Feeding the Beasts: Shedding light on the formation processes of today's most massive galaxies.

喂养野兽：揭示当今最大质量星系的形成过程。

• 批准号: RGPIN-2020-04606
• 负责人: Webb, Tracy
• 金额: $ 2.99万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762604
• 关键词: Feeding; Beasts; Shedding; light; formation

We have discovered a new - an unexpected - formation mechanism for the most massive galaxies in the universe: Brightest Cluster Galaxies or BCGs.  These systems sit at the centre of rich and massive galaxy clusters, held together by the mutual gravity of their components. Although the standard accepted theory indicates that BCGs should assemble the bulk of their stellar mass through the accretion of smaller gas-poor systems (the so-called hierarchical structure formation scenario) the recent results of my team have shown that substantial in-situ star formation occurs in young BCGs. This is a key result since, as an extreme outcome of evolution, these massive systems are sensitive probes of the models of galaxy formation. It is also surprising as it flies in the face of our understanding of how galaxy clusters accrete galaxies:  during in-fall into the cluster the galaxies should be stripped of their interstellar medium and be gas poor by the time they merge wit the BCG - thus making star formation impossible. Yet the immense amount of star formation in and around BCGs indicate that large amounts of fuel have been deposited into the centres of these galaxy clusters.  Over the next five years, my team will undertake an ambitious observational program to elucidate the nature of the gas deposition and star formation in these systems.  Specifically, our objective is to understand what triggered the intense star formation we have measured, what sustains it and what will eventually quench it.   This will require an approach the spans the electromagnetic spectrum of light as different processes emit light at different wavelengths. We will employ the newly-online and next generation facilities such as the Atacama Large Millimetre Array and the James Webb Space telescope, as well as established workhorses such as the Gemini 8m optical telescopes and the Jansky Very Large (radio) Array.    The program will encompass the three main aspects of galaxy stellar mass assembly:  (i) the current or ongoing star formation; (ii) the existing stars, or the historical star formation and; (iii) the molecular gas fuel, or the future star formation.  This three-pronged approach will clarify for the first time, the formation mechanisms of these massive beasts and provide new constraints for the models and theory which form the basis of our understanding of massive galaxy evolution.

我们发现了宇宙中最大质量星系的一种新的——一种意想不到的——形成机制：最亮的星系团或BCG，这些系统位于丰富而巨大的星系团的中心，通过其组成部分的相互引力结合在一起。尽管公认的标准理论表明 BCG 应该通过较小的贫气系统的吸积来聚集其大部分恒星质量（所谓的分层结构形成场景），但我的团队最近的结果表明，大量的原位恒星这是一个关键的结果，因为作为进化的极端结果，这些巨大的系统是星系形成模型的敏感探针，它与我们对星系团如何形成的理解相悖，这也令人惊讶。增生星系：在落入星团的过程中，星系在与 BCG 合并时应该会被剥离其星际介质，并且气体匮乏，从而使恒星形成变得不可能，但 BCG 内部和周围的大量恒星形成表明。大量燃料已沉积到这些星系团的中心，在接下来的五年中，我的团队将开展一项雄心勃勃的观测计划，以阐明这些系统中气体沉积和恒星形成的性质。目标是了解是什么触发了我们测量到的强烈的恒星形成，什么维持了它，什么最终会熄灭它，这将需要一种跨越光的电磁频谱的方法，因为我们将在不同的过程中发射不同波长的光。采用新上线的下一代设施，如阿塔卡马大型毫米波阵列和詹姆斯·韦伯太空望远镜，以及现有的主力设备，如双子座 8m 光学望远镜和扬斯基甚大（射电）阵列。星系恒星质量聚集的三个主要方面：（i）当前或正在进行的恒星形成；（ii）现有恒星，或历史恒星形成；（iii）分子气体燃料，或这种三管齐下的方法将首次阐明这些巨大星系的形成机制，并为构成我们理解大质量星系演化基础的模型和理论提供新的约束。