Kinematics and Abundances of the Galactic and M31 Bulges

加州大学洛杉矶分校的R. Michael Rich博士将对银河系凸起进行大规模的径向速度研究，使用从2微米全天成像调查（2MASS）中选择的M巨星，并使用Cerro Tololo美洲天文台的Hydra多光纤光谱仪进行观测。研究人员已经证明，M巨星是非常好的运动学探测器，可以在整个银河系凸起的区域进行研究，即使是在高灭绝区域；10,000径向速度的最终样本比以前的研究大了十倍。里奇博士开发了一种技术，可以精确到3公里/秒的径向速度测量，如果存在的话，可以发现凸起的冷运动特征。将得到的经度-速度图、小轴旋转曲线和其他速度数据与银河系凸起/棒状星系的自洽模型进行比较，将有助于深入了解银河系凸起的形成。此外，里奇博士还将利用红外光谱技术获得银河系和M31凸起处恒星的详细丰度。对于银河系凸起，他将使用凯克天文台的NIRSPEC梯级光谱仪观察至少150颗恒星，距离核心从30到300 pc不等。这个项目将把详细的丰度测量扩展到银河系靠近核心、被尘埃遮蔽的区域。丰度梯度的存在与否限制了棒状星系长期演化的模型，而成分（如氧丰度）的测量可以限制形成的时间尺度和原始恒星群的初始质量函数。里奇将通过支持一名正在进行论文的博士生，以及一名本科生和一名博士后科学家通过该项目进行的研究，为培养下一代天文学家做出贡献。银河系膨胀径向速度调查和由此产生的模型将提供给海登天文馆，该天文馆正在建立一个虚拟的银河系，公众可以在模拟飞行中观察到，他将探索数据的其他可视化方式，将结果带给公众。大约10000颗恒星的光谱和径向速度的整个数据库将提供给天文学界。

Dr. R. Michael Rich, of the University of California - Los Angeles, will undertake a large scale radial velocity study of the Galactic bulge using M giants selected from the Two Micron All-sky Imaging Survey (2MASS) and observed using the Hydra multifiber spectrograph at Cerro Tololo Inter-American Observatory. The investigator has shown that the M giants make excellent kinematic probes that can be studied over the entirety of the Galactic bulge, even in high extinction regions; the ultimate sample of 10,000 radial velocities is a factor of ten greater than previous studies. Dr. Rich has developed techniques that give a precision of 3 km/s for radial velocity measurements, making it possible to discover cold kinematic features in the bulge, if present. Comparison of the resulting longitude-velocity diagrams, minor axis rotation curves, and other velocity data with self-consistent models of the Galactic bulge/bar, will allow for insight into the formation of the Galactic bulge. In addition, Dr. Rich will obtain detailed abundances for stars in the bulges of the Milky Way and M31 using infrared spectroscopy. For the Milky Way bulge, he will observe at least 150 stars ranging from 30 to 300 pc from the nucleus using the NIRSPEC echelle spectrograph at the Keck observatory. This program will extend detailed abundance measurements into regions of the Galaxy that are near the nucleus and are obscured by dust. The presence or absence of an abundance gradient constrains models of secular evolution of the bar, while measurements of composition (e.g. oxygen abundance) can constrain the formation timescale and the initial mass function of the primordial stellar population.Dr. Rich will contribute to the training of the next generation of astronomers by supporting a Ph.D. student whose thesis is in progress and also research by an undergraduate student and a postdoctoral scientist through this program. The Galactic bulge radial velocity survey and the resulting models will be made available to the Hayden Planetarium, which is building a virtual Milky Way Galaxy that can be observed by the public in a simulated fly-through, and he will explore other visualizations of the data to bring the results to the public. The entire database of ~10,000 stars with spectroscopy and radial velocities will be made available to the astronomical community.