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arXiv 1802.06197astro-ph.GA
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星系恒星形成率历史的近似:两个例子的性质和应用

Approximations to galaxy star formation rate histories: properties and uses of two examples

J. D. Cohn

摘要:

星系通过许多不同的物理过程、尺度和成分的复杂相互作用而演化。尽管如此,总的趋势往往出现。简化的星系历史模型可以用来寻找和捕捉这种涌现的趋势,从而解释和比较星系形成模型的结果,彼此和自然。在这里,两个近似适用于星系综合恒星形成率的历史,从一个半解析模型嫁接到一个暗物质模拟。对数正态函数形式和主成分分析(PCA)近似的综合恒星形成率的历史相当不错。基于简化的星系晕历史的机器学习在恢复这两种情况方面都取得了一定的成功。拟合的历史给固定时间的恒星形成率有显着的分散从他们真正的固定时间率在最后的时间,特别是静止的和“绿谷”星系,更是如此的PCA拟合。对于将星系划分为具有相似综合历史的亚族,这两种近似方法都优于使用最终恒星质量或特定恒星形成率。模拟中的几个子样本说明了这些简单的参数化如何为不同星系形成样本或更一般的模型之间的比较提供联系点。作为一个附带的结果,模拟星系的晕质量与早期峰值恒星形成率(根据对数正态拟合)位于两个轨道之一。一小部分在恒星形成率达到峰值时具有较低晕质量的星系似乎在它们的晕生长中停滞,即使它们在宿主晕中处于中心位置。

英文摘要:

Galaxies evolve via a complex interaction of numerous different physical processes, scales and components. In spite of this, overall trends often appear. Simplified models for galaxy histories can be used to search for and capture such emergent trends, and thus to interpret and compare results of galaxy formation models to each other and to nature. Here, two approximations are applied to galaxy integrated star formation rate histories, drawn from a semi-analytic model grafted onto a dark matter simulation. Both a lognormal functional form and principal component analysis (PCA) approximate the integrated star formation rate histories fairly well. Machine learning, based upon simplified galaxy halo histories, is somewhat successful at recovering both fits. The fits to the histories give fixed time star formation rates which have notable scatter from their true fixed time rates at final time, especially for quiescent and "green valley" galaxies, and more so for the PCA fit. For classifying galaxies into subfamilies sharing similar integrated histories, both approximations are better than using final stellar mass or specific star formation rate. Several subsamples from the simulation illustrate how these simple parameterizations can provide points of contact for comparisons between different galaxy formation samples, or more generally, models. As a side result, the halo masses of simulated galaxies with early peak star formation rate (according to the lognormal fit) lie on one of two tracks. The small fraction of galaxies with a lower halo mass at peak star formation rate appear to stall in their halo growth, even though they are central in their host halos.

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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