恒星族群合成选择对基于前向建模的红移分布估计的影响
Impact of stellar population synthesis choices on forward modelling-based redshift distribution estimates
AI总结：
本文通过 Prospector beta 基准模型与 SOM 层析分箱开展敏感性分析，量化不同 SPS/SED 建模选择对红移分布均值和弥散的影响，发现 IMF、AGN、气体物理和衰减定律导致的偏差超过 LSST、Euclid 等 Stage IV 巡天要求。
摘要：
星系巡天的前向建模近来引起了广泛兴趣，被视为使第四阶段（stage IV）巡天的红移分布估计达到所需精度的主要方法之一。前向建模星系巡天的一个关键方面，是通过恒星族群合成（SPS）代码（例如 FSPS）建立从星系族群模型抽取的物理属性与内禀光谱能量分布（SED）之间的联系。然而，SPS 需要对星系组成成分作出大量详细假设，而这些假设的模型选择或参数值目前仍不确定。在本研究中，我们开展了一项敏感性研究，考察 SED 建模选择的变化对层析星系红移分布的均值和弥散的影响。我们采用 Prospector beta 模型作为基准输入星系族群模型，并使用其 SPS 参数构建基准星系样本的 9 个波段星等。随后，我们每次改变一项 SED 建模选择，以构建不同的星系星等样本。我们使用 SOM 方法对这些星系样本的颜色–红移关系进行建模。我们根据星系在观测坐标系中的颜色将其分配到 SOM 单元中，并利用其单元归属构建颜色选择的层析分箱。最后，我们将每个变体的分箱红移分布与针对基准模型得到的估计进行比较。我们发现，与 IMF、AGN、气体物理以及衰减定律相关的 SED 组成成分，会使层析红移分布的均值和弥散相对于采用基准模型估计的结果产生显著偏差。无论采用何种基于恒星质量函数的再加权策略，层析红移分布均值和弥散中的偏差都大于下一代第四阶段星系巡天（例如 LSST 和 Euclid）所设定的精度要求。
英文摘要：
The forward modelling of galaxy surveys has recently gathered interest as one of the primary methods to achieve the required precision on the estimate of the redshift distributions for stage IV surveys. One of the key aspects of forward modelling a galaxy survey is the connection between the physical properties drawn from a galaxy population model and the intrinsic SEDs, achieved through SPS codes (e.g. FSPS). However, SPS requires a large number of detailed assumptions on the constituents of galaxies, for which the model choice or parameter values are currently uncertain. In this work, we perform a sensitivity study of the impact that the variations of the SED modelling choices have on the mean and scatter of the tomographic galaxy redshift distributions. We assumed the Prospector beta model as the fiducial input galaxy population model and used its SPS parameters to build 9 bands magnitudes of a fiducial sample of galaxies. We then built samples of galaxy magnitudes by varying one SED modelling choice at a time. We modelled the colour redshift relation of these galaxy samples using the SOM approach. We placed galaxies in the SOM cells according to their observed frame colours and used their cell assignment to build colour selected tomographic bins. Finally, we compared each variant's binned redshift distributions against the estimates obtained for the fiducial model. We find that the SED components related to the IMF, AGNs, gas physics, and the attenuation law substantially bias the mean and the scatter of the tomographic redshift distributions with respect to those estimated with the fiducial model. Regardless of the applied stellar mass function based re-weighting strategy, the bias in the mean and the scatter of the tomographic redshift distributions are greater than the precision requirements set by next-generation Stage IV galaxy surveys, such as LSST and Euclid.
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