When are Disk Galaxies First Assembled?

如今，几乎所有正在积极形成恒星的星系都是盘状星系。我们自己的星系，银河系，就是一个例子。盘状星系由薄而对称的恒星和气体旋转盘组成。该项目将确定盘状星系首次大量形成的时间。研究人员将测量过去 100 亿年来盘状星系的比例。这些分数将与磁盘形成的两个理论模型进行比较，以了解磁盘是如何形成的。此外，还将对星系的理论模型进行模拟观测。大量的模拟观测结果将用于训练分类算法，以自动区分圆盘和碰撞星系，因为它们很容易被误认为是圆盘。然后，所得算法将应用于数百个星系的现有观测，以识别圆盘的部分。该项目还将针对当地历史黑人学院和大学（HBCU）的学生开设“Astro Scholars”年度为期一周的强化迷你课程。学者将获得财政支持。夏季计划后每月进行的跟踪将使该计划的影响延长 6 个月。目前对盘状星系比例的测量不准确。他们没有考虑到一些碰撞星系可能看起来是盘状星系。为了测量磁盘随时间变化的比例，研究人员将创建磁盘标准。这些标准将确定给定的观测结果是否表明存在圆盘或碰撞星系。该标准将通过使用公开的计算机模拟套件 VELA 和 FIRE 的星系模型来创建。研究人员将使用模拟目录来模拟观测，并将其直接与观测结果进行比较，同时考虑到地球大气层的模糊影响。研究人员将通过将模拟的内在状态（磁盘或碰撞）与模拟的观察结果进行比较来创建磁盘标准。这些标准将表明观测结果是圆盘或碰撞星系的概率。这些标准将应用于近600个星系的KMOS3D整体场单元观测。他们将测量随着时间的推移，盘状恒星形成星系的比例。圆盘标准将成为最近（和正在进行的）大型星系运动学调查的强大工具。它们将成为下一代调查的关键，这些调查将把星系运动学的观测推向早期宇宙，当时第一个星系形成，星系碰撞甚至更加频繁。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Today nearly all galaxies that are actively forming stars are disk galaxies. Our own galaxy, the Milky Way, is one example. Disk galaxies are composed of a thin and symmetric rotating disk of stars and gas. This project will determine when disk galaxies first formed in significant numbers. Researchers will measure the fraction of disk galaxies over the last 10 billion years. These fractions will be compared with two theoretical models for disk formation in order to understand how disks form. In addition, simulated observations will be made of theoretical models of galaxies. A large set of these simulated observations will be used to train a classification algorithm to automatically distinguish between disks and colliding galaxies, which are easily mistaken for disks. The resulting algorithm will then be applied to existing observations of hundreds of galaxies in order to identify the fraction of disks. This project will also establish an "Astro Scholars" annual week-long intensive mini-course targeted at students in local Historically Black Colleges and Universities (HBCUs). Scholars will receive financial support. Monthly follow- up after the summer program will extend the impact of the program for 6 months.Current measurements of the fraction of disk galaxies are inaccurate. They do not take into account that some colliding galaxies can appear to be disk galaxies. To measure the fraction of disks over time, researchers will create disk criteria. These criteria will determine if a given observation indicates a disk or colliding galaxies. The criteria will be created with models of galaxies using publicly available suites, VELA and FIRE, of computer simulations. Researchers will simulate observations with mock catalogues that will be compared directly to observations, taking into account the blurring effects of the Earth's atmosphere. Researchers will create disk criteria by comparing the intrinsic states of the simulations (disk or collision) with the simulated observations. These criteria will indicate the probability an observation is a disk or colliding galaxies. These criteria will be applied to KMOS3D integral field unit observations of nearly 600 galaxies. They will measure the fraction of star-forming galaxies which are disks over time. The disk criteria will serve as a powerful tool for recent (and ongoing) large surveys of galaxy kinematics. They will be key for next-generation surveys that will push observations of galaxy kinematics to the very early universe, when the first galaxies formed, and galaxy collisions were even more frequent.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.