When Did Quiescent Galaxies First Appear and What Quenched Their Star-Formation?

静止星系何时首次出现以及是什么终止了它们的恒星形成？

• 批准号: 1513473
• 负责人: Danilo Marchesini
• 金额: $ 39.54万
• 依托单位: Tufts University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1513473&HistoricalAwards=false
• 关键词: When; Did; Quiescent; Galaxies; First

Galaxies are vast collections of stars, gas, dust, and dark matter, and come in various sizes, shapes, and colors. Understanding how the different types of galaxies formed is one of the major quests in astrophysics. Today, the biggest and heaviest galaxies in the local universe are found to be quiescent (i.e., not forming new stars) and made of very old stars, with typical ages of 12 billion years. To understand how these nearby galaxies formed, their counterparts in the distant, young universe need to be studied as well. Dr. Marchesini and his team will investigate quiescent galaxies over 95% of cosmic history using the highest quality astronomical observations. The findings will be compared with theoretical predictions, providing new clues on what switches off star formation in the early phase of galaxy formation. Besides training graduate and undergraduate students, Dr. Marchesini will implement a summer research program for high-school students, contribute to the professional development of K-12 science teachers, and deliver public lectures. The project includes construction of multi-wavelength photometric catalogs of galaxies using data from the Hubble Frontier Fields, ground-based telescopes (Keck and VLT), and Spitzer-IRAC. The spectral energy distributions of the detected galaxies will be modeled to derive photometric redshifts and stellar population properties. The evolution of the stellar mass function of galaxies since redshift z=7 will be measured, with particular emphasis on the quiescent galaxy population.

星系是恒星、气体、尘埃和暗物质的巨大集合，有各种大小、形状和颜色。了解不同类型的星系是如何形成的是天体物理学的主要任务之一。如今，当地宇宙中最大、最重的星系被发现处于静止状态（即不形成新恒星），并且由非常古老的恒星组成，典型年龄为 120 亿年。为了了解这些附近的星系是如何形成的，还需要研究它们在遥远、年轻的宇宙中的对应星系。 Marchesini 博士和他的团队将利用最高质量的天文观测来研究超过 95% 的宇宙历史中的静止星系。这些发现将与理论预测进行比较，为了解星系形成早期阶段恒星形成的原因提供新线索。除了培训研究生和本科生外，Marchesini 博士还将为高中生实施暑期研究计划，为 K-12 科学教师的专业发展做出贡献，并进行公开讲座。该项目包括使用来自哈勃前沿场、地面望远镜（Keck 和 VLT）和 Spitzer-IRAC 的数据构建星系的多波长光度目录。将对探测到的星系的光谱能量分布进行建模，以得出光度红移和恒星种群特性。将测量自红移 z=7 以来星系恒星质量函数的演化，特别强调静止星系群。