Merger histories of galaxies in the GECKOS survey

该项目将研究星系合并历史与其星系盘结构之间的联系，并将利用GECKOS，这是一项新的VLT/MUSE对35个附近边缘星系的调查。为了恢复合并历史，存在一系列技术（例如参见Martig等人2021，Boecker等人2020，Zhu等人2022）。Martig等人（2021）提出的技术是基于这样一种观点，即对于给定的年龄，吸积恒星比原地形成的恒星更缺乏金属。这项技术需要测试和改进，这将是项目的第一步：使用模拟来评估我们能在多大程度上根据年龄-金属丰度关系恢复过去的合并事件：哪些合并可以通过这种方式识别？我们能在多大程度上相信质量比和合并时间的推导？我们将在这个项目中使用ARTEMIS模拟，并创建类似geckos的模拟观测来测试该方法。第二步是利用我们所学到的知识，描绘所有GECKOS星系的合并历史（我们还将绘制吸积恒星当前所在位置的地图）。最后一步将是收集在调查过程中获得的关于圆盘结构的所有结果（薄盘和厚盘的质量，年龄-速度关系，单一年龄群体的比例-高度，外盘的燃烧，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，比如在给定年龄时速度弥散的跳跃，或者尺度高度的增加？哪些合并会产生巨大的厚盘？我们是否确认Garcia de la Cruz等人（2021）关于合并对燃烧和年龄梯度影响的结果？在没有合并的情况下是否存在厚盘？

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?