Merger histories of galaxies in the GECKOS survey

这个项目将研究星系合并历史和其盘结构之间的联系，并将利用壁虎，这是一项对附近35个边缘星系的VLT/MUSE新调查。为了恢复合并历史，存在一系列技术(例如，参见Marg等人2021年，Boecker等人2020年，朱等人2022年)。马蒂格等人(2021)提出的这项技术是基于这样的观点，即对于给定的年龄，被吸积的恒星比在原地形成的恒星更缺乏金属。这项技术需要测试和改进，它将是该项目的第一步：使用模拟来评估我们可以多好地根据年龄-金属丰度关系恢复过去的合并事件：通过这种方式可以识别哪些合并？我们能在多大程度上相信质量比和合并时间得出的结论？我们将为这个项目使用Artemis模拟，并将创建类似壁虎的模拟观测来测试该方法。第二步将使用我们所学到的知识，并描述所有壁虎星系的合并历史(我们还将制作吸积恒星目前所在位置的地图)。最后一步将收集在盘结构调查过程中获得的所有结果(薄盘和厚盘中的质量、年龄-速度关系、单龄种群的比例-高度、外盘中的耀斑、径向年龄梯度)。我们能否将合并事件与特定的特征联系起来，例如给定年龄的速度离散度的跃升，或者规模高度的增加？哪些并购案会产生巨大的厚盘？我们是否证实了Garcia de la Cruz等人(2021)关于合并对扩张和年龄梯度的影响的结果？有没有在没有合并的情况下似乎已经形成的厚厚的圆盘？

This project will examine the connection between a galaxy's merger history and the structure of its disc, and will take advantage of GECKOS, a new VLT/MUSE survey of 35 nearby edge-on galaxies.To recover merger histories, a range of techniques exist (see for instance Martig et al 2021, Boecker et al 2020, Zhu et al 2022). The technique presented in Martig et al (2021) is based on the idea that for a given age, accreted stars are more metal-poor than those formed in situ. This technique needs to be tested and refined, and it will be the first step of the project: to use simulations to assess how well we can recover past merger events based on the age-metallicity relation: which mergers can be identified that way? How much can we trust mass ratio and merger time derived? We will use the ARTEMIS simulations for this project, and will create mock GECKOS-like observations to test the method.The second step will be to use what we have learnt, and characterize the merger histories of all GECKOS galaxies (we will also produce maps of where accreted stars currently lie).The final step will be to gather all the results obtained within the course of the survey on the structure of discs (mass in thin and thick discs, age-velocity relation, scale-heights of mono-age populations, flaring in the outer disc, radial age gradients). Can we link merger events with particular signatures such as jumps in velocity dispersion at a given age, or increased scale-height? Which mergers produce massive thick discs? Do we confirm results from Garcia de la Cruz et al (2021) on the influence of mergers on flaring and age gradients? Are there thick discs that seem to have formed in the absence of mergers?