Infrared Beacons in the Universe - J Band Spectroscopy of Red Supergiants and the Chemical Composition of Star Forming Galaxies

确定星系的化学成分对于理解它们的形成和演化至关重要。标准技术，利用漫射星际气体（特别是HII区域）的发射谱线，受到巨大的和难以理解的系统不确定性的困扰。该项目将开发一种新的、潜在的革命性方法，该方法基于单个红超巨星的近红外光谱。这些恒星的输出在j波段达到峰值，那里的光谱中有丰富的原子谱线。新的10米级望远镜上的多目标红外光谱仪将能够获得足够的分辨率，以获得距离为10百万秒差距的精确丰度。该项目的目的是开发、验证和利用这项新技术，分几个步骤：(1)该技术将在银河系和麦哲伦星云中进行测试，与使用HII区域和蓝超巨星光谱的互补技术进行对比；(2)对金属丰度极低的本星系群（NGC 3109、WLM、IC 1613）和螺旋星系M31、M33进行研究，并与蓝超巨星的结果进行比较；(3)该技术将被应用于本星系群以外的螺旋星系（NGC 300, NGC 2403, M81），直到几个百万秒差距。将获得精确的丰度和丰度梯度，允许对恒星形成星系的演化状态和历史进行约束，以及对H II区域技术的可靠性进行评估。该方法还将扩展到超级星团，其中包含许多控制j波段通量的红超巨星，并且可能在更大的距离上作为宇宙丰度指标有用。最终，这项技术可能会被下一代大型望远镜所充分利用，实现100兆秒差距的丰度测量，这是当地宇宙的相当大的体积。该项目将支持一名研究生的工作，他将参与国际合作。研究结果将纳入首席研究员开展的教育和公众外展活动。

Determining the chemical composition of galaxies is crucial for understanding their formation and evolution. Standard techniques, utilizing emission line spectra of the diffuse interstellar gas (specifically HII regions), is plagued by large and poorly understood systematic uncertainties. This project will develop a new, and potentially transformative, approach based on near-infrared spectroscopy of individual red supergiant stars. The output of these stars peaks in the J-band, where the spectra are rich in atomic lines. New multi-object infrared spectrographs on 10-meter-class telescopes will be able to obtain sufficient resolution to derive accurate abundances to distances of 10 megaparsecs. The purpose of this project is to develop, validate and exploit this new technique, in several steps: (1) The technique will be tested in the Milky Way and the Magellanic Clouds, against complementary techniques using HII region and blue supergiant star spectra; (2) Local Group galaxies of extremely low metallicity (NGC 3109, WLM, IC 1613) and the spirals M31 and M33 will be studied and compared with results from blue supergiants; (3) the technique will be applied to spiral galaxies beyond the Local Group out to a few megaparsecs (NGC 300, NGC 2403, M81). Accurate abundances and abundance gradients will be obtained, allowing constraints on the evolutionary states and histories of star forming galaxies, as well as an assessment of the reliability of H II region techniques. The method will also be extended to super-star clusters, which contain many dozens of red supergiants dominating the J-band flux, and which may be useful as cosmological abundance indicators at even larger distances. Eventually, this technique may be best exploited by the next generation of large telescopes, achieving abundance measurements out to 100 megaparsecs, a substantial volume of the local universe. The project will support the work of one graduate student, who will participate in international collaborations. Results will be incorporated into education and public outreach activities conducted by the Principal Investigator.