The evolution of galaxies in the early universe with the next generation of telescopes

使用下一代望远镜观察早期宇宙中星系的演化

• 批准号: 2597404
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2597404
• 关键词: evolution; galaxies; early; universe; next

At the cutting-edge of Astronomy research is the study of the formation and evolution of the first galaxies. Through breakthrough observations in the past 30 years it has been possible to identify galaxies from when the universe was less than 500 million years old. These galaxies have unusual properties compared to the local universe, showing low chemical enrichment and dust obscuration, and irregular morphologies. The majority of studies of early galaxies to date have focused on 'typical' galaxies at that epoch, using deep pencil beam Hubble Space Telescope observations. These low mass, common high-redshift sources have been well studied however there is a lack of knowledge about the high mass end of the population. This project focuses on exploiting the current best datasets for understanding these bright, high mass galaxies. It is these rare and bright sources that are expected to be the sites of the earliest chemical enrichment and dust production in the early Universe. Furthermore, they are predicted to pinpoint the highest density environments. At z = 7, within the Epoch of Reionization, it is thought that the highest density regions will also be the most ionized, as both the central and associated/satellite galaxies produce ionizing photons that generate bubbles in the otherwise neutral Inter-galactic medium. Finally, simply the number density of the most massive sources provides key constraints on galaxy evolution, as it is these sources that are the hardest to produce in simulations. The role of AGN feedback, mergers and the star-formation efficiency in low-metallicity environments could all have a large impact on whether high SFR or mass galaxies can exist in the first billion years. Aims and objectivesThis project aims to exploit the current best wide-area datasets to find and study galaxies at high-redshift. At the end of the project the student will use the first data from the Vera Rubin Observatory (VRO) and Euclid space-mission to extend this research, putting them in an excellent position for future research if they choose this. The goal of the project is to understand when and how the most star-forming galaxies formed in the Universe. The student will become an expert in the selection of high-redshift galaxies from multi-band photometry. They will then use the resulting samples to constrain the evolution of the number density of these sources (via the luminosity function). To understand the astrophysics, these derived luminosity functions will be compared with a range of cosmological galaxy evolution models.The PhD can be split into 3-4 projects, all of which should lead to publications. In the first project the student will analyse the best available ground-based wide area surveys to search for z = 7 galaxies. This has not been done before using the VIDEO survey. Specificially they will pixel match the Subaru Hyper-Suprime Cam optical imaging to the VIDEO data in the XMM-LSS and CDFS fields. They will produce catalogues from these images, and do a robust Spectral-Energy Distribution fitting analysis to search for z = 7 candidates. The candidates will then be carefully inspected to remove any artefacts or contaminants (e.g. brown dwarfs). Once a final sample has been defined the student will compute the rest-frame UV luminosity function at these redshifts, extending this to very bright absolute magnitudes. The research method will build upon previous experience in the field. The luminosity functions will be analysed with a novel method that does not use binning (kernel density estimator). This will result in a strong first author publication. For the next 2-3 projects there are several options depending on the state of the field at this point, guided by the student's preference. I outline briefly the different projects below.1) Clustering analysis of high-redshift samples, to determine the likely halo masses and to study the star-formation efficiency as a function

天文学研究的前沿是研究第一个星系的形成和演化。通过过去30年的突破性观测，已经有可能确定宇宙年龄不到5亿年的星系。这些星系与当地宇宙相比具有不寻常的性质，显示出低化学富集和尘埃遮蔽，以及不规则的形态。迄今为止，大多数早期星系的研究都集中在那个时代的“典型”星系上，使用哈勃太空望远镜的深笔形光束观测。这些低质量的、常见的高红移源已经被很好地研究过，但是对人口中的高质量端缺乏了解。该项目的重点是利用目前最好的数据集来了解这些明亮的大质量星系。正是这些罕见而明亮的来源，被认为是早期宇宙中最早的化学富集和尘埃产生的地点。此外，预计它们将精确定位密度最高的环境。在z = 7时，在再电离时期内，密度最高的区域也被认为是最电离的，因为中心星系和关联星系/卫星星系都产生电离光子，在中性的星系间介质中产生气泡。最后，最大质量源的数量密度为星系演化提供了关键约束，因为这些源是最难在模拟中产生的。活动星系核的反馈、合并和低金属量环境中的恒星形成效率都可能对高SFR或大质量星系是否能在最初的10亿年中存在产生很大的影响。本项目旨在利用目前最好的广域数据集来发现和研究高红移星系。在项目结束时，学生将使用来自维拉鲁宾天文台（VRO）和欧几里得太空任务的第一批数据来扩展这项研究，如果他们选择这样做，他们将处于未来研究的绝佳位置。该项目的目标是了解宇宙中最具恒星形成的星系是何时以及如何形成的。学生将成为从多波段测光中选择高红移星系的专家。然后，他们将使用得到的样本来约束这些源的数量密度的演变（通过光度函数）。为了理解天体物理学，这些导出的光度函数将与一系列宇宙学星系演化模型进行比较。博士学位可以分为3-4个项目，所有这些项目都应该导致出版。在第一个项目中，学生将分析最好的地基广域调查，以寻找z = 7的星系。这在使用视频调查之前是没有做到的。具体来说，他们将像素匹配斯巴鲁超超凸轮光学成像的视频数据在XMM-LSS和CDFS领域。他们将从这些图像中生成目录，并进行强大的光谱能量分布拟合分析以搜索z = 7的候选者。然后将仔细检查候选者，以去除任何文物或污染物（例如褐矮星）。一旦定义了最终样本，学生将计算这些红移处的静止帧UV光度函数，并将其扩展到非常明亮的绝对星等。研究方法将建立在该领域以前的经验基础上。光度函数将用一种新的方法进行分析，该方法不使用分箱（核密度估计器）。这将导致一个强大的第一作者出版物。对于接下来的2-3个项目，有几个选项取决于现场的状态在这一点上，由学生的偏好指导。我在下面简要地概述了不同的项目：1）对高红移样品进行聚类分析，以确定可能的晕质量，并研究恒星形成效率的函数