The Baryon Cycle in Massive Galaxies from the Bondi Sphere to the Halo

从邦迪球到光环的大质量星系中的重子循环

• 批准号: RGPIN-2017-04051
• 负责人: Mcnamara, Brian
• 金额: $ 4.08万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=690676
• 关键词: Baryon; Cycle; Massive; Galaxies; Bondi

Black holes are the most efficient power plants in the Universe. Fifty times more efficient than nuclear power, only one gram of matter falling toward a black hole every second could power the earth. Black holes are objects of infinite density surrounded by ghostly event horizons. An object wandering across the event horizon is swallowed and becomes lost to the universe forever. Not even light can escape. But how can power escape a black hole when nothing can escape it? ******Supermassive black holes weighing between one million and ten billion times the Sun lurk at the centres of all massive galaxies, including the Milky Way. Their enormous event horizons would enclose the entire solar system. As gas rushes toward a black hole it forms an accretion disk, much like water swirling down a drain. As the accretion disk spins around the event horizon, it becomes so hot that much of it is blown away as a wind of hot gas and radiation that permeates its entire host galaxy. Such an object, known as a quasar, is an early stage in the development of all massive galaxies. As nuclear black holes mature in size over billions of years of cosmic time, the energy of motion in an accretion disk is instead released in narrow, bipolar columns of particles, magnetic field, and radiation known as a radio jet. These jets and winds, travelling nearly at light speed, extend vast distances from the nucleus of the galaxy. The radio jets collide with the surrounding gas, preventing new stars from forming in the host galaxy. This mechanism, black hole feedback, is thought to govern the growth of galaxies.******Research led by my group over the past 15 years has shown how black hole feedback works at the centres of galaxy clusters. We discovered that radio jets inflate giant bubbles that rise like weather balloons through the tenuous atmospheres of galaxies and clusters. The bubbles heat the gas surrounding them on vast scales and apparently suppress the rate of star formation in their host galaxies. But how massive black holes are fueled is a mystery. Over the next five years my team will image cold molecular clouds that are likely fueling the jets and the stars forming around them. We will collect data from two of the most powerful telescopes in the world: the Atacama Large Millimeter Array (ALMA) and the earth-orbiting Chandra X-ray Observatory. We will use this data to study gas flows and winds in the gravitational grip of supermassive black holes. We will study the structure of the vast atmospheres surrounding galaxies where most of the energy released by black holes is captured and stored. Our ALMA Early Science program led to the discovery of massive, cold, molecular gas flows in galaxies that may have formed in the updrafts of giant X-ray bubbles. This program will reveal how molecular gas flows form and are powered, leading to a deeper understanding of their fundamental role in the formation and evolution of galaxies.

黑洞是宇宙中效率最高的发电厂。核能的效率是核能的50倍，每秒只有一克物质落入黑洞，就能为地球提供能量。黑洞是被幽灵事件视界包围的密度无限的物体。一个游荡在视界上的物体被吞没，并永远消失在宇宙中。即使是光也无法逃脱。但是，如果没有任何东西可以逃脱黑洞，能量怎么能逃脱呢？所有大质量星系的中心都潜伏着重量在太阳1000.01万亿倍之间的超大质量黑洞，包括银河系。它们巨大的事件视界将包围整个太阳系。当气体冲向黑洞时，它形成了一个吸积盘，就像水沿着排水沟旋转一样。当吸积盘围绕视界旋转时，它变得如此之热，以至于它的大部分被吹走，成为渗透到整个宿主星系的热气体和辐射的风。这种被称为类星体的天体是所有大质量星系发展的早期阶段。当核黑洞的大小在数十亿年的宇宙时间内成熟时，吸积盘中的运动能量反而以窄的、由粒子、磁场和辐射组成的两极柱释放，称为射电喷流。这些喷流和风以接近光速的速度行进，从银河系核心延伸到很远的地方。射电喷流与周围的气体相撞，阻止了在宿主星系中形成新的恒星。这种机制，即黑洞反馈，被认为控制着星系的增长。我的团队在过去15年领导的研究表明，黑洞反馈是如何在星系团的中心起作用的。我们发现，无线电喷气使巨大的气泡膨胀，这些气泡像天气气球一样在星系和星系团的稀薄大气中升起。这些气泡在很大程度上加热了它们周围的气体，显然抑制了它们所在星系中恒星的形成速度。但大质量黑洞是如何提供燃料的，这是一个谜。在接下来的五年里，我的团队将拍摄冷分子云的图像，这些云可能会为喷气式飞机和它们周围形成的恒星提供燃料。我们将从世界上最强大的两个望远镜收集数据：阿塔卡马大毫米阵列(ALMA)和绕地球轨道运行的钱德拉X射线天文台。我们将使用这些数据来研究超大质量黑洞引力作用下的气体流动和风。我们将研究星系周围巨大大气的结构，黑洞释放的大部分能量都是在那里被捕获和存储的。我们的ALMA早期科学计划导致在星系中发现了大量、寒冷的分子气体流动，这些气体可能是在巨大的X射线气泡的上升气流中形成的。这个项目将揭示分子气体流动是如何形成和提供动力的，从而加深对它们在星系形成和演化中的基础作用的理解。