The Calcium Triplet in the Near Infrared: Its Calibration and Use in Determining the Evolution of the Large Magellanic Cloud

AST-0070985 Tammy Smecker-Hane该提案的目标是：a）获得11个银河系星团中10到20颗红巨星的光谱（在8000埃钙三重态的波长区域），并确定（使用恒星大气）作为金属度指示剂的Ca II三重态的校准。B）获得大麦哲伦星云3个区域中每一个区域的~110颗红巨星的光谱，并应用星系团巨星的校准来确定大麦哲伦星云巨星的金属丰度，从而确定大麦哲伦星云中星星的形成历史。LMC的观测将有助于理解恒星形成历史的局部变化是如何分布的。这反过来将有助于我们理解中等红移星系中的恒星形成。现代天体物理学的基本目标之一是了解星系是如何演化的。一个星系的演化可以通过测量其恒星的化学成分和年龄来确定。在这个项目中，Smecker-Hane教授和合作者将实现两个目标。首先，他们将校准恒星近红外光谱中钙吸收线的深度，作为年龄和化学成分的函数。 他们将把目前的校准扩展到更年轻和更富含金属的恒星，这样钙线就可以用来研究其他星系，这些星系的恒星年龄从20亿到150亿年，化学成分从太阳的1到1/1000。其次，这些研究人员将使用智利Cerro Tololo InterAmerican 4米望远镜，使用这种新的校准来确定大麦哲伦云（LMC）中恒星的化学成分与半径的函数。LMC是一个富含气体的中等质量星系，距离只有16万光年，这使它成为银河系最近的邻居之一。他们将联合收割机的化学成分与哈勃太空望远镜的数据相结合，以准确测量LMC的恒星形成历史。现有的数据表明，大麦哲伦星云在大约30亿到50亿年前经历了一次星星形成的重大爆发，了解爆发的细节-它的强度，持续时间和原因-可以为我们提供关于星星爆发的性质的有价值的线索，这些爆发经常出现在中等红移的暗蓝色星系中。该项目的资金由美国国家科学基金会的星系外天文学宇宙学计划（AST/EXC）提供。

AST-0070985Tammy Smecker-HaneThe goals of this proposal are to: a) Obtain spectra (in the wavelength region of the 8000-Angstrom calcium triplet) of 10 to 20 red giant stars in 11 Galactic clusters and determine (using stellar atmospheres ) the calibration of the CaII triplet as a metallicityindicator. b) Obtain spectra of ~110 Red Giants in each of 3 regions in LMC and apply the calibration from the Galactic cluster giants to determine the LMC giant's metallicity and thus determine the star formation history in the LMC . The LMC observations will aid in understanding how local variations in star-formation history are distributed. This, in turn, will help us to understand star-formation in intermediate redshift galaxies.One of the fundamental goals of modern astrophysics is to understand how galaxies have evolved. A galaxy's evolution can be determined by measuring the chemical compositions and ages of its stars. In this project, Professor Smecker-Hane and collaborators will accomplish two goals. First, they will calibrate the depth of calcium absorption lines in the near-infrared spectra of stars as a function of age and chemical composition. They will extend the current calibration to younger and more metal-rich stars so the calcium lines can be used to investigate other galaxies which have stars with ages from 2 to 15 billion years and chemical compositions from one to one-thousandth of the Sun. Second, these investigators will use this new calibration to determine the chemical composition of stars as a function of radius in the Large Magellanic Cloud (LMC) using Cerro Tololo InterAmerican 4 meter Telescope in Chile. The LMC is a gas-rich, intermediate-mass galaxy with a distance of only 160,000 light years, which makes it one of the Milky Way's nearest neighbors. They will combine the chemical compositions with data from the Hubble Space Telescope in order to accurately measure the LMC's star-formation history. Existing data hints that the LMC experienced a significant burst of star formation approximately 3 to 5 billion years ago, and understanding the details of the burst -- its strength, duration, and cause - can give us valuable clues about the nature of star bursts frequently seen in faint blue galaxies at intermediate redshifts. Funding for this project was provided by the NSF program for ExtragalacticAstronomy & Cosmology (AST/EXC).***