论文标题

使用随机秩序红移技术(排序),来自光度红移的星系相关函数和局部密度

Galaxy Correlation Function and Local Density from Photometric Redshifts Using the Stochastic Order Redshift Technique (SORT)

论文作者

Kakos, James, Primack, Joel R., Rodriguez-Puebla, Aldo, Tejos, Nicolas, Yung, L. Y. Aaron, Somerville, Rachel S.

论文摘要

随机秩序红移技术(排序)是一种简单,高效且健壮的方法,可改善宇宙学红移测量。该方法依赖于具有高质量红移的小($ \ sim $ 10%)参考样本。在每个星系周围的铅笔梁状子卷中,我们使用参考样品的精确DN/D $ Z $分布来恢复新的红移,并将它们分配给星系一对一,以便保留了Redshifts的原始等级顺序。保留等级顺序的动机是由以下事实激励:从高斯概率密度函数中绘制的随机变量具有不同的均值,但相等的标准偏差满足随机排序。在调查中每个星系周围的子卷重复该过程。这会导致每个星系,并分配了不确定的红移,可以从中确定新的红移估算值。较早的论文以$ z \ Lessim $ 0.2应用于模拟的斯隆数字天空调查,并准确地恢复了尺度上的两点相关函数$ \ gtrsim $ 4 $ h^{ - 1} $ mpc。在本文中,我们测试了跨越红移范围0.75 $ <z <z <$ 2.25的调查中排序的性能。我们使用了两项模拟调查,这些模拟调查是从小型的Multidark-Planck和Bolshoi-Planck N体型模拟的,这些模拟与Santa Cruz半分析模型填充的暗物质光环。我们发现这种类型能够改善红移估计值并恢复宇宙网络的独特大规模特征。此外,它提供了红移空间两点相关函数的无偏估计$ \ gtrsim $ \ gtrsim $ 2.5 $ h^{ - 1} $ mpc,以及平均或更高密度的区域的局部密度。这可以提高人们对星系属性与其本地环境的关系的了解。

The stochastic order redshift technique (SORT) is a simple, efficient, and robust method to improve cosmological redshift measurements. The method relies upon having a small ($\sim$10 per cent) reference sample of high-quality redshifts. Within pencil-beam-like sub-volumes surrounding each galaxy, we use the precise dN/d$z$ distribution of the reference sample to recover new redshifts and assign them one-to-one to galaxies such that the original rank order of redshifts is preserved. Preserving the rank order is motivated by the fact that random variables drawn from Gaussian probability density functions with different means but equal standard deviations satisfy stochastic ordering. The process is repeated for sub-volumes surrounding each galaxy in the survey. This results in every galaxy with an uncertain redshift being assigned multiple "recovered" redshifts from which a new redshift estimate can be determined. An earlier paper applied SORT to a mock Sloan Digital Sky Survey at $z \lesssim$ 0.2 and accurately recovered the two-point correlation function on scales $\gtrsim$4 $h^{-1}$Mpc. In this paper, we test the performance of SORT in surveys spanning the redshift range 0.75$<z<$2.25. We used two mock surveys extracted from the Small MultiDark-Planck and Bolshoi-Planck N-body simulations with dark matter haloes that were populated by the Santa Cruz semi-analytic model. We find that SORT is able to improve redshift estimates and recover distinctive large-scale features of the cosmic web. Further, it provides unbiased estimates of the redshift-space two-point correlation function $ξ(s)$ on scales $\gtrsim$2.5 $h^{-1}$Mpc, as well as local densities in regions of average or higher density. This may allow improved understanding of how galaxy properties relate to their local environments.

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