大型恒星光谱巡天中用于丰度测定的谱线自动选择方法
Automatic line selection for abundance determination in large stellar spectroscopic surveys
AI总结：
本研究提出一种自动判定恒星光谱原子谱线纯度与可探测性的方法，可用于光谱仪设置优化和谱线表构建，经WEAVE设置及不同分辨率光谱验证，能为光谱仪效能发挥提供诊断支持。
摘要：
研究背景：新型多目标光谱仪的优化（分辨率、波长范围等）、其配套巡天项目的设置选择，以及相关参数化处理管线，都需要能够估算哪些波长包含有用信息的方法。研究目的：我们提出一种可判定原子谱线实用性（纯度与可探测性）的方法，并展示两项应用：a）通过比较特定设置下的有用谱线数量来优化仪器；b）通过选择在不同信噪比下可探测的、混叠最少的谱线，为特定设置优化谱线表。研究方法：该方法将预先计算的、包含所有元素与分子的合成恒星光谱，与仅包含特定元素谱线的光谱进行比对，随后计算全光谱与单元素光谱的流量比，以此估算谱线纯度。该方法可自动识别三项内容：（i）谱线的中心波长；（ii）基于谱线深度与给定信噪比阈值的可探测性；（iii）基于纯度比的实用性。研究结果：我们对比了WEAVE的三种高分辨率设置（蓝光段：404-465nm，绿光段：473-545nm，红光段：595-685nm），发现绿光+红光的组合设置既能测量更多元素，也包含更多有用谱线，但不同设置下可探测的元素存在差异，我们对此进行了表征。我们还研究了覆盖整个光学波段、分辨率R~20000与R~6000的光谱的性能。在60%的纯度阈值假设下，我们发现高分辨率设置针对所有研究元素都提供了丰富得多的谱线选择，而低分辨率设置即使在更高信噪比下，也会“损失”50%至90%的谱线。研究结论：该方法可为如何聚焦研究重点以充分发挥光谱仪性能提供诊断依据，且易于在未来仪器或需要谱线掩模的处理管线中部署应用。
英文摘要：
*Context: The optimisation of new multiplex spectrographs (resolution, wavelength range,...), their associated surveys (choice of setup), or their parameterisation pipelines require methods that estimate which wavelengths contain useful information. *Aim: We propose a method that establishes the usefulness (purity & detectability) of an atomic line. We show two applications: a) optimising an instrument, by comparing the number of useful lines at a given setup, and b) optimising the line-list for a given setup by choosing the least blended lines detectable at different signal-to-noise ratios. *Method: The method compares pre-computed synthetic stellar spectra containing all of the elements and molecules with spectra containing the lines of specific elements alone. Then, the flux ratios between the full spectrum and the element spectrum are computed to estimate the line purities. The method identifies automatically (i) the line's central wavelength, (ii) its detectability based on its depth and a given S/N threshold and (iii) its usefulness based on the purity ratio. *Results: We compare the three WEAVE high-resolution setups (Blue: 404-465nm, Green: 473-545nm, Red: 595-685nm), and find that the Green+Red setup both allows one to measure more elements and contains more useful lines. However, there is a disparity in terms of which elements are detected, which we characterise. We also study the performances of R~20 000 and R~6000 spectra covering the entire optical range. Assuming a purity threshold of 60%, we find that the HR setup contains a much wealthier selection of lines, for any of the considered elements, whereas the LR has a "loss" of 50 to 90% of the lines even for higher S/N. *Conclusions: The method provides a diagnostic of where to focus to get the most out of a spectrograph, and is easy to implement for future instruments, or for pipelines that require line masks.
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