arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2101.11643astro-ph.SRastro-ph.GA
收藏

用球状星团星的APOGEE观测探测3D和NLTE模型

Probing 3D and NLTE models using APOGEE observations of globular cluster stars

T. Masseron, Y. Osorio, D. A. García-Hernández, C. Allende Prieto, O. Zamora, Sz. Mészáros

备注：
13 pages, 9 figures, accepted in A&A
发表信息：
A&A 647, A24 (2021)
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

已知流体动力学（或3D）和非局部热力学平衡（NLTE）效应会影响丰度分析。然而，3D和NLTE模式的观测丰度测试非常少。我们开发了一种新的方法来测试3D和NLTE模型的丰度预测，利用大型光谱调查数据。我们使用的阿帕奇点天文台星系演化实验（APOGEE）光谱（H波段）与布鲁塞尔自动代码表征高精度光谱（BACCHUS）的逐线分析。我们计算了APOGEE巡天中大量球状星团K巨星的Mg、Si、Ca和Fe的逐线丰度。我们将这种逐行分析与NLTE和3D预测进行比较。虽然1D-NLTE模型提供了正确方向的修正，但不同模型之间存在定量差异。我们观察到一个更好的协议与数据的模型，包括可靠的碰撞截面。在LTE中计算3D光谱时，数据和模型之间的一致性并不总是令人满意的。然而，我们注意到，为了公平的比较，3D校正应该用自洽导出的恒星参数来计算，而不是用具有相同恒星参数的1D模型。最后，我们专注于3D和NLTE的影响Fe线在H波段，在那里我们观察到一个系统的差异丰度相对于从光学值。我们的结果表明，从H带获得的金属丰度是更准确的贫金属巨星。需要进行更多的原子数据和扩展的自洽3D-NLTE计算。我们开发的用于测试3D和NLTE模型的方法可以扩展到其他线路和元素，特别适合大型光谱调查。

英文摘要：

Hydrodynamical (or 3D) and non-local thermodynamic equilibrium (NLTE) effects are known to affect abundance analyses. However, there are very few observational abundance testsof 3D and NLTE models. We developed a new way of testing the abundance predictions of 3D and NLTE models, taking advantage of large spectroscopic survey data. We use a line-by-line analysis of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra (H band) with the Brussels Automatic Code for Characterizing High accUracy Spectra (BACCHUS). We compute line-by-line abundances of Mg, Si, Ca, and Fe for a large number of globular cluster K giants in the APOGEE survey. We compare this line-by-line analysis against NLTE and 3D predictions. While the 1D-NLTE models provide corrections in the right direction, there are quantitative discrepancies between different models. We observe a better agreement with the data for the models including reliable collisional cross-sections. The agreement between data and models is not always satisfactory when the 3D spectra are computed in LTE. However, we note that for a fair comparison, 3D corrections should be computed with self-consistently derived stellar parameters, and not on 1D models with identical stellar parameters. Finally, we focus on 3D and NLTE effects on Fe lines in the H band, where we observe a systematic difference in abundance relative to the value from the optical. Our results suggest that the metallicities obtained from the H band are more accurate in metal-poor giants. More atomic data and extended self-consistent 3D-NLTE computations need to be made. The method we have developed for testing 3D and NLTE models could be extended to other lines and elements, and is particularly suited for large spectroscopic surveys.

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。

↑