U.S.-U.K.-Cooperative Research: Structure of Dwarf IrregularGalaxies

该奖项将支持华盛顿大学天文系的Paul Hodge博士和英国爱丁堡皇家天文台的Harvey MacGillivray博士正在进行的合作研究。研究人员提议研究本地矮星不规则星系群的外部结构，特别是NGC6822和IC1613。矮型不规则星系是最常见的空间星系类型之一，但它们的结构，特别是外层区域的结构，仍然相对未被探索。在本星系群中，麦哲伦星云一直是大量结构研究的对象；然而，接下来的两颗矮星(按光度顺序)NGC6822和IC1613却知之甚少。这些星系的外部区域可能会提供关于星系本身遥远过去历史的大量信息，因为它们受到在密度较高的中心区域发现的最近恒星形成事件的影响较小。而且，更重要的是，受外部影响最大的是外部低密度区域，例如与更大质量星系的引力相互作用，或者可能的大质量晕对引力的支持。研究人员建议使用深、宽视场的施密特平板来探索这些星系的外部结构。这些车牌将在爱丁堡用COSMOS机器进行扫描，然后数据将用新的爱丁堡软件处理，该软件开发的目的是即使在非常拥挤的领域也能进行工作。这些恒星将被交叉识别，以建立颜色-星等图，从中减去前景恒星。这将使研究人员能够辨别出距离星系中心不同位置和距离的恒星群。霍奇博士是矮小星系结构方面的顶尖专家。爱丁堡天文学家在从深施密特板块自动计数的恒星分布中提取最完整和可靠的银河系结构科学信息的方法方面拥有多年的经验。他们开发了专门设计的分析技术，以克服由于背景变化和拥挤而导致自动恒星计数中的系统误差的困难。这项研究的结果对于我们理解恒星和星系的演化都将是非常重要的。

This award will support ongoing collaborative research between Dr. Paul Hodge, Department of Astronomy, University of Washington and Dr. Harvey MacGillivray, Royal Observatory, Edinburgh, U.K. The researchers propose to study the outer structure of the local group of dwarf irregular galaxies, especially NGC 6822 and IC 1613. Dwarf irregular galaxies are among the most common type of space galaxies, but their structure, especially in their outer regions, remains relatively unexplored. In the local group, the Magellanic Clouds have been the subject of a large number of structural studies; however the next two dwarfs (in order of luminosity) NGC 6822 and IC 1613 are very poorly understood. The outer reaches of these galaxies are likely to provide considerable information about the distant past history of the galaxies themselves, as they are less affected by the recent star-forming events that are found in the denser, central regions. And, even more important, it is the outer, low-density regions that are most affected by external influences, e.g, gravitational interactions with more massive galaxies or gravitational support by a possible massive halo. The investigators propose to use deep, wide-field Schmidt plates to explore the outer structure of these galaxies. The plates will be scanned in Edinburgh with the COSMOS machine and the data will then be processed with the new Edinburgh software, developed to allow work even in very crowded fields. The stars will be cross-identified to allow construction of color-magnitude diagrams from which foreground stars are subtracted. This will enable the investigators to discern the stellar population at different positions and distances from the center of the galaxies. Dr. Hodge is a leading expert in dwarf galaxy structure. The Edinburgh astronomers have many years experience in methods of extracting the most complete and reliable scientific information on galactic structure from star distributions counted automatically from deep Schmidt plates. They have developed analysis techniques specifically designed to overcome the difficulties that can lead to systematic errors in automated star counting due to background change and crowding. The results of this research will be of great importance for our understanding of both stellar and galaxy evolution.