A New World Class Infrared Spectrometer for Fundamental Atomic Data for Astrophysics

JWST、ELT、VLT、HST、Keck II、Subaru、UKIRT等地面和天基望远镜正在以前所未有的分辨率记录红外(IR)、可见光(UV)和紫外线(UV)区域的现代天文光谱。对这些数十亿磅仪器记录的光谱进行分析，需要实验室原子数据至少具有匹配的准确性和完整性。然而，对于许多元素和电离状态，现有的原子数据可以追溯到50多年前，基于光栅甚至棱镜光谱仪。自那以后，光谱学技术有了巨大的进步，但产生新的高分辨率、高精度原子数据所需的大规模工作意味着，原子数据库已经落后于天体物理学和天文学领域的需求。在许多情况下，为了明确识别天体物理光谱中感兴趣的所有特征和对天文光谱进行有意义的解释，需要对原子数据的精度进行数量级的改进。理论上不可能以足够的精度计算原子数据来分析高分辨率的天体物理光谱，因此实验光谱学是产生必要精度的原子数据的唯一方法。帝国理工学院光谱组在使用傅立叶变换(FT)光谱学显著改善原子数据方面有着良好的记录。此前，我们的工作集中在可见光和紫外光谱区域，使用我们创纪录的真空UV(VUV)FT光谱仪测量光谱。这笔赠款的资本资金将使我们能够通过增加一台专为红外光谱区域量身定做的世界级高分辨率FT光谱仪来提高我们在红外(IR)领域的能力。对我们设施的这一重要补充，与我们现有的独特的可见光-紫外线FT光谱仪相结合，意味着我们将能够研究整个IR-可见光-UV区域内具有天体物理意义的重要元素的高分辨率光谱。光谱覆盖范围扩大的时机正值红外对天文学家的重要性极大地增长之际，随着新的望远镜，如JWST，在红外区域发射了前所未有的能力。我们将专注于在波长精度、原子能级、对数(Gf)S(确定天体中元素的化学丰度所需的跃迁概率)以及同位素和超精细结构(准确地模拟谱线并再次获得可靠的丰度估计所需的)方面至少提高数量级的测量。与过去使用的最好的光栅光谱仪相比，FT光谱仪具有更高的分辨率，提供的波长和能级精度至少为108%，对数(火焰杯)S的精度为几分之一，并解决了同位素和超精细结构等线宽效应。我们的原子数据与STFC挑战赛的许多问题有关，例如：“恒星和星系是如何演化的？”“太阳和其他恒星是如何工作的，是什么驱动了它们的变异性？”以及“太阳和其他恒星对当地环境有什么影响？”ICL光谱组产生的所有新的实验室原子数据都被纳入原子数据库和恒星模型大气代码，使世界各地的天文学家和英国的天文学家受益。新的红外光谱仪将使我们的集团继续进行世界领先的研究，进入红外天文发现的新时代。我们的目标是，我们向天文学界提供的新的实验室原子数据意味着，对昂贵获得的现代天体物理光谱的分析将不再受到分析中使用的原子数据的质量和数量的限制。

Modern astronomical spectra are being recorded at unprecedented resolutions in the infrared (IR), visible and ultraviolet (UV) regions by both ground- and space-based telescopes including JWST, ELT, VLT, HST, Keck II, Subaru, UKIRT. The analysis of the spectra recorded by these multi-billion-pound instruments requires laboratory atomic data of at least matching accuracy and completeness. However, for many elements and ionisation states, the existing atomic data date back over 50 years, based on grating and even prism spectrometers. Spectroscopy techniques have improved enormously since then, but the large-scale effort needed to produce new high-resolution, high-accuracy atomic data has meant that the atomic database has lagged behind the needs of the astrophysics and astronomy communities. In many cases, order-of-magnitude improvements in accuracy of atomic data are required for unambiguous identification of all features of interest in an astrophysical spectrum and meaningful interpretation of the astronomical spectra. It is not possible to theoretically calculate atomic data with sufficient precision for analyses of high-resolution astrophysical spectra, and so experimental spectroscopy is the only method to generate atomic data of the necessary accuracy. The Imperial College Spectroscopy Group has a strong track record in significantly improving atomic data with Fourier Transform (FT) spectroscopy. Previously, our work was focussed on the visible and UV spectral regions, with spectra measured using our record-holding vacuum UV (VUV) FT spectrometer. The capital funding of this grant will enable us to increase our capabilities into the infrared (IR) through the addition of a world-class, high-resolution FT spectrometer tailored to the IR spectral region. This vital addition to our facility, in combination with our existing unique visible-ultraviolet FT spectrometer, means that we will be able to study high-resolution spectra of astrophysically important elements across the entire IR-visible-UV region. The timing of this increase in spectral coverage has come just as the IR is growing tremendously in importance for astronomers, with new telescopes, such as the JWST, launched with unprecedented capabilities in the IR region.We will focus on measurements leading to at least order-of-magnitude improvements in wavelength accuracy, atomic energy levels, log(gf)s (transition probabilities, needed for determining chemical abundances of elements in astrophysical objects), and isotope and hyperfine structure (needed to model lines accurately and, again, obtain reliable abundance estimates). The much greater resolution of FT spectroscopy, compared to the best grating spectrometers used in the past, provides wavelengths and energy levels accurate to at least parts in 108, log(gf)s accurate to a few percent, and resolved line broadening effects such as isotope and hyperfine structure. Our atomic data are relevant to many STFC Challenge questions such as: "How do stars and galaxies evolve?", "How does the Sun and other stars work and what drives their variability?" and "What effects do the Sun and other stars have on their local environment?". All the new laboratory atomic data produced by the ICL Spectroscopy Group is incorporated into atomic databases and stellar model atmosphere codes, benefiting astronomers worldwide in addition to those in the UK. The new IR spectrometer will allow our Group to continue our world leading research into the new era of IR astronomical discoveries. Our aim is that the new laboratory atomic data we provide to the astronomical community means that analyses of expensively obtained modern astrophysical spectra will no longer be limited by the quality and quantity of atomic data used in their analyses.