AGN Outflows Research Articles

Winds and Outflows in Starburst Galaxies and AGN

Winds and outflows in starburst galaxies and AGN provide important information on the physics of the ‘central engine’, the presence and evolution of (nuclear) starbursts, and the metal enrichment of the nuclear environment and the intergalactic medium. Here, we concentrate on two examples, X-ray observations of the (U)LIRG NGC 6240 and the BAL quasar APM 08279+5255.

Hydromagnetic acceleration in relativistic outflows

We demonstrate that hydromagnetic acceleration can be the driving mechanism of relativistic outflows in AGNs as well as in Gamma-ray burst sources and Crab-like pulsars. Using semianalytical solutions of the full set of the steady, axisymmetric, ideal hydromagnetic equations in flat spacetime—i.e., solving the momentum equation along the flow as well as in the transfield direction—we model the acceleration of relativistic outflows. We find that a Poynting-flux dominated flow near the source reaches equipartition between matter and magnetic energy-fluxes, or even becomes completely matter-dominated (as in the case of Crab-like pulsar winds).

On the Column Density of AGN Outflows: The Case of NGC 5548

We reanalyze the Hubble Space Telescope high-resolution spectroscopic data of the intrinsic absorber in NGC 5548 and find that the C IV absorption column density is at least 4 times larger than previously determined. This increase arises from accounting for the kinematical nature of the absorber and from our conclusion that the outflow does not cover the narrow emission line region in this object. The improved column density determination begins to bridge the gap between the high column densities measured in the X-ray and the low ones previously inferred from the UV lines. Combined with our findings for outflows in high-luminosity quasars, these results suggest that traditional techniques for measuring column densities—equivalent width, curve of growth, and Gaussian modeling—are of limited value when applied to UV absorption associated with active galactic nucleus outflows.

Total Flux Density Variations in Extragalactic Radio Sources. III. Doppler Boosting Factors, Lorentz Factors, and Viewing Angles for Active Galactic Nuclei

We have calculated Doppler boosting factors, Dvar, for a sample of active galactic nuclei (AGNs) using total flux density variation monitoring data at 22 and 37 GHz. We argue that this method is more accurate than the other commonly used methods based on the synchrotron self-Compton X-ray flux or equipartition of energy. We compare our Doppler factors with other results and conclude that even if the average Dvar for a class of sources is very similar to all others, the variability Doppler factors for individual objects are more accurate and reliable. An important application of precise Doppler factors is presented, namely, calculating the Lorentz factors, Γ, and the viewing angles, θ, of relativistic outflows inAGNs. We find that high-polarization quasars have the greatest Doppler boosting, while low-polarizationquasars and BL Lac objects are less boosted. The two groups of quasars show different characteristics because of different combinations of the Lorentz factor and viewing angle, rather than either a different Γ or θ alone.

The Dynamics and Radiative Properties of Clouds in Magnetized Accretion Disk Outflows in AGNs

AbstractWe 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 disc surface, taking account of the radiation pressure force exerted by the central continuum for different spectral energy distributions and emission patterns. We study the evolution of the clouds as they accelerate through the wind, considering possible sources of confinement and estimating the cloud lifetimes against various disruptive processes. We then examine the spectral signatures of accelerated clouds in the context of this dynamical scheme and compute absorption line profiles 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, as well as to other AGNs in which radiative acceleration of clouds has been inferred (e.g., “warm absorbers”).

Non‐stationary Accretion With Ordered Magnetic Fields and Outflows in AGNs and Quasars*

Non‐stationary Accretion With Ordered Magnetic Fields and Outflows in AGNs and Quasars*