31 research outputs found
The line parameters and ratios as the physical probe of the line emitting regions in AGN
Here we discuss the physical conditions in the emission line regions (ELR) of
active galactic nuclei (AGN), with the special emphasize on the unresolved
problems, e.g. the stratification of the Broad Line Region (BLR) or the failure
of the photoionization to explain the strong observed optical Fe II emission.
We use here different line fluxes in order to probe the properties of the ELR,
such as the hydrogen Balmer lines (Ha to He), the helium lines from two
subsequent ionization levels (He II 4686 and He I 5876) and the strongest Fe II
lines in the wavelength interval 4400-5400 \AA. We found that the hydrogen
Balmer and helium lines can be used for the estimates of the physical
parameters of the BLR, and we show that the Fe II emission is mostly emitted
from an intermediate line region (ILR), that is located further away from the
central continuum source than the BLR.Comment: 8 pages, 9 figures, 2 tables, New Astronomy Reviews (Proceeding of
7th SCSLSA), in pres
Long term variability of the Broad Emission Line profiles in AGN
Results of a long-term monitoring ( years) of the broad line and
continuum fluxes of three Active Galactic Nuclei (AGN), 3C 390.3, NGC 4151, and
NGC 5548, are presented. We analyze the H and H profile
variations during the monitoring period and study different details (as bumps,
absorption bands) which can indicate structural changes in the Broad Line
Region (BLR). The BLR dimensions are estimated using the time lags between the
continuum and the broad lines flux variations. We find that in the case of 3C
390.3 and NGC 5548 a disk geometry can explain both the broad line profiles and
their flux variations, while the BLR of NGC 4151 seems more complex and is
probably composed of two or three kinematically different regions.Comment: 10 pages, 9 figures, New Astronomy Reviews (Proceeding of 7th
SCSLSA), in pres
Atomic data and electron-impact broadening effect in DO white dwarf atmospheres: Si VI
Energy levels, electric dipole transition probabilities and oscillator
strengths in five times ionized silicon have been calculated in intermediate
coupling. The present calculations were carried out with the general purpose
atomic-structure program SUPERSTRUCTURE. The relativistic corrections to the
non-relativistic Hamiltonian are taken into account through the Breit-Pauli
approximation. We have also introduced a semi-empirical correction (TEC) for
the calculation of the energy-levels. These atomic data are used to provide
semiclassical electron-, proton- and ionized helium- impact line widths and
shifts for 15 Si VI muliplet. Calculated results have been used to consider the
influence of Stark broadening for DO white dwarf atmospheric conditions.Comment: MNRAS, accepted, 14 page
Supermassive Black Hole Binaries: The Search Continues
Gravitationally bound supermassive black hole binaries (SBHBs) are thought to
be a natural product of galactic mergers and growth of the large scale
structure in the universe. They however remain observationally elusive, thus
raising a question about characteristic observational signatures associated
with these systems. In this conference proceeding I discuss current theoretical
understanding and latest advances and prospects in observational searches for
SBHBs.Comment: 17 pages, 4 figures. To appear in the Proceedings of 2014 Sant Cugat
Forum on Astrophysics. Astrophysics and Space Science Proceedings, ed.
C.Sopuerta (Berlin: Springer-Verlag
Active Galactic Nuclei at the Crossroads of Astrophysics
Over the last five decades, AGN studies have produced a number of spectacular
examples of synergies and multifaceted approaches in astrophysics. The field of
AGN research now spans the entire spectral range and covers more than twelve
orders of magnitude in the spatial and temporal domains. The next generation of
astrophysical facilities will open up new possibilities for AGN studies,
especially in the areas of high-resolution and high-fidelity imaging and
spectroscopy of nuclear regions in the X-ray, optical, and radio bands. These
studies will address in detail a number of critical issues in AGN research such
as processes in the immediate vicinity of supermassive black holes, physical
conditions of broad-line and narrow-line regions, formation and evolution of
accretion disks and relativistic outflows, and the connection between nuclear
activity and galaxy evolution.Comment: 16 pages, 5 figures; review contribution; "Exploring the Cosmic
Frontier: Astrophysical Instruments for the 21st Century", ESO Astrophysical
Symposia Serie
Atomic data estimation for H and C IV transitions in strong gravitation field
The gravitational field effect on atomic data for H and C IV transitions are
considered as a perturbation of initial and final energy levels. We found
that this perturbation increases with the principal quantum number. Here we
give several expressions for estimation of this effect and its influence on
atomic data parameters. Also, the calculations of atomic data for 1s − 2p
(Lyα) and 2s − 3p transitions of hydrogen atom as well as atomic data for
2s2S1/2−2p2P0 1/2,3/2 transitions of C IV (1UV) as a function of deformation
of energy levels due to gravitation field and gravitational redshift are
given. The gravitational field effect should be estimated and should be taken
into account in calculation of atomic data for emitters in Broad Line Regions
(BLRs) of Active Galactic Nuclei (AGN)
Estimation of electron-impact line widths for singly-, doubly- and triply-charged vanadium ions
In this paper we present the electron-impact widths for 28 transitions of
singly-, doubly-, and triply- ionized vanadium estimated by using the
modified semiempirical method. The electron-impact widths have been estimated
for the electron density of 1023m−3 and presented as a function of electron
temperature
Stark broadening parameter tables for Kr II lines
In order to provide the Stark broadening data for ion lines from complex spectra, here we present calculated Stark widths and shifts for 37 Kr II lines. The calculations were performed by using the modified semiempirical approach. Also the obtained results have been compared with existing experimental and theoretical data
Can double-peaked lines indicate merging effects in AGNs?
The influence of merging effects in the central part of an Active Galactic Nucleus (AGN) on the emission spectral line shapes are discussed. We present a model of close binary Broad Line Region. The numerical experiments show that the merging effects can explain double peaked lines. The merging effects may also be present in the center of AGNs, although they emit slightly asymmetric as well as symmetric and relatively stable (in profile shape) spectral lines. Depending on the black hole masses and their orbit elements such model may explain some of the line profile shapes observed in AGNs. This work shows that if one is looking for the merging effects in the central region as well as in the wide field structure of AGNs, he should first pay attention to objects which have double peaked lines