The formation of bars in massive disc galaxies

盘星系的形成和演化被认为主要包括两个主要阶段。在最初的湍流阶段之后，当与其他星系的猛烈合并起主要作用时，恒星和气体的圆盘以更均匀的配置安顿下来。在盘沉降之后，内部动力学过程常常导致在盘中形成条，即，相当数量的恒星开始以更加偏心的轨道运行，形成了细长的条。大量的理论研究表明，在恒星盘中，棒可以很容易地形成，无论是自发的还是在与其他星系的相互作用过程中。然而，在本地宇宙中，大约30%的盘星系没有酒吧，这一比例在宇宙年轻时更大。我们仍然不完全理解为什么一些盘星系仍然没有被限制，这个博士项目的主要目标是回答这个问题。重要的线索可能存在于恒星如何在无棒星系的圆盘中移动。因此，这就需要研究恒星的运动学和支配它们运动的引力的最终起源，然而，这个项目的科学成果并不局限于我们的主要问题。由于暗物质晕也会干扰条形的形成，这项研究的结果将揭示宇宙中暗物质的性质。此外，我们还将以前所未有的物理空间分辨率研究杆两端的恒星种群的特性，使我们能够以前所未有的方式研究螺旋臂和星系环等恒星结构的形成。这项工作将采用智利甚大望远镜MUSE积分场摄谱仪的最先进的档案数据。它将基于一套分析，以探索本地宇宙中数十个有棒和无棒星系样本中恒星的运动学、年龄和化学成分（例如，Gadotti等人，2020年; Bittner等人，2020年）。此外，我们将使用档案JWST数据来评估的分数和性质的棒星系在红移超过z ~ 1，并比较这些结果与早期的研究，采用HST数据。通过利用JWST改进的能力（与HST相比），这项研究将巩固我们对棒星系分数红移和性质演化的理解（例如，在国际研究团队中工作，学生将获得大型数据集，并行计算，光度分析和光谱拟合技术的经验。此外，他们将有机会参与（或领导）编写望远镜时间提案。如果提议成功，他们可以积极参与智利望远镜或其他观测站的观测。

The formation and evolution of disc galaxies is thought to consist essentially of two main phases. After the initial turbulent phase, when violent mergers with other galaxies play a major role, the disc of stars and gas settles in a more uniform configuration. After the disc settling, internal dynamical processes often lead to the formation of a bar in the disc, i.e., a significant number of stars begin to move in more eccentric orbits, forming the elongated bar. A number of theoretical studies shows that bars can form very easily in a stellar disc, either spontaneously or during interactions with other galaxies. Yet, about 30% of disc galaxies in the local Universe do not host a bar and this fraction was larger when the Universe was younger. We still do not fully understand why some disc galaxies remain unbarred and the main goal of this PhD project is to answer this question. Important clues may reside in how stars move in the discs of unbarred galaxies. This therefore calls for a study of the kinematics of stars and the ultimate origin of the gravitational forces that govern their movement.However, the scientific outcome of this project is not limited to our main question. Since dark matter haloes can also interfere with the formation of bars, the results of this investigation will shed light on the properties of dark matter in the Universe. In addition, we will investigate the properties of stellar populations at the ends of the bar with unprecedented physical spatial resolution, allowing us to study the formation of stellar structures such as spiral arms and galactic rings as never done before. This work will employ archival, state-of-the-art data from the integral-field spectrograph MUSE at the Very Large Telescope in Chile. It will be based on a suite of analyses to explore the kinematics, ages and chemical content of stars in a sample of tens of barred and unbarred galaxies in the local Universe (e.g., Gadotti et al. 2020; Bittner et al. 2020). Furthermore, we will use archival JWST data to assess the fraction and properties of barred galaxies at redshifts beyond z ~ 1, and compare these results with earlier studies that employed HST data. By making use of the JWST improved capabilities (as compared to HST) this study will consolidate our understanding on the evolution with redshift of the fraction and properties of barred galaxies (e.g., bar length and axial ratio).Working within an international team of researchers, the student will gain experience with large data sets, parallel computing, photometric analyses and spectral fitting techniques. Furthermore, they will have the opportunity to participate in (or lead) the writing of proposals for telescope time. If a proposal is successful, they may participate actively in the observations at the telescope in Chile or other observatory sites.