Ancient and Recent Galaxy Mergers

古代和近代的星系合并Francois Schweizer过去星系的碰撞和合并似乎在决定当今星系的形状和动力学方面发挥了重要作用。 虽然星系合并的数量随着时间的推移而减少，但仍有一些这样的合并正在发生，并为我们提供了过去进化过程的宝贵线索。 施韦泽博士正在确定附近星系古代和近代合并事件的日期。 年轻球状星星团的发现显然是在合并过程中形成的，这使得一种确定合并事件本身年代的新方法成为可能。 由于是同时代的恒星，球状星团比整个星系更容易定年。 Schweizer博士正在进行六个项目：（1）分析六个合并星系的图像，以寻找其中年轻到中等年龄的球状星团;（2）建立球状星团年表;（3）确定星团的大尺度空间分布;（4）测量这些星团的金属丰度和年龄;（5）确定它们的年龄。（5）绘制三个合并星系中恒星和气体的速度图，以确定合并动力学;（6）在合并残余物NGC 7252中寻找残余星系风和可能的大尺度激波锋面。 这些项目解决了星系起源的关键问题，其中球状星团的年龄和金属丰度，合并残余物中奇怪旋转核心的形成，以及合并过程中气体的命运。

Ancient and recent galaxy mergersFrancois SchweizerCollisions and mergers of galaxies in the past seem to have played a major role in determining the shapes and dynamics of present day galaxies. Though the number of galactic mergers has declined with time, a few such mergers are still occurring and offer us valuable clues to past evolutionary processes. Dr. Schweizer is determining the dates of ancient and recent merger events in nearby galaxies. Discoveries of young globular star clusters apparently formed during mergers have made possible a new method for dating the merger events themselves. Because of the coeval stars, globular clusters are more easily dated than whole galaxies. Dr. Schweizer is conducting six projects: (1) an analysis of images of six merger galaxies to search young to intermediate age globular clusters in them; (2) establish a globular cluster chronology; (3) determine the large scale spatial distribution of the clusters; (4) measure metallicities and ages of these clusters; (5) map the velocities of the stars and gas in three merger galaxies to determine the merger dynamics; and (6) search for a remnant galactic wind and possible large scale shock fronts in the merger remnant NGC 7252. These projects address key questions on the origins of galaxies, the ages and metallicities of globular clusters in them, the formation of oddly rotating cores in merger remnants, and the fate of gas during mergers.