How to Measure Galaxy Star Formation Histories. I. Parametric Models
How to Measure Galaxy Star Formation Histories. I. Parametric Models
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DOI：
10.3847/1538-4357/ab04a2
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发表时间：
2019-03-01
影响因子：
4.9
通讯作者：
Conroy, Charlie
中科院分区：
文献类型：
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作者：
Carnall, Adam C.;Leja, Joel;Conroy, Charlie
星系恒星形成历史（SFHs）的参数模型被广泛使用，尽管已知它们对物理参数施加了很强的先验。这对测量星系恒星质量函数、恒星形成速率密度（SFRD）和恒星形成主序（SFMS）产生了影响。我们使用BAGPIPES研究了指数下降、延迟指数下降、对数正态和双幂律SFH模型的影响。我们证明，这些模型中的每一个都对特定的恒星形成率（SFRs）施加了很强的先验，可能会使SFRs产生偏差，并且还对年轻的恒星群施加了很强的先验偏好。我们发现，高质量模拟光度法得出的恒星质量、SFR和质量加权年龄分别随SFH模型的选择而变化至少0.1、0.3和0.2个指数。然而，相对于真实值的偏差更多地取决于真实的SFH形状，而不是模型的选择。我们还证明了光度数据不能区分SFH模型，这意味着进行独立测试以找到动机良好的先验是很重要的。我们最终将来自星系和质量集合（GAMA）调查的低红移、体积完整的星系样本与每个模型相匹配。我们证明了我们的恒星质量和srr在红移z接近0.05时与其他分析是一致的。然而，我们推断出的宇宙sfrd峰值在z接近0.4处，比直接观测结果晚了大约6 Gyr，这意味着我们的质量加权年龄被严重低估了。这使得使用参数SFH模型来理解星系中的质量组装具有挑战性。在另一篇论文中，我们考虑了非参数SFH模型。
Parametric models for galaxy star formation histories (SFHs) are widely used, though they are known to impose strong priors on physical parameters. This has consequences for measurements of the galaxy stellar-mass function, star formation rate density (SFRD), and star-forming main sequence (SFMS). We investigate the effects of the exponentially declining, delayed exponentially declining, lognormal, and double power-law SFH models using BAGPIPES. We demonstrate that each of these models imposes strong priors on specific star formation rates (SFRs), potentially biasing the SFMS, and also imposes a strong prior preference for young stellar populations. We show that stellar mass, SFR, and mass-weighted age inferences from high-quality mock photometry vary with the choice of SFH model by at least 0.1, 0.3, and 0.2 dex, respectively. However, the biases with respect to the true values depend more on the true SFH shape than the choice of model. We also demonstrate that photometric data cannot discriminate between SFH models, meaning that it is important to perform independent tests to find well-motivated priors. We finally fit a low-redshift, volume-complete sample of galaxies from the Galaxy and Mass Assembly (GAMA) Survey with each model. We demonstrate that our stellar masses and SFRs at redshift z similar to 0.05 are consistent with other analyses. However, our inferred cosmic SFRDs peak at z similar to 0.4, approximately 6 Gyr later than direct observations suggest, meaning that our mass-weighted ages are significantly underestimated. This makes the use of parametric SFH models for understanding mass assembly in galaxies challenging. In a companion paper, we consider nonparametric SFH models.