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arXiv 1901.05705astro-ph.CO
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利用宇宙计时器和HII哈勃图测量空间曲率

A Model-Independent Measurement of the Spatial Curvature using Cosmic Chronometers and the HII Hubble Diagram

Jing Zheng, Fulvio Melia, Tong-Jie Zhang

摘要:

我们提出了一个独立于模型的方法来确定宇宙曲率的哈勃参数$H(z)$测量宇宙计时器和共动距离$D(z)$推断的HII星系。我们采用高斯过程来平滑距离的测量,并将其与$H(z)$的$30$值相匹配。曲率参数$Ω_k$可以针对每个这样的对单独地获得。完整样本的加权平均值为$Ω_k=-0.0013\pm0.0004$,表明偏向负值。曲率测量的准确性随着红移的增加而提高,然而,考虑到与局部不均匀性相关的可能的系统效应。因此,我们还分析了一个高红移($z>1.5$)子样本本身,这是更有可能反映宇宙的几何形状在大,光滑的尺度。我们发现,对于这组数据,$Ω_k=-0.0111\pm0.0416$,与零一致,优于$1σ$。这一结果与从宇宙微波背景观测中推断出的宇宙空间平坦相一致。我们希望这种方法产生更严格的约束曲率参数与未来,更准确的观测HII星系在高$z$。

英文摘要:

We propose a model-independent way to determine the cosmic curvature using the Hubble parameter $H(z)$ measured with cosmic chronometers and the comoving distance $D(z)$ inferred from HII galaxies. We employ Gaussian processes to smooth the measure of distance and match it to $30$ values of $H(z)$. The curvature parameter $Ω_k$ may be obtained individually for each such pair. The weighted average for the complete sample is $Ω_k=-0.0013\pm0.0004$, suggesting a bias towards negative values. The accuracy of the curvature measurement improves with increased redshift, however, given possible systematic effects associated with local inhomogeneities. We therefore also analyze a high-redshift ($z>1.5$) sub-sample on its own, which is more likely to reflect the geometry of the Universe on large, smooth scales. We find for this set of data that $Ω_k=-0.0111\pm0.0416$, consistent with zero to better than $1σ$. This result is in agreement with the spatially flat universe inferred from the cosmic microwave background observations. We expect this method to yield even tighter constraints on the curvature parameter with future, more accurate observations of HII galaxies at high $z$.

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