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arXiv 1201.1012astro-ph.CO
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光谱能量分布拟合的调查设计:Fisher矩阵法

Survey design for Spectral Energy Distribution fitting: a Fisher Matrix approach

Viviana Acquaviva, Eric Gawiser, Steven J. Bickerton, Norman A. Grogin, Yicheng Guo, Seong-Kook Lee

摘要:

星系的光谱能量分布(SED)包含了星系物理性质的信息,为了通过SED拟合测量这些性质,需要多波长观测。在规划这些调查时,优化资源至关重要。Fisher矩阵形式可用于快速确定最佳实验设置,以实现对SED拟合参数的所需约束。然而,由于它依赖于高斯似然函数的假设,因此通常不如其他较慢的技术准确,这些技术从模型和数据之间的直接比较中重建概率分布函数(PDF)。我们比较了SED拟合参数的Fisher矩阵预测的不确定性使用更彻底的PDF拟合技术。我们使用模拟光谱和真实数据,并考虑了大量的各种不同的目标星系的红移,质量,年龄,恒星形成的历史,尘埃含量和波长覆盖。我们发现,在绝大多数情况下(~ 90%),这两种方法报告的不确定性在两个因素内一致。如果年龄测定是不确定的,在PDF拟合中使用的高帽年龄先验,以防止每个星系比宇宙更老,需要在Fisher矩阵中加入,至少近似地,然后才能正确地比较两种方法。我们的结论是,费歇尔矩阵是一个有用的工具,天文调查设计。

英文摘要:

The spectral energy distribution (SED) of a galaxy contains information on the galaxy's physical properties, and multi-wavelength observations are needed in order to measure these properties via SED fitting. In planning these surveys, optimization of the resources is essential. The Fisher Matrix formalism can be used to quickly determine the best possible experimental setup to achieve the desired constraints on the SED fitting parameters. However, because it relies on the assumption of a Gaussian likelihood function, it is in general less accurate than other slower techniques that reconstruct the probability distribution function (PDF) from the direct comparison between models and data. We compare the uncertainties on SED fitting parameters predicted by the Fisher Matrix to the ones obtained using the more thorough PDF fitting techniques. We use both simulated spectra and real data, and consider a large variety of target galaxies differing in redshift, mass, age, star formation history, dust content, and wavelength coverage. We find that the uncertainties reported by the two methods agree within a factor of two in the vast majority (~ 90%) of cases. If the age determination is uncertain, the top-hat prior in age used in PDF fitting to prevent each galaxy from being older than the Universe needs to be incorporated in the Fisher Matrix, at least approximately, before the two methods can be properly compared. We conclude that the Fisher Matrix is a useful tool for astronomical survey design.

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