Why are only some supermassive black holes actively feeding as AGN?

为什么只有一些超大质量黑洞会以活动星系核的形式活跃地进食？

• 批准号: 2430048
• 金额: --
• 依托单位: University of Nottingham
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2430048
• 关键词: Why; only; some; supermassive; black

At the heart of most, if not all, massive galaxies lies a supermassive black hole (SMBH; Ferrarese & Ford, 2005, Space Sci. Rev.116, 523). SMBHs grow through the self-regulated accretion of material, during which time they present as active galactic nuclei (AGN) and release enormous amounts of radiative and mechanical energy. This energy impacts both their host galaxy, by driving gaseous outflows, and their larger environment through heating the surrounding intergalactic or intracluster medium. The ubiquity of SMBHs, however, contrasts with the paucity of AGN. Less than 10% of massive galaxies are AGN (Martini et al., 2013, ApJ, 768, 1), meaning that SMBHs lie in a dormant phase for most of their lifetime. This presents a conundrum as most massive galaxies have a ready supply of hot or cold gas which could feed the SMBH. Given the link between SMBH and galaxy growth (Ferrarese & Ford, 2005), as well as the devastating impact of AGN feedback on galaxy evolution (Bower et al. 2012, MNRAS, 422, 2816), our lack of understanding of what triggers AGN is a key unresolved issue in galactic astrophysics.The environment of AGN provides a fundamental test for a variety of AGN triggers (Haines et al., 2012; ApJ, 754,97). For example, if cold gas or galaxy mergers are required for nuclear activity then AGN should be distributed primarily in low mass groups and the filaments that feed into clusters. On the other hand, if nuclear activity is fuelled by hot gas we would expect AGN to be most prevalent in the core regions of groups and clusters. If AGN activity is a stochastic phenomenon, unrelated to environment, then we would expect the distribution of AGN to mirror that of star forming galaxies (their most common host galaxy). So far, the environment of AGN has been investigated in limited scope due to the expense of obtaining spectra and identifying AGN over wide areas. To solve this lack of data, the 1000-fibre-fed multi-object spectrograph (WEAVE) will be placed on the 4.2m William Herschel Telescope in La Palma in 2020. The forthcoming UK-led WEAVE-LOFAR (W-L) survey will use this instrument to gather more than a million spectra of active galaxies, including AGN. In this project you will use W-L to identify the precise environmental history of different types of AGN.

在大多数（如果不是全部的话）大质量星系的中心都有一个超大质量黑洞（SMBH; Ferrarese &福特，2005年，太空科学。Rev.116，523）。SMBH通过物质的自我调节吸积而生长，在此期间，它们以活动星系核（AGN）的形式存在，并释放出大量的辐射能和机械能。这种能量通过驱动气体外流来影响它们的宿主星系，并通过加热周围的星系际或星系团内介质来影响它们的更大环境。然而，SMBH的普遍存在与AGN的缺乏形成了鲜明对比。不到10%的大质量星系是活动星系核（Martini等人，2013，ApJ，768，1），这意味着SMBH在其生命的大部分时间处于休眠阶段。这是一个难题，因为大多数大质量星系都有现成的热或冷气体供应，可以为SMBH提供能量。考虑到SMBH和星系生长之间的联系（Ferrarese &福特，2005），以及AGN反馈对星系演化的破坏性影响（Bower et al. 2012，MNRAS，422，2816），我们对触发AGN的原因缺乏了解是星系天体物理学中一个关键的未解决问题。AGN的环境为各种AGN触发器提供了基本测试（Haines et al.，2012; ApJ，754，97）。例如，如果冷气体或星系合并是核活动所必需的，那么活动星系核应该主要分布在低质量的星系团和构成星系团的细丝中。另一方面，如果核活动是由热气体推动的，我们预计活动星系核将在星系团和星系团的核心区域最为普遍。如果活动星系核的活动是一种随机现象，与环境无关，那么我们可以预期活动星系核的分布会反映出形成星星的星系（它们最常见的宿主星系）的分布。迄今为止，由于在大范围内获取光谱和识别活动星系核的费用很高，活动星系核的环境研究一直局限在有限的范围内。为了解决这一数据缺乏的问题，1000光纤馈电的多目标光谱仪（WEAVE）将于2020年安装在位于拉帕尔马的4.2米威廉赫歇尔望远镜上。即将到来的英国主导的WEAVE-LOFAR（W-L）调查将使用该仪器收集超过一百万个活跃星系的光谱，包括AGN。在这个项目中，你将使用W-L来识别不同类型活动星系核的精确环境历史。