Extragalactic Radio Sources and Galaxy Formation

河外射电源和星系形成

• 批准号: RGPIN-2014-05735
• 负责人: Wall, Jasper
• 金额: $ 1.66万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=567357
• 关键词: Extragalactic; Radio; Sources; Galaxy; Formation

We observe that we live, and we live in a universe of galaxies, massive ordered collections of billions of stars, many of which have planets, with life on one at least. The "why" we live is philosophy, religion; the "how it happened" is the realm of science. Our centuries of observation have led us to a current consensus cosmology of the "how"; but this consensus cosmology is stranger than fiction. The "how" goes like this. Small fluctuations in our early Universe, seen imprinted on the Cosmic Radio Background, were the seeds around which larger and messy structures were collected by gravity - the early galaxies. These were lit up by stars, also formed by gravity, the copious fuel of primordial hydrogen and helium gas created in the Big Bang collapsing in to form the first nuclear-power generators. The galaxies grew and became ordered as stellar orbits settled into gravity-driven patterns: generally spirals or ellipticals. Clustering in gravity hierarchy settled these galaxies into a design called the "Cosmic Web", a network of galaxies in clusters and in thin filaments whose intersections - nodes - represent clusters of clusters. At the end of the 20th century the picture changed to become dramatically strange. Nobel-prize winning observations of supernovae in distant galaxies forced the deduction that our Universe is being accelerated by a mystical "Dark Energy". Its origins are either simple, as a possible outcome of General Relativity, or complex, from geometry and physics not yet conceived. Dark Energy constitutes 70% of the mass of the Universe. Another 25% is in "Dark Matter", weakly-interacting particles that we cannot yet observe. The remaining 5% is in the form of matter that we know and love, and of which we, the Earth and our Universe of observable galaxies are all made - baryons, constituting standard atoms and molecules. This is the "LambdaCDM" cosmology, Lambda describing the unknown accelerant, CDM the Cold Dark Matter: 95% of our Universe remains to be understood. Galaxy formation in such a universe is a tricky balancing act. The LambdaCDM cosmology invites hierarchical gravity formation of galaxies in the cosmic web. But left unchecked it is too successful - and all the galaxies around us, the local galaxies, should be blue, forming stars, and huge. Instead they are generally old, "red and dead", and small. Something stops galaxy formation in its tracks. That charge is now laid at the door of radio AGN, radio Active Galactic Nuclei, galaxies with double-lobed radio sources powered by twin relativistic beams from a central super-massive black hole (SMBH). We know from measuring the spin of galaxies that most have a black hole at the centre, and that large galaxies harbour SMBHs. The energy these blast out via their twin-jet systems can carve giant cavities around these galaxies and their neighbours, stopping the infall of matter. In this way the hierarchical build-up process is halted; the brief phase of radio-activity (the "radio galaxy" phase) is indicative of feedback in action. Direct X-ray observations show us these cavities around radio AGN. I propose a combination of observations and analysis to examine the space densities of different types of radio AGN, to form a coherent scheme of how the radio phase manifests itself. Are the numbers adequate to produce the necessary feedback? What types of radio galaxy are most effective in this role, and can we relate their physics to that required by the feedback process? What is at stake is whether the hypothesis of feedback is consistent with modern data. The significance? Until such an analysis is carried through, our picture of galaxy formation - and indeed of our existence in galaxies - remains incomplete.

我们观察到，我们生活在一个由星系组成的宇宙中，星系是由数十亿颗恒星组成的庞大有序的集合体，其中许多恒星都有行星，至少有一颗行星上有生命。我们生活的“原因”是哲学、宗教;“它是如何发生的”是科学的领域。我们几个世纪的观察使我们对“如何”达成了当前的共识宇宙学;但这种共识宇宙学比小说还要奇怪。“怎么做”是这样的。我们早期宇宙中的微小波动，被认为是宇宙射电背景的印记，是更大和混乱的结构被引力收集的种子-早期星系。这些都是由恒星照亮的，恒星也是由引力形成的，大爆炸中产生的原始氢和氦气的丰富燃料坍缩形成了第一个核发电机。随着恒星轨道进入引力驱动的模式，星系逐渐长大并变得有序：通常是螺旋形或椭圆形。在引力等级中的聚集将这些星系安置成一个被称为“宇宙网”的设计，一个星系在星系团中的网络和细丝，其交叉点-节点-代表星系团。到了20世纪末，情况变得非常奇怪。获得诺贝尔奖的对遥远星系中超新星的观测迫使我们推断，我们的宇宙正在被一种神秘的“暗能量”加速。它的起源要么是简单的，作为广义相对论的可能结果，要么是复杂的，来自尚未构思的几何学和物理学。暗能量占宇宙质量的70%。另外25%是“暗物质”，我们还无法观察到的弱相互作用粒子。剩下的5%是我们所知道和喜爱的物质形式，我们，地球和我们的宇宙都是由重子组成的，构成标准的原子和分子。这是“Lambda CDM”宇宙学，Lambda描述了未知的加速剂，CDM是冷暗物质：我们宇宙的95%仍有待了解。在这样的宇宙中形成星系是一个棘手的平衡过程。LambdaCDM宇宙学邀请了宇宙网中星系的分级重力形成。但如果不加以控制，它就太成功了--我们周围的所有星系，即本星系，都应该是蓝色的，正在形成恒星，而且非常巨大。相反，他们通常是老的，“红色和死亡”，和小。有东西阻止了星系的形成。这种电荷现在被放置在射电活动星系核（radio Active Galactic Nuclei）的门口，射电活动星系核（radio Active Galactic Nuclei）是由来自中央超大质量黑洞（SMBH）的双相对论光束提供动力的双叶射电源。通过测量星系的旋转，我们知道大多数星系的中心都有一个黑洞，而大型星系则拥有SMBH。这些星系通过双喷射系统爆发出的能量可以在这些星系及其邻居周围雕刻出巨大的空腔，阻止物质的流入。通过这种方式，层次结构的建立过程停止了;放射性活动的短暂阶段（“射电星系”阶段）表明反馈正在起作用。直接的X射线观测向我们展示了射电活动星系核周围的空洞。我建议结合观测和分析来研究不同类型的射电活动星系核的空间密度，以形成一个关于射电相位如何表现自己的连贯方案。这些数字是否足以产生必要的反馈？什么类型的射电星系在这个角色中最有效，我们能把它们的物理学与反馈过程所需的联系起来吗？关键在于反馈的假设是否与现代数据相一致。意义？在进行这样的分析之前，我们关于星系形成的图像--实际上我们在星系中的存在--仍然是不完整的。