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Session 4 - Low Luminosity AGN and Starburst Galaxies.
Display session, Monday, June 10
We have embarked on a general analysis of multi-component outflows from magnetized accretion disks in AGNs. In this scenario, dense diamagnetic clouds are embedded in a centrifugally driven wind and are uplifted from the disk surface by the dynamical drag of the wind as well as by the ``melon seed'' magnetic pressure gradient force. We follow the motion of the clouds above the disk surface, taking account of the radiation pressure force exerted by the central continuum. We consider both line and continuum radiation and investigate the effects of differing spectral energy distributions and degrees of emission isotropy on the cloud dynamics (comparing, e.g., the isotropic, thermal emission from QSOs with the beamed, nonthermal emission from a relativistic jet in BL Lac objects). We study the evolution of the clouds as they accelerate through the wind, considering possible sources of confinement (including magnetic stresses of the ambient field and hydrodynamic ram pressure), and estimating the cloud lifetimes against disruptive processes such as evaporation and dynamical instabilities. We also evaluate the impact of radiation pressure on the wind itself, via the force on dust grains in the wind and through the momentum transferred by the clouds.
We examine the spectral signatures of accelerated clouds in the context of this dynamical scheme. Using the calculated velocity and ionization structure of the clouds throughout the flow, we compute absorption line profiles in the AGN continuum spectrum as a function of viewing angle through the wind. We apply our results to the interpretation of the observed optical/UV spectra from BALQSOs, and of the broad EUV and X-ray absorption features detected in a number of BL Lac objects. We also consider possible applications to other AGNs in which radiative acceleration of clouds has been inferred (e.g., ``warm absorber'' sources).
Program listing for Monday