When are Disk Galaxies First Assembled?

今天，几乎所有活跃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。盘状星系是由一个由恒星和气体组成的薄而对称的旋转盘组成的。这个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100亿年间盘状星系的比例。这些分数将与磁盘形成的两个理论模型进行比较，以便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。大量这些模拟观测数据将用于训练一种分类算法，以自动区分圆盘和碰撞星系，后者很容易被误认为是圆盘。由此产生的算法随后将被应用于对数百个星系的现有观测，以确定圆盘的比例。该项目还将针对当地历史悠久的黑人学院和大学（HBCUs）的学生，每年开设为期一周的“天文学学者”强化迷你课程。学者将获得财政支持。夏季课程结束后的每月跟进将使课程的影响延长6个月。目前对盘状星系比例的测量是不准确的。他们没有考虑到一些碰撞的星系看起来可能是盘状星系。为了测量磁盘随时间的比例，研究人员将创建磁盘标准。这些标准将决定给定的观测是否表明存在圆盘或碰撞星系。这些标准将通过使用公开可用的计算机模拟套件VELA和FIRE的星系模型来创建。研究人员将用模拟目录来模拟观测结果，并将其直接与观测结果进行比较，同时考虑到地球大气的模糊效应。研究人员将通过比较模拟的内在状态（磁盘或碰撞）与模拟的观察结果来创建磁盘标准。这些标准将表明观测到的是圆盘或星系碰撞的可能性。这些标准将应用于KMOS3D对近600个星系的积分场单位观测。随着时间的推移，他们将测量形成恒星的星系中盘状星系的比例。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有力工具。它们将是下一代调查的关键，这些调查将把对星系运动学的观察推向非常早期的宇宙，那时第一个星系形成，星系碰撞更加频繁。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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.