Towards a comprehensive understanding of the interstellar medium in the extreme environment of Active Galactic Nuclei

全面了解活动星系核极端环境下的星际介质

• 批准号: 263101211
• 负责人: Dr. Leonard Burtscher
• 金额: --
• 依托单位: Max-Planck-Institut für extraterrestrische Physik (MPE)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/263101211?language=en
• 关键词: Towards; comprehensive; understanding; interstellar; medium

A fundamental role is attributed to supermassive black holes in the evolution of galaxies. But theoretical models trying to reproduce the relation between black hole mass and stellar velocity dispersion and other relations, have to make broad assumptions about the physical processes involved, and the prescriptions used are poorly constrained. The implementation of AGN feeding and feedback in models remains simplistic because observations have focussed on the question of where the inflowing material originates - mergers versus secular evolution - and on integrated galaxy properties.In contrast, there is now an increasing realisation that AGN activity may be flickering on timescales as short as a few million years and that the feeding must therefore be governed by processes on the 10 - 100 pc scale. Our popular evolutionary starburst model describes AGN activity as a time-sequence where (1) cold gas inflows lead to a nuclear starburst that soon (2) stirs the ISM (via exploding type II supernovae) and prevents the gas from cooling. Only after this violent phase has ended (3), do stellar winds from evolved stars inject new mass into the nuclear ISM. The angular momentum of the ejected material dissipates in collisions and a stable accretion flow forms - the AGN lights up. Initial observational and theoretical studies have suggested that such a connection could exist.Yet these nuclear processes have not been systematically studied, since the detailed research necessary was focused on individual well-known galaxies instead of the population as a whole. To remedy this, we will address the physical properties of the ISM in a complete sample of the most powerful local AGNs and compare them with an equally large sample of inactive galaxies, carefully matched in distance, mass, inclination and large-scale galaxy properties (Hubble type, prevalence of bar).In order to gather a comprehensive understanding of the feeding and feedback of AGNs we have already begun observing the 20 most luminous local AGNs as well as the control sample. Using VLT/SINFONI integral field spectroscopy in the H+K bands we will determine the dynamics of the stars and gas; high resolution and high quality VLT/XSHOOTER spectroscopy from the UV to the NIR will give us unprecedented leverage to determine the stellar populations and infer their impact on the ISM. Finally, observations of multiple molecular gas transitions of several species will allow us to determine directly the physical conditions of the gas in both active and inactive nuclei.Our novel approach brings together the multi-scale and multi-wavelength observational evidence. In combination with our hydrodynamical models, that are ready to be used, it will allow us to establish a solid statistical basis for understanding the differences in the physical conditions of the ISM in AGNs and inactive galaxies on the scales that are directly relevant to accretion onto the central supermassive black hole.

超大质量黑洞在星系演化中起到了重要作用。但是，试图重现黑洞质量和恒星速度色散之间的关系以及其他关系的理论模型，不得不对所涉及的物理过程做出广泛的假设，而且所用的处方约束很差。在模型中实施活动星系核的馈送和反馈仍然是简单的，因为观测的重点是流入物质的来源问题--合并和长期演化--以及星系的综合性质。相比之下，现在越来越多的人意识到，活动星系核的活动可能在短至几百万年的时间尺度上闪烁，因此馈送必须由10-100pC尺度的过程控制。我们流行的演化星暴模型将活动星系核的活动描述为一个时间序列，其中(1)冷气体流入导致核星暴，并很快(2)通过爆炸的II型超新星搅动ISM并阻止气体冷却。只有在这个激烈的阶段结束后(3)，演化恒星的恒星风才会为核ISM注入新的质量。被抛出的物质的角动量在碰撞中消散，形成稳定的吸积流-活动星系核点亮。最初的观测和理论研究表明，这种联系是可能存在的。然而，这些核过程还没有得到系统的研究，因为所需的详细研究集中在个别著名的星系，而不是整个星系群。为了纠正这一点，我们将在一个最强大的局部活动星系核的完整样本中解决ISM的物理性质，并将它们与一个同样大的不活动星系的样本进行比较，这些星系在距离、质量、倾斜度和大型星系属性(哈勃类型、棒条的流行程度)方面都是仔细匹配的。为了收集对活动星系核的馈送和反馈的全面了解，我们已经开始观测20个最明亮的局部活动星系核以及对照样本。利用H+K波段的VLT/SINFONI积分场光谱，我们将确定恒星和气体的动力学；从UV到NIR的高分辨率和高质量的VLT/xShooter光谱将给我们前所未有的杠杆作用来确定恒星的数量并推断它们对ISM的影响。最后，对几个物种的多分子气体跃迁的观测将使我们能够直接确定活跃核和非活跃核中气体的物理条件。我们的新方法结合了多尺度和多波长的观测证据。结合我们已准备好使用的流体动力学模型，它将使我们能够建立坚实的统计学基础，以了解活动星系核和非活动星系在尺度上的ISM物理条件的差异，这些差异与中心超大质量黑洞的吸积直接相关。