Black holes: sculptors of galaxies

点击翻译按钮获取中文摘要

One of the most fascinating discoveries in modern astrophysics has been the realization that all massive galaxies harbor a black hole at their centers - and that these black holes can be colossal, with masses readily exceeding a million Solar masses. When one such black hole is actively accreting matter from its surroundings, it can exhibit seemingly confounding properties. In particular, it can become so luminous as to outshine its host galaxy, and it can drive powerful outflows that often extend well beyond the galactic host. The interplay between the inflowing accreting matter versus the energy released through radiation and outflows (known as black hole feedback), plays a fundamental role in sculpting the surrounding environment of the black hole, and ultimately the host galaxy itself. Yet the details behind this exchange remain poorly understood. Accordingly, discerning the nature of this fundamental process is a forefront topic of research in modern astrophysics. The proposed program aims to significantly advance our understanding of black hole feedback in massive galaxies. The ultimate goal is to build a model of such feedback, which can then serve as a fundamental input for cosmological simulations. To accomplish this, we have built an extensive preliminary sample that encompasses a large range of massive galaxies with black hole outflows (>100 objects). This sample ranges from anemic isolated galaxies to the most massive galaxies known: those found at the centers of clusters of galaxies. These systems all have outflows in the form of “X-ray cavities” - gargantuan pits which are depleted of X-ray-emitting gas in the hot halos that surround massive galaxies - carved out by the outflows of the central black hole. Such targeted systems provide ample evidence in assessing the impact black holes have on their surrounding environment. In particular, X-ray cavities provide clean estimates for the energetics associated with black hole feedback; this is determined via straightforward calculations of the energy required to inflate them. By utilizing this sample, we will solve three key issues, with the long-term goal of building a model that describes how this feedback operates in massive galaxies - a model that will significantly benefit the extragalactic scientific community: (1) We will determine if the physical processes giving rise to black hole outflows are dependent upon galaxy mass. This touches upon questions such as, are outflows in smaller galaxies actually scaled-down versions of those found in the more massive systems? If not, why? How do AGN outflows depend on environmental effects or on the properties of their host galaxies? (2) We will determine if and how black hole feedback is capable of enriching the intergalactic medium by uplifting metal-rich gas beyond the confines of the host galaxies. This will be achieved by studying the elemental abundances surrounding the outflows. Quantifying the role AGN feedback plays in redistributing metal-rich gas, is vital to our general understanding of how galaxies form and evolve. (3) We will finally study the radiative properties directly arising from the black holes, providing insight into the black holes that power the outbursts. This includes building on our previous work on the fundamental plane of black hole activity, an established relation between X-ray luminosity, radio luminosity, and black hole mass, as well as building for the first time spectral energy distributions for these objects. The program will inform our general understanding of black hole physics, as well as have bearing in extragalactic astrophysics and cosmology.