Star Formation and Protoplanetary Discs

恒星形成和原行星盘

• 批准号: ST/I001557/1
• 负责人: Melvin Hoare
• 金额: $ 197.02万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FI001557%2F1
• 关键词: Star; Formation; Protoplanetary; Discs

This research programme addresses key questions on how stars form from clouds of dust and gas in galaxies. We also investigate processes at work in the swirling discs that feed material onto the new stars: the very discs that evolve to form planets. Magnetic fields pervade interstellar space and play a crucial role in controlling how material can accumulate into ever denser cores as gravity takes hold during the collapse to a star-planet system. Even though stellar birth sites are cold and dense there are still some charged particles such as electrons, molecular ions and, importantly, charged grains of dust. We will investigate with computer simulations how the presence of charged dust grains affects the formation of stars and discs. Observationally we will study these processes using ESA's new Herschel satellite which will provide the first sensitive spectrum in the far-infrared region where many molecules emit. This will be coupled with detailed mapping of molecular emission from the ground with arrays of telescopes operating in the microwave region, and especially the new ALMA telescope in Chile with 66 dishes working in tandem. The chemical composition of these clouds and the insight from the blue- and red- shifts of their emission lines will allow us to infer what processes are controlling these crucial early stages in the birth of stars. The high level of spatial detail afforded by the new ALMA telescope will also be used to map out the infall onto stars much more massive than our Sun. Their formation has proved to be much more problematic as they are rare and distant and produce prodigious amounts of radiation that blow material away rather than let it fall in. We will study a sample of massive forming stars which is close to being complete across the whole Galaxy, that we have found from following up an infrared survey of our Galaxy with the American MSX satellite. As the material gets close in to the star we expect it to complete its journey in a thin disc orbiting the star. We will systematically search our sample for these discs using the new technique of infrared interferometry which combines the light from two or three of the large 8 m telescopes of the VLT. In addition, we can use very high quality spectra from single telescopes to look for tiny spatial shifts from lines that arise from the disc relative to the starlight to gain spatial information at levels 10 to 100 times better than the Hubble Space Telescope. At the same time that material is spiralling onto a star via a disc, some of it is being ejected at high speeds along the rotation axis. It is thought that magnetic fields are responsible for accelerating and channelling material into these jets. We will use the highly sensitive new network of radio dishes in the UK, e-Merlin, to map the emission from these jets and study how these plough into the surrounding infalling molecular material to blow holes in the cloud. The combination of radio, microwave and infrared observations across a wide range of masses and stages of evolution will enable us to disentangle the various competing processes at work. As massive stars finally begin to clear away the material from which they were born the combined effect of the winds driven by their strong radiation fields has a dramatic effect. The clumpy cloud gets shredded by the fast wind whistling through the less dense regions. As it slams into the molecular material it gets heated to millions of degrees and emits strongly in the X-ray region as observed with NASA's Chandra satellite. The winds colliding with each other can also accelerate particles and produce the so-called cosmic rays and we should see evidence of this at radio and gamma ray wavelengths. Computer simulations will be used to tackle this problem to investigate how these processes can terminate the star formation episodes in giant molecular clouds and in other galaxies where concentrated bursts of massive star formation take place.

该研究方案解决了关于恒星如何从星系中的尘埃和气体云形成的关键问题。我们还研究了旋转盘中的工作过程，这些旋转盘将物质输送到新恒星上：正是这些旋转盘演变成行星。磁场遍布星际空间，在控制物质如何积聚成更致密的核心方面发挥着至关重要的作用，因为在恒星-行星系统坍缩期间，引力占据了主导地位。尽管恒星诞生地寒冷而密集，但仍然存在一些带电粒子，如电子，分子离子，更重要的是，带电尘埃颗粒。我们将通过计算机模拟研究带电尘埃颗粒的存在如何影响恒星和圆盘的形成。在观测上，我们将使用欧空局的新赫歇尔卫星研究这些过程，该卫星将提供许多分子发射的远红外区域的第一个敏感光谱。与此同时，还将利用在微波区工作的望远镜阵列，特别是智利新的阿尔马望远镜，对地面的分子发射进行详细测绘，该望远镜有66个碟形天线协同工作。这些云的化学成分以及它们发射线的蓝移和红移的洞察力将使我们能够推断出是什么过程控制着恒星诞生的这些关键早期阶段。新的阿尔马望远镜所提供的高水平的空间细节也将被用来绘制出比我们的太阳大得多的恒星的坠落。它们的形成被证明是更有问题的，因为它们是罕见的和遥远的，并产生大量的辐射，吹走物质，而不是让它落入。我们将研究整个银河系中接近完整的大质量形成恒星的样本，这是我们用美国MSX卫星对银河系进行红外线调查后发现的。当这些物质接近星星时，我们预计它将在一个围绕星星旋转的薄圆盘中完成它的旅程。我们将系统地搜索我们的样本，这些光盘使用新的红外干涉测量技术，结合从两个或三个大型8米望远镜的VLT的光。此外，我们可以使用来自单个望远镜的非常高质量的光谱来寻找相对于星光的圆盘产生的线的微小空间偏移，以获得比哈勃太空望远镜好10到100倍的空间信息。在物质通过圆盘螺旋式地落在星星上的同时，其中一些物质正沿着旋转轴沿着高速喷射。人们认为磁场是加速和引导物质进入这些射流的原因。我们将使用英国高灵敏度的新型无线电碟形天线网络e-Merlin来绘制这些射流的发射图，并研究这些射流如何犁入周围的下落分子物质，在云中打出洞。无线电，微波和红外线观测的组合跨越了广泛的质量和演化阶段，将使我们能够解开工作中的各种竞争过程。当大质量恒星最终开始清除它们诞生的物质时，由它们强大的辐射场驱动的风的综合效应产生了戏剧性的效果。云团被呼啸而过的强风撕碎。当它猛烈撞击分子物质时，它被加热到数百万度，并在X射线区域发出强烈的辐射，这是美国宇航局钱德拉卫星观察到的。风相互碰撞也可以加速粒子并产生所谓的宇宙射线，我们应该在无线电和伽马射线波长处看到这方面的证据。计算机模拟将被用来解决这个问题，以调查这些过程如何可以终止在巨大的分子云和其他星系的大质量星星形成集中爆发发生的星星形成插曲。

项目成果

INITIAL CONDITIONS FOR STAR FORMATION IN CLUSTERS: PHYSICAL AND KINEMATICAL STRUCTURE OF THE STARLESS CORE Oph A-N6

• DOI: 10.1088/0004-637x/745/2/117
• 发表时间: 2011-11
• 期刊: The Astrophysical Journal
• 作者: T. Bourke;P. Myers;P. Caselli;J. di Francesco;A. Belloche;R. Plume;D. Wilner

Numerical simulations of a shock interacting with multiple magnetized clouds

冲击与多个磁化云相互作用的数值模拟

• DOI: 10.1093/mnras/stu1501
• 发表时间: 2014
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Aluzas R

A statistical spectropolarimetric study of Herbig Ae/Be stars

Herbig Ae/Be 星的统计光谱偏振研究

• DOI: 10.1093/mnras/stx1891
• 发表时间: 2017
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Ababakr K

First observations of CN (2-1), HCO+ (3-2) and C2H (3-2) emission lines in the Perseus cluster: constraints on heating mechanisms in the cluster gas Molecules as heating probe in Perseus

英仙座星团中 CN (2-1)、HCO (3-2) 和 C2H (3-2) 发射线的首次观测：星团气体中加热机制的限制 英仙座中作为加热探针的分子

• DOI: 10.1111/j.1365-2966.2011.19304.x
• 发表时间: 2011
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Bayet E

Numerical simulations of shocks encountering clumpy regions Simulations of shocks encountering clumpy regions

遇到块状区域的冲击的数值模拟 遇到块状区域的冲击的数值模拟

• DOI: 10.1111/j.1365-2966.2012.21598.x
• 发表时间: 2012
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Aluzas R