45 research outputs found
Magnetic fields of active galactic nuclei and quasars with polarized broad H-alpha lines
We present estimates of magnetic field in a number of AGNs from the
Spectropolarimetric atlas of Smith, Young & Robinson (2002) from the observed
degrees of linear polarization and the positional angles of spectral lines
(H-alpha) (broad line regions of AGNs) and nearby continuum. The observed
polarization is lower than the Milne value in a non-magnetized atmosphere. We
hypothesize that the polarized radiation escapes from optically thick
magnetized accretion discs and is weakened by the Faraday rotation effect. This
effect is able to explain both the value of the polarization and the position
angle. We estimate the required magnetic field in the broad line region by
using simple asymptotic analytical formulas for Milne's problem in magnetized
atmosphere, which take into account the last scattering of radiation before
escaping from the accretion disc. The polarization of a broad spectral line
escaping from disc is described by the same mechanism. The characteristic
features of polarization of a broad line is the minimum of the degree of
polarization in the center of the line and continuous rotation of the position
angle from one wing to another. These effects can be explained by existence of
clouds in the left (velocity is directed to an observer) and the right
(velocity is directed from an observer) parts of the orbit in a rotating
keplerian magnetized accretion disc. The base of explanation is existence of
azimuthal magnetic field in the orbit. The existence of normal component of
magnetic field makes the picture of polarization asymmetric. The existence of
clouds in left and right parts of the orbit with different emissions also give
the contribution in asymmetry effect. Assuming a power-law dependence of the
magnetic field inside the disc, we obtain the estimate of the magnetic field
strength at first stable orbit near the central SMBH for a number of AGNs.Comment: 15 pages, 4 figure
Matter in Strong Magnetic Fields
The properties of matter are significantly modified by strong magnetic
fields, Gauss (), as are typically
found on the surfaces of neutron stars. In such strong magnetic fields, the
Coulomb force on an electron acts as a small perturbation compared to the
magnetic force. The strong field condition can also be mimicked in laboratory
semiconductors. Because of the strong magnetic confinement of electrons
perpendicular to the field, atoms attain a much greater binding energy compared
to the zero-field case, and various other bound states become possible,
including molecular chains and three-dimensional condensed matter. This article
reviews the electronic structure of atoms, molecules and bulk matter, as well
as the thermodynamic properties of dense plasma, in strong magnetic fields,
. The focus is on the basic physical pictures and
approximate scaling relations, although various theoretical approaches and
numerical results are also discussed. For the neutron star surface composed of
light elements such as hydrogen or helium, the outermost layer constitutes a
nondegenerate, partially ionized Coulomb plasma if , and may be in
the form of a condensed liquid if the magnetic field is stronger (and
temperature K). For the iron surface, the outermost layer of the
neutron star can be in a gaseous or a condensed phase depending on the cohesive
property of the iron condensate.Comment: 45 pages with 9 figures. Many small additions/changes. Accepted for
publication in Rev. Mod. Phy