Stellar metallicity from optical and UV spectral indices: Test case for WEAVE-StePS
Stellar metallicity from optical and UV spectral indices: Test case for WEAVE-StePS
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来自光学和紫外光谱指数的恒星金属丰度：WEAVE-StepPS 测试用例
DOI：
10.1051/0004-6361/202346563
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发表时间：
2023
影响因子：
6.5
通讯作者：
Ditrani F
中科院分区：
文献类型：
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作者：
Ditrani F
即将到来的四米级望远镜上的新一代光谱仪，凭借其巨大的多路复用能力，出色的光谱分辨率和前所未有的波长覆盖范围，将为数千个星系提供高质量的光谱。这些数据将使我们能够检查在中等红移，一个时代，仍然是未探索的大和深调查的恒星布居properties.AimsWe评估我们的能力，检索星系中的平均恒星金属丰度在不同的红移和信噪比（S/N），同时利用紫外线（UV）和光学休息-帧波长覆盖范围。方法这项工作是基于恒星种群的光谱模板的综合库，覆盖了广泛的年龄和金属量值，并假设各种星星形成历史而建立，以覆盖具有不同化学富集历史和尘埃衰减的可观测参数空间。我们考虑到可能的观测误差，模拟现实的观测大样本的星系进行了与WEAVE在theWilliam Herschel望远镜在不同的红移和S/N值。我们在模拟光谱和比较库上测量了所有可用和可靠的指数。然后，我们采用贝叶斯方法比较两组测量，以获得恒星金属丰度的概率分布与准确估计的不确定性。ResultsThe光谱指数的分析表明，如何一些中紫外线指数，如BL 3580和Fe 3619，可以提供可靠的约束恒星金属丰度，沿着与光学指标。模拟观测的分析表明，即使在S/N= 10时，金属丰度也可以在0.3 dex以内导出，特别是对于年龄大于2 Gyr的恒星。S/N值在估计金属丰度的不确定性中起着至关重要的作用，因此，S/N= 10和S/N= 30之间的差异相当大，在后一种情况下的不确定性约为0.15 dex。相反，从S/N= 30移动到S/N= 50，金属丰度测量的不确定性的改善几乎可以忽略不计。我们的结果是在良好的协议与其他理论和观测工作在文献中，并显示如何紫外指示剂，再加上经典的光学，可以是有利的约束metallicits.ConclusionsWe表明，一个良好的精度可以达到光谱测量的恒星金属丰度的星系在中等红移，即使在低的S/N，当大量的指数可以采用，包括一些紫外线指数。这对于即将进行的调查是非常有希望的，新的，高度多路复用的，大视场摄谱仪，如WEAVE和4 MOST的StepPS，它将提供数千个星系的光谱，覆盖大光谱范围（在观测帧中在3600和9000之间），相对较高的S/N（>10 <$−1）。
ContextThe upcoming generation of optical spectrographs on four meter-class telescopes, with their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage, will provide high-quality spectra for thousands of galaxies. These data will allow us to examine of the stellar population properties at intermediate redshift, an epoch that remains unexplored by large and deep surveys.AimsWe assess our capability to retrieve the mean stellar metallicity in galaxies at different redshifts and signal-to-noise ratios (S/N), while simultaneously exploiting the ultraviolet (UV) and optical rest-frame wavelength coverage.MethodsThe work is based on a comprehensive library of spectral templates of stellar populations, covering a wide range of age and metallicity values and built assuming various star formation histories, to cover an observable parameter space with diverse chemical enrichment histories and dust attenuation. We took into account possible observational errors, simulating realistic observations of a large sample of galaxies carried out with WEAVE at theWilliam HerschelTelescope at different redshifts and S/N values. We measured all the available and reliable indices on the simulated spectra and on the comparison library. We then adopted a Bayesian approach to compare the two sets of measurements in order to obtain the probability distribution of stellar metallicity with an accurate estimate of the uncertainties.ResultsThe analysis of the spectral indices has shown how some mid-UV indices, such as BL3580 and Fe3619, can provide reliable constraints on stellar metallicity, along with optical indicators. The analysis of the mock observations has shown that even atS/N= 10, the metallicity can be derived within 0.3 dex, in particular, for stellar populations older than 2 Gyr. The S/N value plays a crucial role in the uncertainty of the estimated metallicity and so, the differences betweenS/N= 10 andS/N= 30 are quite large, with uncertainties of ~0.15 dex in the latter case. On the contrary, moving fromS/N= 30 toS/N= 50, the improvement on the uncertainty of the metallicity measurements is almost negligible. Our results are in good agreement with other theoretical and observational works in the literature and show how the UV indicators, coupled with classic optical ones, can be advantageous in constraining metallicities.ConclusionsWe demonstrate that a good accuracy can be reached on the spectroscopic measurements of the stellar metallicity of galaxies at intermediate redshift, even at low S/N, when a large number of indices can be employed, including some UV indices. This is very promising for the upcoming surveys carried out with new, highly multiplexed, large-field spectrographs, such as StePS at the WEAVE and 4MOST, which will provide spectra of thousands of galaxies covering large spectral ranges (between 3600 and 9000 Å in the observed frame) at relatively high S/N (>10 Å−1).