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arXiv 1302.1195astro-ph.CO
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用数密度选择通过宇宙时追踪Galerkin

Tracing Galaxies Through Cosmic Time with Number Density Selection

Joel Leja, Pieter van Dokkum, Marijn Franx

摘要:

观测研究星系形成的一个核心挑战是如何将祖先星系与它们在较低红移的后代星系联系起来。一种有希望的方法是以固定的数量密度连接星系,而不是固定的光度或质量。如果恒星的质量等级在整个宇宙时间内是广泛守恒的,那么这种方法是有效的。在本文中,我们使用Guo et al.(2011)半分析模型来分析在宇宙学模拟的背景下,这种假设在什么情况下是有效的。具体来说,我们选择祖先星系在一个恒定的数量密度和比较恒星质量演化的后代在一个恒定的数量密度的演变。从z = 3到z = 0,后代的恒星质量中值增加了4倍(0.6 dex)。常数数密度选择在很宽的数密度范围内将其再现到40%(0.15 dex)以内。我们发现,这种差异主要是由于恒星质量增长率的分散和合并。在对这些过程应用简单的基于观测的校正后,差异减小到12%(0.05 dex)。我们的结论是,数密度选择可以用来预测高红移祖先星系的中位数后代质量。在这项研究中的主要不确定性是,半解析模型不再现所观察到的星系的质量演化,这使得恒星形成,合并和淬火的星系的等级顺序的定量聚集效应有点不确定。

英文摘要:

A central challenge in observational studies of galaxy formation is how to associate progenitor galaxies with their descendants at lower redshifts. One promising approach is to link galaxies at fixed number density, rather than fixed luminosity or mass. This method is effective if stellar mass rank order is broadly conserved through cosmic time. In this paper, we use the Guo et al. (2011) semi-analytical model to analyze under what circumstances this assumption is valid in the context of a cosmological simulation. Specifically, we select progenitor galaxies at a constant number density and compare the stellar mass evolution of their descendants to the evolution at a constant number density. The median stellar mass of the descendants increases by a factor of four (0.6 dex) from z = 3 to z = 0. Constant number density selection reproduces this to within 40% (0.15 dex) over a wide range of number densities. We show that the discrepancy primarily results from scatter in the stellar mass growth rates and merging. After applying simple, observationally-based corrections for these processes, the discrepancy is reduced to 12% (0.05 dex). We conclude that number density selection can be used to predict the median descendant mass of high-redshift progenitor galaxies. The main uncertainty in this study is that semi-analytical models do not reproduce the observed mass evolution of galaxies, which makes the quantitative aggregate effects of star formation, merging, and quenching on the rank order of galaxies somewhat uncertain.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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