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Matter
Outflow from Active Galactic Nuclei
The subject of this work is the role of the massive stellar cluster in the activity phenomenon and in the structure of active galactic nuclei. We introduce a simple model of stellar dynamics in the internal part of the cluster, which allows us to include both the star-disk and the star-star interactions. It is shown that the properties of the distribution of stars in the vicinity of the black hole are determined both by the interaction of the stars with the accretion disk and by the pair gravitational and contact interaction between the stars. We calculate the distribution of stars in the central parts of the cluster and we discuss possible effects of stellar mass-loss due to the star-disk interaction. Finally, we study the implications of the central cluster for active galactic nuclei activity. We model the broad line region assuming that the gaseous wakes, following stars after each disk crossing, play the role of the broad line region clouds, and we calculate the corresponding line profiles. We also analyze the contribution of star-star and star-disk collisions to active galactic nuclei variability.
A recently taken WHT optical spectrum of the BAL QSO Q13031308 shows interesting changes in the spectral characteristics of the absorption systems. In particular, the equivalent widths of many of the broad absorption lines have markedly increased with respect to observations taken 15 yr earlier by Foltz et al., with the more blueshifted components showing the greatest increase by a factor of <5 in optical depth. Perhaps the most remarkable feature of the data is that, in the rest frame of the quasar, the line-of-sight outflow velocity of the clouds has only increased by <55 km/s in a rest-frame time interval of 5±6 yr. Various examples of doublet line locking are still visible in the system, and we present a provisional model analysis of the spectrum showing that theories based on small cloud velocity interactions via line locking can successfully explain the general appearance of the spectrum and its variability. Finally we highlight the need for further ongoing monitoring of this fascinating object.
The theory of broad-absorption-line (BAL) QSOs is worked out on the basis of the radiation hydrodynamics equation solution for the two-phase media of active galactic nuclei. We suppose that the BAL QSO physics depends on some `hidden' AGN parameters, such as the mass and size of the compact stellar system. We therefore approach this problem in the more general framework of the `interacting subsystems theory', which includes these parameters. We compare the results of the numerical model calculations with the observed spectra and show that the BAL QSOs (and the radio-quiet quasars as well) contain massive compact stellar kernels in their central regions. We show that the line-locking effect is determined by the radiation pressure, and is also favoured by the drag force of the hot gas acting on the line-absorbing clouds. We derive some general conclusions about the physics of AGN. In particular, we show that the radio-quiet versus radio-loud dichotomy can be explained by using two types of hot gas outstreams in quasars.
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The
role of the central stellar cluster in active galactic nuclei. 