A Multiwavelength Study of the Physics of the Intracluster Medium, Its Multiple Phases and AGN Feedback

簇内介质物理、多相和 AGN 反馈的多波长研究

• 批准号: RGPIN-2017-04939
• 负责人: Baum, Stefi
• 金额: $ 1.53万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633449
• 关键词: Multiwavelength; Study; Physics; Intracluster; Medium

Clusters of galaxies are the largest gravitationally bound structures in the Universe. Baryonic matter, unlike the dominant dark matter, is accessible to direct observations. It is found within individual galaxies as stars and as a hot tenuous gas, dubbed the ICM, filling the space between galaxies. As the ICM cools it radiates in the x-ray part of the spectrum. Left unattended it will continue to cool, radiating in the ultraviolet, optical, and infrared. Ultimately the gas should cool to tens of degrees and be bound in giant molecular gas clouds that collapse to form stars. At the center of a rich cluster sits a massive bright elliptical galaxy, the Brightest Cluster Galaxy (BCG), which houses a super-massive Black Hole (SMBH) at its nucleus. It is believed that the SMBH re-supplies energy to the ICM as some of the cold gas that condenses from the ICM falls onto an accretion disk around the Black Hole, ultimately adding to the mass of the Black Hole and fuelling the ejection of a powerful outflow. This outflow carries energy, magnetic fields, and relativistic electrons into the ICM where it can re-supply energy lost through radiation. Recent observations with radio and X-ray telescopes have provided new high quality images showing the outflow excavating cavities and driving pressure waves into the ICM. Thus it is clear a complex interplay exists between cooling and heating, inflow and outflow, accretion and growth. The same physical processes operating in clusters today likely occurred during galaxy formation 5-10 billion years ago. Astronomers believe that the growth of the galaxy and its central black hole are coupled via feedback process. The feedback between the medium, galaxy growth, and the central black hole must operate over billions of years, and on size scales from parsecs to hundred of thousands of parsecs. Thus, the ICM is a dynamic place where heating and cooling processes vie for dominance, super-massive black holes grow at the centers of galaxies, and an uneasy equilibrium is maintained.

星系团是宇宙中最大的引力束缚结构。重子物质与占主导地位的暗物质不同，可以直接观测到。它在单个星系中被发现为恒星和热的稀薄气体，被称为ICM，充满星系之间的空间。 当ICM冷却时，它在光谱的X射线部分中辐射。如果无人看管，它将继续冷却，辐射紫外线，光学和红外线。最终，这些气体应该会冷却到几十度，并被束缚在巨大的分子气体云中，坍塌形成恒星。在一个丰富的星系团的中心，坐落着一个巨大的明亮的椭圆星系，布里渊星系团星系（BCG），它的核心有一个超大质量黑洞（SMBH）。 人们相信，SMBH重新提供能量给ICM，因为ICM凝结的一些冷气体福尔斯落在黑洞周围的吸积盘上，最终增加了黑洞的质量，并推动了强大的流出物的喷射。这种外流携带能量，磁场和相对论电子进入ICM，在那里它可以重新补充因辐射而损失的能量。无线电和X射线望远镜的最新观测提供了新的高质量图像，显示出外流挖掘洞穴和驱动压力波进入ICM。因此，很明显，在冷却和加热、流入和流出、吸积和生长之间存在着复杂的相互作用。今天在星系团中运行的相同物理过程可能发生在50亿至100亿年前的星系形成期间。天文学家认为，星系的增长和它的中心黑洞是通过反馈过程耦合的。 介质、星系生长和中心黑洞之间的反馈必须持续数十亿年，其规模从秒差距到数十万秒差距不等。 因此，ICM是一个动态的地方，加热和冷却过程争夺主导地位，超大质量黑洞在星系中心生长，并保持不稳定的平衡。