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arXiv 0712.0034astro-ph
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星系团奇异速度对暗能量的约束

Dark Energy Constraints from Galaxy Cluster Peculiar Velocities

Suman Bhattacharya, Arthur Kosowsky

摘要:

未来具有弧分分辨率和微开尔文温度灵敏度的多频微波背景实验将能够探测到动力学Sunyaev-Zeldovich(kSZ)效应,为测量大质量星系团的径向奇特速度提供一种方法。我们发现星系团特有的速度有可能限制几个暗能量参数。我们比较了三种速度统计(径向速度分布,平均成对流速度,速度关联函数),并分析了这些统计约束暗能量参数的相对优势。在这三个统计量中,平均成对流速度提供了对速度误差最不敏感的约束:当随机误差从100 km/s增加到500 km/s时,对参数的约束仅降低了两倍。我们还比较了星系团的速度与其他暗能量探测提出的暗能量工作组的报告。对于具有现实先验的星系团速度测量,对暗能量密度、暗能量状态方程及其演化的最终约束与超新星测量的约束相当,并且优于星系团计数和重子声学振荡;将速度添加到其他暗能量探测器中可以将对品质因数的约束提高两倍以上。对于即将到来的Sunyaev-Zeldovich星系团调查,即使是误差高达1000 km/s的速度测量,与单独使用星系团数量密度相比,也将大大改善宇宙学约束。

英文摘要:

Future multifrequency microwave background experiments with arcminute resolution and micro-Kelvin temperature sensitivity will be able to detect the kinetic Sunyaev-Zeldovich (kSZ) effect, providing a way to measure radial peculiar velocities of massive galaxy clusters. We show that cluster peculiar velocities have the potential to constrain several dark energy parameters. We compare three velocity statistics (the distribution of radial velocities, the mean pairwise streaming velocity, and the velocity correlation function) and analyze the relative merits of these statistics in constraining dark energy parameters. Of the three statistics, mean pairwise streaming velocity provides constraints that are least sensitive to velocity errors: the constraints on parameters degrades only by a factor of two when the random error is increased from 100 to 500 km/s. We also compare cluster velocities with other dark energy probes proposed in the Dark Energy Task Force report. For cluster velocity measurements with realistic priors, the eventual constraints on the dark energy density, the dark energy equation of state and its evolution are comparable to constraints from supernovae measurements, and better than cluster counts and baryon acoustic oscillations; adding velocity to other dark energy probes improves constraints on the figure of merit by more than a factor of two. For upcoming Sunyaev-Zeldovich galaxy cluster surveys, even velocity measurements with errors as large as 1000 km/s will substantially improve the cosmological constraints compared to using the cluster number density alone.

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