129 research outputs found
Vertical broad-line region structure in nearby active galactic nuclei
Broad emission lines are emitted in the surroundings of supermassive black
holes in the centers of active galactic nuclei (AGN). This region is spatially
not resolved. We intend to get information on the structure and geometry of
this broad emitting line region (BLR) based on line profile observations. We
model the rotational and turbulent velocities in the line-emitting regions
based on observed full-width at half maximum line values (FWHM) and
{\sigma}_{line} of the variable broad emission lines in four nearby AGN: NGC
3783, NGC 7469, NGC 5548, and 3C 390.3. On the basis of these velocities, we
estimate the height of the line-emitting regions above the midplane in context
with their distances from the center. The H{\beta} lines are emitted in a more
flattened configuration above the midplane in comparison to the highly ionized
lines. The H{\beta} lines originate at heights of 0.7 to 1.6 light-days and at
distances of 1.4 to 24 light-days with height/distance (H/R) ratios of only
0.07 to 0.5. The highly ionized lines originate at smaller radii than the
H{\beta} lines and/or at greater distances above the midplane with H/R values
of 0.2 to 1.7. In total, the emission lines do not originate in a thin
atmosphere of an accretion disk but rather at very extended regions above an
accretion disk. The observed geometries of the line-emitting regions resemble
the geometries of accretion disk wind models. Furthermore, the angle of the
central opening cone (generated by the emitting regions of the highly ionized
lines) is small for those galaxies with slow rotational velocities and
increases with the rotation velocity of the central region. The derived
geometries of the line-emitting regions of all four AGN are consistent with the
geometries that are predicted in outflowing disk wind models.Comment: 12 pages, 18 figures, Astronomy & Astrophysics in pres
The shape of broad-line profiles in AGN
We present a study of the broad optical/UV emission line profiles in AGN
(active galactic nuclei) to get information on the dominant velocity components
(turbulence, rotation, etc.) in the central broad-line region (BLR). We
introduce line broadening simulations of emission line profiles and compare
these results with the largest homogeneous data set of reverberation-mapped
AGN. The underlying broad-line profiles in AGN are Lorentzian profiles caused
by turbulence in the line emitting region. The turbulent velocities are
different for the different line emitting regions of Ha, Hg, Lya, CIII] 1909,
He II 1640, and Si IV 1400. The turbulent velocities go from 400 km/s for Hb up
to 3,800 km/s for Lya+Nv 1240. The dominating broadening mechanism of these
profiles is broadening due to rotation. The rotation velocities causing the
line profile broadening go from 500 km/s up to 6,500 km/s. Here we present
interrelations between observed emission line widths (FWHM) and their related
rotational velocities to correct for the contribution of the turbulence to the
broad-line profiles.Comment: 10 pages, 19 figures, to be published in A&
Accretion disk wind as explanation for the broad-line region structure in NGC 5548
Supermassive black holes in the centers of active galactic nuclei (AGN) are
surrounded by broad-line regions (BLRs). The broad emission lines seen in the
AGN spectra are emitted in this spatially unresolved region. We intend to
obtain information on the structure and geometry of this BLR based on observed
line profiles. We modeled the rotational and turbulent velocities in the
line-emitting region on the basis of the line-width FWHM and line dispersion
sigma_line of the variable broad emission lines in NGC5548. Based on these
velocities we estimated the height of the line-emitting regions above the
midplane in the context of their distances from the center. The broad emission
lines originate at distances of 2 to 27 light days from the center. Higher
ionized lines originate in the inner region (lesser equal 13 light days) in
specific filamentary structures 1 to 14 light days above the midplane. In
contrast, the Hbeta line is emitted in an outer (6 - 26 light days), more
flattened configuration at heights of 0.7 to 4 light days only above the
midplane. The derived geometry of the line-emitting region in NGC5548 is
consistent with an outflowing wind launched from an accretion disk.Comment: 4 pages, 5 figures, Astron. & Astrophys. Letter, in pres
The environment of AGNs and the activity degree of their surrounding galaxies
Aims. We present results of a comprehensive spectral study on the large-scale
environment of AGNs based on Sloan Spectroscopic Survey data. Methods. We
analyzed the spectra of galaxies in the environment of AGN and other activity
classes up to distances of 1 Mpc. Results. The mean H{\alpha} and [OIII]
{\lambda}5007 line luminosities in the environmental galaxies within a
projected radius of 1 Mpc are highest around Seyfert 1 galaxies, with
decreasing luminosities for Seyfert 2 and HII galaxies, and lowest for
absorption line galaxies. Furthermore, there is a trend toward H{\alpha} and
[OIII] luminosities in the environmental galaxies increasing as a function of
proximity to the central emission line galaxies. There is another clear trend
toward a neighborhood effect within a radius of 1000 kpc for the AGN and
non-AGN types: Seyfert galaxies tend to have the highest probability of having
another Seyfert galaxy in the neighborhood. HII galaxies tend to have the
highest probability of having another HII galaxy in the neighborhood, etc. The
number of companions within 1000 kpc is inversely correlated with the
H{\alpha}, [OIII] {\lambda}5007, as well as with the continuum luminosities of
the central galaxies, regardless of whether they are of Seyfert, HII, or
absorption line types.Comment: 9 pages, 6 figures, to be published in A&
Broad-line region structure and kinematics in the radio galaxy 3C 120
Broad emission lines originate in the surroundings of supermassive black
holes in the centers of active galactic nuclei (AGN). One method to investigate
the extent, structure, and kinematics of the BLR is to study the continuum and
line profile variability in AGN. We selected the radio-loud Seyfert 1 galaxy 3C
120 as a target for this study. We took spectra with a high signal-to-noise
ratio of 3C 120 with the 9.2m Hobby-Eberly Telescope between Sept. 2008 and
March 2009. In parallel, we photometrically monitored the continuum flux at the
Wise observatory. We analyzed the continuum and line profile variations in
detail (1D and 2D reverberation mapping) and modeled the geometry of the
line-emitting regions based on the line profiles. We show that the BLR in 3C
120 is stratified with respect to the distance of the line-emitting regions
from the center with respect to the line widths (FWHM) of the rms profiles and
with respect to the variability amplitude of the emission lines. The emission
line wings of H{\alpha} and H{\beta} respond much faster than their central
region. This is explained by accretion disk models. In addition, these lines
show a stronger response in the red wings. However, the velocity-delay maps of
the helium lines show a stronger response in the blue wing. Furthermore, the
HeII{\lambda}4686 line responds faster in the blue wing in contradiction to
observations made one and a half years later when the galaxy was in a lower
state. The faster response in the blue wing is an indication for central
outflow motions when this galaxy was in a bright state during our observations.
The vertical BLR structure in 3C 120 coincides with that of other AGN. We
confirm the general trend: the emission lines of narrow line AGN originate at
larger distances from the midplane than AGN with broader emission lines.Comment: 18 pages, 25 figures, Astronomy & Astrophysics in pres
Proving strong magnetic fields near to the central black hole in the quasar PG0043+039 via cyclotron lines
The optical luminous quasar PG0043+039 has not been detected before in deep
X-ray observations indicating the most extreme optical-to-X-ray slope index
of all quasars. This study aims to detect PG0043+039 in a deep
X-ray exposure. Furthermore, we wanted to check out whether this object shows
specific spectral properties in other frequency bands. We took deep X-ray
(XMM-Newton), far-ultraviolet (HST), and optical (HET, SALT telescopes) spectra
of PG0043+039 simultaneously in July 2013. We just detected PG0043+039 in our
deep X-ray exposure. The steep gradient is
consistent with an unusual steep gradient with
seen in the UV/far-UV continuum. The optical/UV
continuum flux has a clear maximum near 2500 {\AA}. The UV spectrum is very
peculiar because it shows broad humps in addition to known emission lines. A
modeling of these observed humps with cyclotron lines can explain their
wavelength positions, their relative distances, and their relative intensities.
We derive plasma temperatures of T 3keV and magnetic field strengths
of B 2 G for the line-emitting regions close to the
black hole.Comment: 4 pages, 3 figures, Astronomy & Astrophysics in pres
The broad-line region and dust torus size of the Seyfert 1 galaxy PGC50427
We present the results of a three years monitoring campaigns of the type-1 active galactic nucleus (AGN) PGC50427. Through the use of
Photometric Reverberation Mapping with broad and narrow band filters, we
determine the size of the broad-line emitting region by measuring the time
delay between the variability of the continuum and the H emission line.
The H emission line responds to blue continuum variations with an
average rest frame lag of days. Using single epoch spectroscopy
we determined a broad-line H velocity width of 1020 km s and in
combination with the rest frame lag and adoption a geometric scaling factor , we calculate a black hole mass of . Using the flux variation gradient method, we separate the host
galaxy contribution from that of the AGN to calculate the rest frame 5100\AA~
luminosity at the time of our monitoring campaign. The rest frame lag and the
host-subtracted luminosity permit us to derive the position of PGC50427 in the
BLR size -- AGN luminosity diagram, which is remarkably close to the
theoretically expected relation of . The simultaneous
optical and NIR ( and ) observations allow us to determine the size
of the dust torus through the use of dust reverberation mapping method. We find
that the hot dust emission () lags the optical variations with an
average rest frame lag of days. The dust reverberation radius
and the nuclear NIR luminosity permit us to derive the position of PGC50427 on
the known diagram. The simultaneus observations for the
broad-line region and dust thermal emission demonstrate that the innermost dust
torus is located outside the BLR in PGC50427, supporting the unified scheme for
AGNs. (Abstract shortened, see the manuscript.)Comment: 11 pages, 23 figures, accepted for publication in Astronomy and
Astrophysic
Long-term optical, UV, and X-ray continuum variations in the changing-look AGN HE 1136-2304
A strong outburst in the X-ray continuum and a change of its Seyfert spectral
type was detected in HE 1136-2304 in 2014. The spectral type changed from
nearly Seyfert 2 type (1.95) to Seyfert 1.5 type in comparison to previous
observations taken ten to twenty years before. In a subsequent variability
campaign we wanted to investigate whether this outburst was a single event or
whether the variability pattern following the outburst was similar to those
seen in other variable Seyfert galaxies. In addition to a SALT spectral
variability campaign, we carried out optical continuum as well as X-ray and UV
(Swift) monitoring studies from 2014 to 2017. HE 1136-2304 strongly varied on
timescales of days to months from 2014 to 2017. No systematic trends were found
in the variability behavior following the outburst in 2014. A general decrease
in flux would have been expected for a tidal disruption event. This could not
be confirmed. More likely the flux variations are connected to irregular
fluctuations in the accretion rate. The strongest variability amplitudes have
been found in the X-ray regime: HE 1136-2304 varied by a factor of eight during
2015. The amplitudes of the continuum variability (from the UV to the optical)
systematically decreased with wavelength following a power law F_var = a
{\lambda}^-c with c = 0.84. There is a trend that the B-band
continuum shows a delay of three light days with respect to the variable X-ray
flux. The Seyfert type 1.5 did not change despite the strong continuum
variations for the period between 2014 and 2017.Comment: 25 pages, 21 figures, Astronomy & Astrophysics in pres
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