Star Formation and the ISM Evolution of Galaxies Across Cosmic Time

宇宙时间中恒星的形成和星系的 ISM 演化

• 批准号: ST/I005544/1
• 负责人: Thomas Greve
• 金额: $ 60.13万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FI005544%2F1
• 关键词: Star; Formation; ISM; Evolution; Galaxies

Galaxies consist of stellar populations, a central supermassive black hole and a so-called interstellar medium (ISM). The latter is made up of gas and dust, with the gas consisting almost entirely of atomic and molecular hydrogen except for He (~10%) and a few other much less abundant atomic and molecular species. Stars form in overdense regions of the ISM that have become gravitationally unstable, while the supermassive black hole grows via the accretion of gas in the central regions of a galaxy. In other words, the ISM provides the 'fuel' for star formation and black hole growth, while the dust - condensing out of supernovae and stellar winds - is a consequence of star formation. Clearly the ISM plays a fundamental role in the formation and evolution of galaxies. Unfortunately, the bulk of the molecular gas is not directly observable due to the symmetry of the hydrogen molecule, which means that we have to rely on observations of emission lines from other molecules and atoms. The CO molecule, being the second-most abundant molecule after hydrogen and having easily excitable rotational quantum levels, is the principal tracer of the molecular ISM. By studying the brightness of the CO lines along with those of other useful, albeit observationally more challenging, tracers such as HCO+ and HCN, one is able to constrain the density, kinetic temperature and chemical composition of the gas. While these types of observations have been carried out in our own Galaxy, there are huge gaps in our understanding of the ISM in other galaxies. The reason for this is that, for low redshift galaxies, the key diagnostic emission lines of the ISM lie at far-infrared and submillimetre wavelengths, which are difficult or impossible to observe from the ground due to the Earth's atmosphere. The main objective of this research proposal is to obtain a detailed picture of the ISM in other galaxies, from local starburst galaxies in our Cosmic backyard to the most distant galaxies at the edge of the observable Universe. Using the full rotational line spectra of CO, HCN and HCO+ as well as diagnostic lines of neutral and single-ionised carbon we will characterize the physical and chemical properties of the ISM in galaxies. By delineating how the microscopic properties of the gas (i.e. density, temperature, chemical abundances) affect macroscopic processes such as star formation we will gain vital new insight into the star formation and ISM evolution of galaxies throughout the history of the Universe. To this end we will make use of new, extremely powerful telescopes in space and on the ground such as the Herschel Space Observatory and the Atacama Large Millimeter Array, which are able to overcome many of the difficulties that have faced ground-based observations to date. These facilities represent a quantum leap in our ability to study the gas and dust in distant galaxies, and will open up a new window in the study of star formation and ISM evolution in galaxies.

星系团由恒星群、中心超大质量黑洞和所谓的星际介质（ISM）组成。后者由气体和尘埃组成，气体几乎完全由原子和分子氢组成，除了He（~10%）和其他一些不太丰富的原子和分子物种。恒星形成于ISM的过密区域，这些区域已经变得引力不稳定，而超大质量黑洞则通过星系中心区域的气体吸积而成长。换句话说，ISM为星星的形成和黑洞的生长提供了“燃料”，而超新星和恒星风凝聚出的尘埃则是星星形成的结果。很明显，ISM在星系的形成和演化中起着重要作用。不幸的是，由于氢分子的对称性，大部分分子气体不能直接观察到，这意味着我们必须依赖于对其他分子和原子发射谱线的观察。CO分子是仅次于氢的第二丰富的分子，并且具有容易激发的旋转量子能级，是分子ISM的主要示踪剂。通过研究CO谱线的亮度沿着其他有用的（尽管在观测上更具挑战性）示踪剂（如HCO+和HCN）的亮度，人们能够限制气体的密度，动力学温度和化学成分。虽然这些类型的观测已经在我们自己的星系中进行，但我们对其他星系中ISM的理解存在巨大差距。其原因是，对于低红移星系，ISM的关键诊断发射线位于远红外和亚毫米波长，由于地球的大气层，很难或不可能从地面观察到。这项研究计划的主要目标是获得其他星系中ISM的详细图像，从我们宇宙后院的本地星暴星系到可观测宇宙边缘的最遥远星系。使用完整的旋转线光谱的CO，HCN和HCO+以及中性和单电离碳的诊断线，我们将表征的物理和化学性质的ISM星系。通过描绘气体的微观性质（即密度，温度，化学丰度）如何影响宏观过程，如星星形成，我们将获得至关重要的新的见解星星形成和ISM星系的演化在整个宇宙的历史。为此，我们将在空间和地面上使用新的、功能极其强大的望远镜，如赫歇尔空间天文台和阿塔卡马大型毫米波阵列，这些望远镜能够克服迄今为止地面观测所面临的许多困难。这些设施代表了我们研究遥远星系中气体和尘埃的能力的一个飞跃，并将为研究星系中星星形成和ISM演化打开一个新的窗口。

项目成果

Unveiling the molecular gas in the brightest and most distant star-forming galaxies discovered by the SPT

揭示 SPT 发现的最亮、最遥远的恒星形成星系中的分子气体

• 发表时间: 2013
• 期刊: ATNF Proposal
• 作者: Aravena Manuel

Resolved CO imaging in bright gravitationally lensed galaxies at z=2-6

z=2-6 明亮引力透镜星系中的解析 CO 成像

• 发表时间: 2014
• 期刊: ATNF Proposal
• 作者: Aravena Manuel

A survey of the cold molecular gas in gravitationally lensed star-forming galaxies at z > 2

对 z > 2 引力透镜恒星形成星系中冷分子气体的调查

• DOI: 10.1093/mnras/stw275
• 发表时间: 2016
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Aravena M

Unveiling the cold molecular gas in the brightest and most distant galaxies discovered with the SPT

揭示 SPT 发现的最亮和最遥远星系中的冷分子气体

• 发表时间: 2012
• 期刊: ATNF Proposal
• 作者: Aravena Manuel

Completing the CO spectral line energy distribution for luminous starburst galaxies discovered with the SPT

完成 SPT 发现的发光星暴星系的 CO 谱线能量分布

• 发表时间: 2013
• 期刊: ATNF Proposal
• 作者: Aravena Manuel