The cycle of life, death and rebirth in massive early-type galaxies; star formation, black-holes and feedback

巨大的早期型星系的生命、死亡和重生的循环；

• 批准号: ST/L004496/1
• 负责人: Timothy Davis
• 金额: $ 50.26万
• 依托单位: University of Hertfordshire
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FL004496%2F1
• 关键词: cycle; life; death; rebirth; massive

My research focuses on understanding the biggest galaxies that exist around us in the local universe. These objects are interesting because they are thought to be the end point of galaxy evolution. They are made up of billions of old stars, have red optical colours, and are generally thought to be free of cold gas - the fuel for new stars. Thus they are often described as "red and dead". Astronomers still don't fully know what caused these galaxies to die off, or if they can come back to life again. It is these processes that I am investigating.One of the ways astronomers think these massive galaxies become "red and dead" is due to the supermassive black-holes that lie at their cores. These enigmatic objects are clearly linked to galaxy formation, as they seem to grow in step with their galaxy host. In order to understand the role of black holes in the formation of galaxies, I developed a new technique to measure their masses, by tracing the motions of molecular gas clouds swirling around them. This technique is exciting, because it opens up the possibility of measuring black hole masses more accurately, and in more galaxies than ever before. As part of my Rutherford fellowship I aim to use this technique to reveal the dark monsters lurking at the hearts of nearby galaxies. When black holes swallow matter they emit large amounts of high energy light, and can accelerate large jets of particles. Both of these processes can affect gas clouds, throwing them out of galaxies. These outflows are one mechanism that can help form the gas-poor massive galaxies I study. A few years ago I helped identify one of the nearest examples of a black hole expelling large amounts of gas in this way. During my Rutherford fellowship I will use the chemistry of the gas in this outflow to determine whether it is the extremely strong light from the black hole, or the jet of particles that is causing the outflow we see. This will give us one more piece of the puzzle, helping to explain why most massive galaxies with big black holes are gas poor. Massive galaxies, like the ones I study, don't have to stay "red and dead". The can come back to life if material from dying stars can cool and become fuel for a new generation of stars. They can also merge with other small galaxies and steal their fuel. Around 1/4 of the massive "red and dead" galaxies around us today are currently in the process of being reborn. Understanding which process causes this, and what effect surrounding galaxies have, will allow us to determine whether these galaxies are destined to fail and go back to being "red and dead", or if they can eventually come back to life fully. I have discovered that these objects that have obtained fuel for star-formation, don't seem to be using it very effectively. They are very inefficient at forming stars when compared to galaxies like our own Milky Way. I aim to find out why this is happening, and what this can tell us about the physics controlling star formation in the universe.

我的研究重点是了解当地宇宙中我们周围存在的最大星系。这些物体很有趣，因为它们被认为是星系演化的终点。它们由数十亿颗老恒星组成，具有红色光学颜色，并且通常被认为不含冷气体——新恒星的燃料。因此，它们经常被描述为“红色和死亡”。天文学家仍然不完全知道是什么导致这些星系消亡，或者它们是否可以再次复活。我正在研究的正是这些过程。天文学家认为这些大质量星系变得“红色和死亡”的原因之一是由于位于其核心的超大质量黑洞。这些神秘的物体显然与星系的形成有关，因为它们似乎与星系宿主同步生长。为了了解黑洞在星系形成中的作用，我开发了一种新技术来测量黑洞的质量，通过追踪围绕黑洞旋转的分子气体云的运动。这项技术令人兴奋，因为它开启了更准确地测量黑洞质量的可能性，并且可以在比以往更多的星系中测量黑洞质量。作为卢瑟福奖学金的一部分，我的目标是利用这种技术来揭示潜伏在附近星系中心的黑暗怪物。当黑洞吞噬物质时，它们会发出大量高能光，并可以加速大量粒子流。这两个过程都会影响气体云，将它们从星系中抛出。这些流出是一种有助于形成我所研究的缺乏气体的大质量星系的机制。几年前，我帮助识别了最近的黑洞以这种方式排出大量气体的例子之一。在卢瑟福奖学金期间，我将利用这种流出物中气体的化学性质来确定是来自黑洞的极强光，还是导致我们看到的流出物的粒子射流。这将为我们提供更多的拼图，有助于解释为什么大多数具有大黑洞的大质量星系都缺乏气体。巨大的星系，就像我研究的星系一样，不必保持“红色和死亡”状态。如果垂死恒星的物质能够冷却并成为新一代恒星的燃料，它们就能复活。它们还可以与其他小星系合并并窃取它们的燃料。今天，我们周围大约 1/4 的巨大“红色和死亡”星系目前正处于重生过程中。了解导致这种情况的过程以及周围星系的影响，将使我们能够确定这些星系是否注定会失败并回到“红色和死亡”状态，或者它们最终是否能够完全复活。我发现这些获得恒星形成燃料的物体似乎并没有非常有效地利用它。与我们银河系等星系相比，它们形成恒星的效率非常低。我的目的是找出为什么会发生这种情况，以及这可以告诉我们关于控制宇宙中恒星形成的物理原理的什么信息。

项目成果

Spatially resolved variations of the IMF mass normalization in early-type galaxies as probed by molecular gas kinematics

通过分子气体运动学探测早期星系中 IMF 质量归一化的空间分辨变化

• DOI: 10.1093/mnras/stw2366
• 发表时间: 2016-09-12
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: T. Davis;R. McDermid
• 通讯作者: R. McDermid

A figure of merit for black hole mass measurements with molecular gas

用分子气体测量黑洞质量的品质因数

• DOI: 10.1093/mnras/stu1163
• 发表时间: 2014-06-10
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: T. Davis

The MASSIVE survey - III. Molecular gas and a broken Tully-Fisher relation in the most massive early-type galaxies

大规模调查 - III。

• DOI: http://dx.10.1093/mnras/stv2313
• 发表时间: 2015
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Davis T

NGC 1266 AS A LOCAL CANDIDATE FOR RAPID CESSATION OF STAR FORMATION

NGC 1266 是恒星形成迅速停止的本地候选者

• DOI: http://dx.10.1088/0004-637x/780/2/186
• 发表时间: 2013
• 期刊: The Astrophysical Journal
• 作者: Alatalo K

WISDOM Project - II. Molecular gas measurement of the supermassive black hole mass in NGC 4697

WISDOM 项目 - II。

• DOI: http://dx.10.1093/mnras/stw3217
• 发表时间: 2017
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Davis T