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Models of quasars. (English) Zbl 1257.85002

D’Onofrio, Mauro (ed.) et al., Fifty years of quasars. From early observations and ideas to future research. Berlin: Springer (ISBN 978-3-642-27563-0/hbk; 978-3-642-27564-7/ebook). Astrophysics and Space Science Library 386, 337-437 (2012).
Summary: At present, it is believed that all or most galaxies harbor a massive or even supermassive black hole in their nuclei. Sometimes gas finds its way close to and finally into the black hole. This process of accretion is thought to give rise to an active galactic nucleus and in extreme cases, a quasar. The most widely considered model then involves a black hole, an accretion disk, an obscuring torus (for unification), and, for radio-loud sources, very powerful relativistic radio jets. The questions of this chapter will be concerned with the structure and dynamics of the emitting regions and with the relationship to the central black hole parameters. We choose to focus on a few selected aspects for which the observational data have been extensively reported in previous chapters. The first discussion is on the theory of line formation, followed by an analysis of forces that may shape the profiles of emission lines. Going deeper toward the central black hole, questions address the origin of the thermal component of the continuum. A major topic are the physical processes that influence the dynamics of outflow and inflow. QSO outflows are extremely important because of their expected effects on the host galaxies. We first discuss winds and go on analyzing relativistic jets, one of the most extreme phenomena in astrophysics (and one that has proved to be among the most difficult to solve). The physical mechanism that can actualize the accretion paradigm, that is, the very inflow of matter onto the central black hole, need to be well understood before an exhaustive theory of nuclear activity can be formulated. A debated issue is how a molecular torus that is expected to obscure most quasars can preserve a significant geometrical thickness. In the end, we will speak about a phenomenological model that includes the structural elements and dynamical processes discussed in the chapter.
For the entire collection see [Zbl 1252.85003].

MSC:

85-02 Research exposition (monographs, survey articles) pertaining to astronomy and astrophysics
85A15 Galactic and stellar structure
85A25 Radiative transfer in astronomy and astrophysics
81T20 Quantum field theory on curved space or space-time backgrounds
83C55 Macroscopic interaction of the gravitational field with matter (hydrodynamics, etc.)
78A25 Electromagnetic theory (general)
83C57 Black holes
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