Looking Out for the Little Guy: A Comprehensive Study of Star Formation in Dwarf Galaxies

2010年，大型综合巡天望远镜（LSST）被评为未来十年最重要的地面天文学项目。该望远镜将于2019年开始收集光线，并在两年后开始对可见天空进行全面调查。这项调查将发现数十亿个新的天体，包括我们银河系附近的数百个新星系。我们将发现的新星系是如此微弱，以至于以前的望远镜无法发现它们。这些微小的星系也是测试宇宙中星系起源等基本问题的理想场所。这项研究的重点是这些微小的星系对我们宇宙中形成的第一批恒星非常敏感。这一事实在以往的研究中没有得到充分的探讨。为了让天文学家了解这些星系告诉我们的关于宇宙起源的信息，这项研究集中在三个关键领域。首先，他们将预测国家科学基金会LSST应该发现的微弱星系的数量。其次，他们将预测LSST可能发现的暗星系离银河系有多远。第三，他们将预测这些星系中是否有任何一个今天仍在形成恒星，或者它们是否在数十亿年前就已经停止形成恒星。该研究提升了美国的科学领导地位，有助于维护美国在LSST上的投资。该项目的重点是培养第一代大学生，目标是使美国的技术劳动力多样化。扩大和多样化的科研队伍有助于确保美国在创新和经济增长方面保持领先地位。LSST将彻底改变我们对矮星系的认识，特别是在超微弱的区域。然而，模拟器几乎没有开始将他们成功的模型扩展到100万太阳质量以下的恒星。现在是了解我们目前的模拟是否可以继续解释星系形成到超微弱范围的关键时刻，或者是否需要对低质量暗物质晕中的恒星形成有新的理解。这项工作的目标是获得关于控制矮星系早期恒星形成和随后熄灭的过程的实质性知识。观测到的恒星质量低于1万个太阳质量的星系的数量在很大程度上取决于早期宇宙中第一批恒星形成的气体密度。这项工作将产生数百个模拟矮星系，其恒星质量从10亿个太阳质量（大约是银河系质量的1/10）到1000个太阳质量（在超微弱矮星系的范围内）不等。这项工作利用模拟来(1)精确定位恒星形成密度阈值对形成星系数量的作用，以及由此产生的恒星质量函数；(2)预测超暗矮星系数量与银河系半径的函数关系；(3)研究矮星系的猝灭过程作为质量和环境的函数，并在现场预测可被未来设施观测到的猝灭比例。这项工作还建立了一个项目，以支持和指导第一代大学生（其中许多人可能也来自历史上在STEM中代表性不足的群体）过渡到本科生。该项目将(1)在学生和罗格斯大学物理与天文系成员之间建立师友关系，(2)利用队列建设活动将学生发展成彼此之间的同伴支持网络，(3)向学生介绍基本研究工具并让他们参与原创研究。这三个目标已经被证明可以增加在科学领域代表性不足的学生的保留率。总体目标是提高罗格斯大学物理学和天文学本科专业以及物理学和天文学社区的人口多样性。该项目还将培训研究生教授和指导一年级学生，并就一年级学生/代表性不足的学生面临的公平和教育障碍问题对研究生导师进行教育。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。

In 2010, the Large Synoptic Survey Telescope (LSST) was named the top-ranked ground-based astronomy project for the coming decade. The telescope will begin gathering light in 2019, and begin a full survey of the visible sky two years later. The survey will discover billions of new astronomical objects, including hundreds of new galaxies nearby to our own Milky Way galaxy. The new galaxies that we will discover are so faint that they could not be found by previous telescopes. These tiny galaxies are also ideal places to test fundamental questions about the origin of galaxies in our Universe. This research focuses on the fact that these tiny galaxies are very sensitive to the first stars that formed in our Universe. This fact has not been sufficiently explored in previous research. To prepare astronomers to understand what these galaxies tell us about the origins of our Universe, this research focuses on three key areas. First, they will predict the number of faint galaxies that the National Science Foundation's LSST should discover. Second, they will predict how far away from the Milky Way the LSST might find the faint galaxies. Third, they will predict whether any of these galaxies is still forming stars today, or whether they all stopped forming stars billions of years ago. The research advances the scientific leadership of the United States and help to safeguard the United States' investment in LSST. The project focuses on training students who are first-generation college students, with the goal of diversifying the US technical workforce. An expanded and diversified scientific workforce helps to ensure that the US remains a leader in innovation and economic growth.The LSST will revolutionize our knowledge of dwarf galaxies, especially in the ultra-faint regime. However, simulators have barely begun to extend their successful models to stellar masses below 1 million solar masses. Now is the critical time to understand whether our current simulations can continue to explain galaxy formation down into the ultra-faint range, or whether a new understanding of star formation in low mass dark matter halos will be required. The goal of this work is to gain substantial knowledge about the processes that control early star formation in dwarf galaxies and subsequent quenching. The number of observed galaxies with stellar masses below 10 thousand solar masses depends strongly on the density of gas from which the first stars could form in the early Universe. The proposed work will generate hundreds of simulated dwarf galaxies, with stellar masses ranging from one billion solar masses (roughly 1/10 the mass of the Milky Way) down to 1000 solar masses in the range of ultra-faint dwarf galaxies. This work utilizes the simulations to (1) pinpoint the role of star formation density threshold on the number of galaxies that form, and the resulting stellar mass function; (2) make predictions for the number of ultra-faint dwarf galaxies as function of radius from the Milky Way; (3) study the processes that quench dwarf galaxies as function of mass and environment, and make predictions for the quenched fraction in the field that can be observed by future facilities. This work also establishes a program to support and mentor first-generation college students (many of whom are likely to also be from groups historically underrepresented in STEM) as they transition to being undergraduates. The program will (1) develop a mentoring relationship between students and members of the Rutgers Physics & Astronomy department, (2) utilize cohort building activities to develop the students into a peer support network for each other, (3) introduce the students to basic research tools and get them involved in original research. These three goals have been shown to increase the retention of underrepresented students in science. The overall aim is to improve the demographic diversity of both the Rutgers Physics & Astronomy undergraduate majors, but also of the Physics and Astronomy community. This program will also train graduate students to teach and mentor the first-year students, and educate the graduate student mentors on issues of equity and barriers to education that first-year/underrepresented students face.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.