林中的重子声振荡峰(BAO)与最佳拟合的普朗克$Λ$ CDM宇宙学之间有2.5-3 σ的差异。为了分离张力的起源,我们考虑了未锚定的BAO,其中标准的BAO标尺没有校准,消除了在红移之前对宇宙学的任何依赖$z\sim 2.34$。我们考虑在$z\sim 0.32$,0.57和2.34的BOSS BAO测量,使用角度和视线BAO尺度上的全二维约束,以及在$z\sim 0.106$和$z\sim 0.15$的6dF和SDSS的各向同性BAO测量。我们发现,$z>0.43$数据单独与$Λ$ CDM有2.9 σ的张力,无论是否有质量分数$Ω_m$和BAO标度$r_d H_0$的普朗克最佳拟合值,这表明张力不是来自$Λ$ CDM参数,而是来自暗能量演化本身,0.57<z<2.34。当包括由CMB测量的声学尺度时,这一结论得到支持,这进一步增加了张力并排除了具有恒定暗能量状态方程的解。包括低$z$ BAO数据,其本身与$Λ$ CDM一致,将张力降低到略高于2 sigma,然而在这种情况下,暗能量演化的CPL参数化仅产生适度的改善。

英文摘要:

A 2.5-3 sigma discrepancy has been reported between the baryonic acoustic oscillation peak (BAO) in the Lyman $α$ forest at $z\sim 2.34$ and the best fit Planck $Λ$CDM cosmology. To isolate the origin of the tension, we consider unanchored BAO, in which the standard BAO ruler is not calibrated, eliminating any dependence on cosmology before redshift $z\sim 2.34$. We consider BOSS BAO measurements at $z\sim 0.32$, 0.57 and 2.34, using the full 2-dimensional constraints on the angular and line of sight BAO scale, as well as isotropic BAO measurements by 6dF and SDSS at $z\sim 0.106$ and $z\sim 0.15$. We find that the $z>0.43$ data alone is in 2.9 sigma of tension with $Λ$CDM with or without the Planck best fit values of the mass fraction $Ω_m$ and the BAO scale $r_d H_0$, indicating that the tension arises not from the $Λ$CDM parameters but from the dark energy evolution itself at 0.57<z<2.34. This conclusion is supported when the acoustic scale measured by the CMB is included, which further increases the tension and excludes a solution with a constant dark energy equation of state. Including the low $z$ BAO data, which is itself consistent with $Λ$CDM, reduces the tension to just over 2 sigma, however in this case a CPL parametrization of the dark energy evolution yields only a modest improvement.

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