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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=710796
• 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.

黑洞是宇宙中最有效的发电厂。 效率是核能的50倍，每秒只有一克物质落入黑洞，就可以为地球提供动力。 黑洞是被幽灵般的事件视界所包围的无限密度的物体。一个在事件视界上游荡的物体被吞噬，永远消失在宇宙中。 连光都逃不掉。 但是，当没有任何东西可以逃脱黑洞时，能量如何逃脱黑洞呢？ 质量在太阳100万到100亿倍之间的超大质量黑洞潜伏在所有大质量星系的中心，包括银河系。 它们巨大的视界将包围整个太阳系。 当气体冲向黑洞时，它会形成一个吸积盘，就像水在排水沟里旋转一样。 当吸积盘围绕视界旋转时，它变得如此之热，以至于大部分都被吹走，成为热气体和辐射的风，渗透到整个宿主星系。 这样的物体，被称为类星体，是所有大质量星系发展的早期阶段。 随着核黑洞在数十亿年的宇宙时间中逐渐成熟，吸积盘中的运动能量反而以狭窄的双极粒子柱，磁场和辐射释放出来，称为无线电喷流。 这些喷流和风以接近光速的速度从星系核延伸出很远的距离。 射电喷流与周围的气体碰撞，阻止了宿主星系中新恒星的形成。 这种机制，黑洞反馈，被认为是控制星系的生长。 在过去的15年里，我的团队领导的研究已经展示了黑洞反馈在星系团中心的作用。 我们发现射电喷流会使巨大的气泡膨胀，这些气泡像气象气球一样上升，穿过星系和星系团的稀薄大气。 这些气泡在巨大的尺度上加热周围的气体，显然抑制了宿主星系中星星的形成速度。 但大质量黑洞是如何形成的仍是个谜。在接下来的五年里，我的团队将拍摄冷分子云的图像，这些云可能为喷流和在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：阿塔卡马大型毫米波阵列（阿尔马）和绕地轨道的钱德拉X射线天文台。 我们将利用这些数据来研究超大质量黑洞引力控制下的气体流动和风。 我们将研究星系周围巨大大气层的结构，黑洞释放的大部分能量都被捕获和储存在那里。 我们的阿尔马早期科学计划导致在星系中发现了大量的、冷的分子气体流，这些气体流可能是在巨大的X射线气泡的上升气流中形成的。 该计划将揭示分子气体流的形成和动力，从而更深入地了解它们在星系形成和演化中的基本作用。