Collaborative Research: Discovery and Analysis of Carbon-Enhanced Stars in SDSS-I and SDSS-II

Gillian Knapp博士（普林斯顿大学）、Timothy Beers博士（密歇根州立大学）和Jennifer Johnson博士（俄亥俄州立大学）将根据斯隆数字巡天（SDSS）获得的中分辨率恒星光谱和宽带ugriz光度法，识别和分析银河系中多达数千颗碳增强恒星。这些数据将使这些研究人员能够得出样本中所有恒星的[Fe/H]和[C/Fe]的估计。精确的径向速度也将使对这些恒星的运动学的详细研究成为可能。这些数据将用于约束(1)恒星之间碳增强的频率作为金属丰度下降的函数，这提供了关于早期恒星初始质量函数性质的信息；(2)低金属丰度恒星之间碳增强的分布-例如，它是连续的还是多模态的；(3)碳增强的，金属贫乏的恒星分为（至少）目前公认的两大类。根据与s工艺生产相关的强钡和强锶特征的检测（或不检测），那些显示出s工艺元素存在的元素和那些不存在的元素。这项研究的结果将对天文学、核物理学和化学领域的广泛研究活动产生影响，因为对元素的天体物理起源的了解为理解银河系的化学演化提供了基础，同时也为中子捕获过程的本质的详细研究提供了基础，这是核物理学界非常感兴趣的。这项研究将为天文学和核物理领域的研究生和本科生提供培训机会，并将成为SDSS-II正在进行的广泛教育和推广计划的一部分。

Dr. Gillian Knapp (Princeton University), Dr. Timothy Beers (Michigan State University), & Dr. Jennifer Johnson (Ohio State University), will identify and analyze up to several thousand carbon-enhanced stars in the Milky Way galaxy, based on medium-resolution stellar spectroscopy and broadband ugriz photometry obtained with the Sloan Digital Sky Survey (SDSS). These data will allow these investigators to derive estimates of both [Fe/H] and [C/Fe] for all stars in this sample. Accurate radial velocities will also enable detailed investigations of the kinematics of these stars. These data will be used to constrain (1) the frequency of carbon enhancement among stars as a function of declining metallicity, which provides information on the nature of the initial mass function for early-generation stars, (2) the distribution of carbon enhancement among low-metallicity stars - e.g., whether it is continuous or multi-modal, and (3) the separation of carbon-enhanced, metal-poor stars into (at least) the two main categories that are presently recognized, those that exhibit the presence of s-process elements, and those that do not, based on the detection (or not) of the strong barium and strontium features that are associated with production in the s-process. The results of this research will have impact on a wide range of research activities in astronomy, nuclear physics, and chemistry, since knowledge of the astrophysical origins of the elements provides the basis for understanding the chemical evolution of the Milky Way, as well as for detailed investigations of the nature of neutron-capture processes, which are of great interest to the nuclear physics community. This research will provide opportunities for the training of graduate and undergraduate students in the areas of both astronomy and nuclear physics, and will become part of the extensive education and outreach program being undertaken by SDSS-II.