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arXiv 2402.19337astro-ph.IM
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积分场光谱支持大气光学揭示湍流的有限外尺度

Integral field spectroscopy supports atmospheric optics to reveal the finite outer scale of the turbulence

Begoña García-Lorenzo, Donaji Esparza-Arredondo, Jose A. Acosta-Pulido, Julio A. Castro-Almazán

AI总结:

本文提出利用积分场光谱数据估计大气湍流波前外尺度L_0的新方法,并通过MUSE观测验证了Tokovinin解析表达式对图像质量随波长变化的预测能力,同时提供了一种从常规IFS观测中表征L_0和穹顶视宁度的简便途径。

摘要:

空间相干波前外尺度(L_0)表征地球大气中最大湍流涡旋的尺度,决定了地面望远镜捕获光波波前中的低空间频率扰动。本工作的动机是引入一种从受视宁度限制的积分场光谱(IFS)数据中估计 L_0 的新技术。该方法基于有限 L_0 对地面望远镜入瞳所收集光线的影响。我们利用 IFS 的均匀性生成覆盖宽波长范围的带通滤波图像,从而能够评估望远镜焦平面处的图像质量(IQ)。将测量得到的随波长变化的 IQ 变化与 Tokovinin(2002)解析方法的预测进行比较,可以为观测期间占主导地位的 L_0 参数提供有价值的见解。我们将所提出的技术应用于帕拉纳尔天文台获得的 MUSE 宽场模式观测数据。我们的分析成功验证了 Tokovinin 的解析表达式,该表达式结合视宁度(E_0)和 L_0 参数,用于预测地面天文数据中 IQ 随波长的变化。然而,我们观察到 IQ 的测量值与预测值之间存在一些差异,并从估计 E_0 的不确定性和穹顶引起的湍流贡献方面对这些差异进行了分析。本工作构成了在特定 E_0 和有限 L_0 条件下估计地面望远镜焦平面 IQ 的解析表达式的经验验证。此外,我们提供了一种简单的方法,将 L_0 和穹顶视宁度(E_d)作为主要地面天文台常规进行的 IFS 观测的副产品来表征。

英文摘要:

The spatial coherence wavefront outer scale (L_0) characterizes the size of the largest turbulence eddies in Earth's atmosphere, determining low spatial frequency perturbations in the wavefront of the light captured by ground-based telescopes. The motivation of this work is to introduce a novel technique for estimating L_0 from seeing-limited integral field spectroscopic (IFS) data. This approach is based on the impact of a finite L_0 on the light collected by the pupil entrance of a ground-based telescope. We take advantage of the homogeneity of IFS to generate band filter images spanning a wide wavelength range, enabling the assessment of image quality (IQ) at the telescope's focal plane. Comparing the measured wavelength-dependent IQ variation with predictions from Tokovinin (2002) analytical approach offers valuable insights into the prevailing L_0 parameter during the observations. We applied the proposed technique to observations from MUSE in the Wide Field Mode obtained at the Paranal Observatory. Our analysis successfully validates Tokovinin's analytical expression, which combines the seeing (E_0) and the L_0 parameters, to predict the IQ variations with the wavelength in ground-based astronomical data. However, we observed some discrepancies between the measured and predictions of the IQ that are analyzed in terms of uncertainties in the estimated E_0 and dome-induced turbulence contributions. This work constitutes the empirical validation of the analytical expression for estimating IQ at the focal plane of ground-based telescopes under specific E_0 and finite L_0 conditions. Additionally, we provide a simple methodology to characterize the L_0 and dome-seeing (E_d) as by-products of IFS observations routinely conducted at major ground-based astronomical observatories.

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