Computer Science – Graphics
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21535906f&link_type=abstract
American Astronomical Society, AAS Meeting #215, #359.06; Bulletin of the American Astronomical Society, Vol. 42, p.546
Computer Science
Graphics
Scientific paper
We consider a two-dimensional steady-state, axisymmetric magnetohydrodynamic (MHD) accretion-disk wind as X-ray absorbing outflows, often found in active galactic nuclei (AGNs) and galactic black hole candidates (GBHCs). In this model a fraction of accreting plasma is assumed to be launched from the thin-disk surface with the Keplerian rotational velocity and magnetocentrifugally accelerated along magnetic field lines, as suggested in some sources (e.g. NGC 4151; GRO J1655-40). A central X-ray point-source is assumed to irradiate the wind being progressively absorbed as the radiation transmits through the line-of-sight (LOS) plasma. By coupling to the kinematic properties of the obtained hydromagnetic winds (e.g. geometry, density, velocity) we proceed with XSTAR photoionization code to handle radiative transfer along the LOS medium and compute the ionization structure of the wind. Our model, for a given density profile such as n(r) 1/r (where r is the LOS distance), is successful in reproducing the observed ionic column density distribution, the so called "absorption measure distribution (AMD)", which is found to be nearly constant (independent) over a large span of ionization parameter xi ( 4-5 orders of magnitudes) at the observed integrated column density, for instance, for IRAS 13349+2438. Our model can further reproduce the observed (blueshifted) LOS velocities for some characteristic ions; e.g. 100-300 km/s at log(xi) 2-3 for Fe XVII and 1,000-4,000 km/s at log(xi) 4-5 for Fe XXV, also in good agreement with Chandra data for IRAS 13349+2438, while this model can in principle allow for even higher LOS velocities relevant for some quasars (e.g. PDS 456; PG 1211+143). Model absorption lines are also simulated. Using our model that is characterized by only two parameters (mass-accretion rate and LOS angle) we demonstrate that a combination of AMD and absorption line profile observations can uniquely determine these model parameters and their bearing on AGN population demographics.
Behar Ehud
Contopoulos Ioannis
Fukumura Keigo
Kazanas Demos
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