The Outer Half of Disk Galaxies

扎里茨基博士将使用大型双筒望远镜的深度光学成像和光谱学来研究星系盘外部的恒星含量、历史和运动。长期以来，人们一直认为这些区域含有气体，但直到最近，人们还认为它们不会产生新的恒星。利用蓝光下的深部图像将绘制出一簇簇新恒星，以研究外星系恒星诞生的历史，并找到恒星盘的真实边缘。星团的运动将从它们的谱线的多普勒移中测量出来。平均运动将显示银河系外部围绕其中心旋转的速度，外盘的质量密度可以从单个恒星团的运动偏离该平均值的方式来推断。扎里茨基博士将利用他的结果来测试星系演化模型中的关键概念，例如，薄盘能否在大型星系的反复合并中存活下来；标度关系的紧密性对星系盘的发展意味着什么；以及盘的大小如何与原星系的角动量分布有关。这项提议将为研究生的培训提供资金。扎里茨基博士将利用他的深星系图像，为他的本科生观测天文学课程、他提议在2010年开设的梵蒂冈暑期学校以及计划于2009年冬季在加纳举办的海外留学课程开发实验室练习。这些实验室还将通过互联网提供。

Dr Zaritsky will use deep optical imaging and spectroscopy with the Large Binocular Telescope to study the stellar content, history, and motions in the outer parts of galaxy disks. These regions were long known to contain gas, but until recently were thought to be making no new stars. Clumps of new stars will be mapped out using deep images in blue light, to investigate the history of starbirth in the outer galaxy, and find the true edge of the stellar disk. The motions of the stellar clumps will be measured from the Doppler shift of their spectral lines. The averaged motion will show how fast the outer parts of the galaxy rotate about its center, and the mass density of the outer disk can be inferred from the way that the motion of individual clumps of stars deviates from that mean. Dr Zaritsky will use his results to test key concepts in models for galactic evolution, such as whether the thin disks can survive the repeated mergers through which large galaxies are expected to grow; what the tightness of scaling relations implies for the development of galaxy disks; and how disk sizes could be related to the angular momentum distribution of the protogalaxy.This proposal will fund the training of a graduate student. Dr Zaritsky will use his deep galaxy images to develop laboratory exercises for his undergraduate observational astronomy class, a Vatican summer school that he has proposed for 2010, and a Study Abroad course in Ghana scheduled for winter 2009. The labs will also be made available over the internet.