Mapping Microlensing and Stellar Variability in M31

首席研究员和同事们建议研究M31中的微透镜事件，利用该星系中的背景恒星来识别M31本身和我们自己星系中的微透镜。在M31中，透镜事件的发生率预计比在我们的星系或LMC中要高，因为M31的倾角允许我们透过更大的恒星柱密度来观察。除了透镜天体，调查还将发现内在变星（如Mira变星）。当今天体物理学的一个关键问题是，星系中已知的暗物质是由什么组成的。一个关键的线索来自于观测，它表明我们银河系的很大一部分质量可能是由于“大质量，紧凑的光晕物体”（MACHOs），这是一个极具争议和难以理解的解释。这项提议是为了资助一个为期三年的观测项目，涉及我们最近的邻居，仙女座的大星系M31，这将解决星系暗物质的很大一部分是否由晕中的恒星质量物体组成的问题。这些结果可以在竞争的、提出的方法之前得到，并在与我们自己的星系分离的背景下解决当前的困境，表明MACHO晕是否是一种普遍现象。这项提议的研究可以解决银河系调查中关于中央凸起的结构和内容的悬而未决的问题，也可以对M31中的变星进行全面的分析，这可以用于几个新的天文学研究。本项目由美国国家科学基金会星系外天文学和宇宙学项目（AST/EXC）提供资金。****

CrottsAST-0070882The principal investigator and colleagues propose to study micolensing events in M31, using the background stars in that galaxy to identify microlenses in both M31 itself and in our own galaxy. The rate of lensing events is expected to be higher in M31 than in our galaxy or the LMC because the inclination of M31 allows us to see through a greater column density of stars. In addition to lensing objects, the surveys will also find intrinsically variable stars (such as Mira variables). A key question today in astrophysics is what composes the dark matter known to exist in galaxies. A crucial clue comes from observations which indicate that a large fraction of the mass of our Galaxy may be due to "Massive, Compact Halo Objects" (MACHOs), an interpretation which is highly controversial and difficult to understand. This proposal is to fund a three-year observational program, involving our nearest neighboring, large galaxy, M31 in Andromeda, which will settle the question of whether a large part of galaxy dark matter is composed of stellar massed objects in the halo. These results can be obtained well in advance of competing, proposed approaches, and settle the current quandary within the context of a galaxy separate from our own, indicating whether the MACHO halo is a universal phenomenon. The proposed study can address unsettled questions from Galactic surveys about the structure and content of the central Bulge, as well as produce a comprehensive assay of variable stars in M31, whichcan be used for several, new astronomical studies. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).****