87 research outputs found
The intrinsic Baldwin effect in broad Balmer lines of six long-term monitored AGNs
We investigate the intrinsic Baldwin effect (Beff) of the broad H and
H emission lines for six Type 1 active galactic nuclei (AGNs) with
different broad line characteristics: two Seyfert 1 (NGC 4151 and NGC 5548),
two AGNs with double-peaked broad line profiles (3C 390.3 and Arp 102B), one
narrow line Seyfert 1 (Ark 564), and one high-luminosity quasar with highly red
asymmetric broad line profiles (E1821+643). We found that a significant
intrinsic Beff was present in all Type 1 AGNs in our sample. Moreover, we do
not see strong difference in intrinsic Beff slopes in different types of AGNs
which probably have different physical properties, such as inclination, broad
line region geometry, or accretion rate. Additionally, we found that the
intrinsic Beff was not connected with the global one, which, instead, could not
be detected in the broad H or H emission lines. In the case of
NGC 4151, the detected variation of the Beff slope could be due to the change
in the site of line formation in the BLR. Finally, the intrinsic Beff might be
caused by the additional optical continuum component that is not part of the
ionization continuum.Comment: 12 pages, 8 figures, Accepted for publication in A&
Spectral optical monitoring of 3C390.3 in 1995-2007: I. Light curves and flux variation of the continuum and broad lines
Here we present the results of the long-term (1995-2007) spectral monitoring
of the broad line radio galaxy \object{3C~390.3}, a well known AGN with the
double peaked broad emission lines, usually assumed to be emitted from an
accretion disk. To explore dimensions and structure of the BLR, we analyze the
light curves of the broad H and H line fluxes and the continuum
flux. In order to find changes in the BLR, we analyze the H and
H line profiles, as well as the change in the line profiles during the
monitoring period. First we try to find a periodicity in the continuum and
H light curves, finding that there is a good chance for quasi-periodical
oscillations. Using the line shapes and their characteristics (as e.g. peaks
separation and their intensity ratio, or FWHM) of broad H and H
lines, we discuss the structure of the BLR. Also, we cross-correlate the
continuum flux with H and H lines to find dimensions of the BLR.
We found that during the monitoring period the broad emission component of the
H and H lines, and the continuum flux varied by a factor of
4-5. Also, we detected different structure in the line profiles of
H and H. It seems that an additional central component is
present and superposed to the disk emission. In the period of high activity
(after 2002), H became broader than H and red wing of H
was higher than the one of H. We found time lags of 95 days
between the continuum and H flux, and about 120 days between the
continuum and H flux. Variation in the line profiles, as well as
correlation between the line and continuum flux during the monitoring period is
in the favor of the disk origin of the broad lines with the possible
contribution of some additional region and/or some kind of perturbation in the
disk.Comment: 32 pages, accepted to A&A, typos correcte
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 monitoring of the broad-line region properties in a selected sample of AGN
We present the results of the long-term optical monitoring campaign of active
galactic nuclei (AGN) coordinated by the Special Astrophysical Observatory of
the Russian Academy of Science. This campaign has produced a remarkable set of
optical spectra, since we have monitored for several decades different types of
broad-line (type 1) AGN, from a Seyfert 1, double-peaked line, radio loud and
radio quiet AGN, to a supermassive binary black hole candidate. Our analysis of
the properties of the broad line region (BLR) of these objects is based on the
variability of the broad emission lines. We hereby give a comparative review of
the variability properties of the broad emission lines and the BLR of seven
different type 1 AGNs, emphasizing some important results, such as the
variability rate, the BLR geometry, and the presence of the intrinsic Baldwin
effect. We are discussing the difference and similarity in the continuum and
emission line variability, focusing on what is the impact of our results to the
supermassive black hole mass determination from the BLR properties.Comment: Published in Frontiers in Astronomy and Space Scienc
Contribution of a Disk Component to Single Peaked Broad Lines of Active Galactic Nuclei
We study the disk emission component hidden in the single-peaked Broad
Emission Lines (BELs) of Active Galactic Nuclei (AGN). We compare the observed
broad lines from a sample of 90 Seyfert 1 spectra taken from the Sloan Digital
Sky Survey with simulated line profiles. We consider a two-component Broad Line
Region (BLR) model where an accretion disk and a surrounding non-disk region
with isotropic cloud velocities generate the simulated BEL profiles. The
analysis is mainly based in measurements of the full widths (at 10%, 20% and
30% of the maximum intensity) and of the asymmetries of the line profiles.
Comparing these parameters for the simulated and observed H broad
lines, we {found} that the hidden disk emission {may} be present in BELs even
if the characteristic {of two peaked line profiles is} absent. For the
available sample of objects (Seyfert 1 galaxies with single-peaked BELs), our
study indicates that, {in the case of the hidden disk emission in single peaked
broad line profiles}, the disk inclination tends to be small (mostly
) and that the contribution of the disk emission to the total flux
should be smaller than the contribution of the surrounding region.Comment: 18 Figures, 1 Table, MNRAS-accepted. MNRAS-accepte
Spectral Optical Monitoring of the Narrow Line Seyfert 1 galaxy Ark 564
We present the results of a long-term (1999--2010) spectral optical
monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a
strong Fe II line emission in the optical. This AGN is a narrow line Seyfert 1
(NLS1) galaxies, a group of AGNs with specific spectral characteristics. We
analyze the light curves of the permitted Ha, Hb, optical Fe II line fluxes,
and the continuum flux in order to search for a time lag between them.
Additionally, in order to estimate the contribution of iron lines from
different multiplets, we fit the Hb and Fe II lines with a sum of Gaussian
components. We found that during the monitoring period the spectral variation
(F_max/F_min) of Ark 564 was between 1.5 for Ha to 1.8 for the Fe II lines. The
correlation between the Fe II and Hb flux variations is of higher significance
than that of Ha and Hb (whose correlation is almost absent). The permitted-line
profiles are Lorentzian-like, and did not change shape during the monitoring
period. We investigated, in detail, the optical Fe II emission and found
different degrees of correlation between the Fe II emission arising from
different spectral multiplets and the continuum flux. The relatively weak and
different degrees of correlations between permitted lines and continuum fluxes
indicate a rather complex source of ionization of the broad line emission
region.Comment: Accepted for publication in ApJ
Constraints on the black hole spin in the quasar SDSS J094533.99+100950.1
The spin of the black hole is an important parameter which may be responsible
for the properties of the inflow and outflow of the material surrounding a
black hole. Broad band IR/optical/UV spectrum of the quasar SDSS
J094533.99+100950.1 is clearly disk-dominated, with the spectrum peaking up in
the observed frequency range. Therefore, disk fitting method usually used for
Galactic black holes can be used in this object to determine the black hole
spin. We develop the numerical code for computing disk properties, including
radius-dependent hardening factor, and we apply the ray-tracing method to
incorporate all general relativity effects in light propagation. We show that
the simple multicolor disk model gives a good fit, without any other component
required, and the disk extends down to the marginally stable orbit. The best
fit accretion rate is 0.13, well below the Eddington limit, and the black hole
spin is moderate, 0.3. The contour error for the fit combined with the
constraints for the black hole mass and the disk inclination gives a constraint
that the spin is lower than 0.8. We discuss the sources of possible systematic
errors in the parameter determinations
The INTEGRAL/IBIS AGN catalogue I: X-ray absorption properties versus optical classification
In this work we present the most comprehensive INTEGRAL AGN sample which
lists 272 objects. Here we mainly use this sample to study the absorption
properties of active galaxies, to probe new AGN classes and to test the AGN
unification scheme. We find that half (48%) of the sample is absorbed while the
fraction of Compton thick AGN is small (~7%). In line with our previous
analysis, we have however shown that when the bias towards heavily absorbed
objects which are lost if weak and at large distance is removed, as it is
possible in the local Universe, the above fractions increase to become 80% and
17%. We also find that absorption is a function of source luminosity, which
implies some evolution in the obscuration properties of AGN. Few peculiar
classes, so far poorly studied in the hard X-ray band, have been detected and
studied for the first time such as 5 XBONG, 5 type 2 QSOs and 11 LINERs. In
terms of optical classification, our sample contains 57% of type 1 and 43% of
type 2 AGN; this subdivision is similar to that found in X-rays if unabsorbed
versus absorbed objects are considered, suggesting that the match between
optical and X-ray classification is overall good. Only a small percentage of
sources (12%) does not fulfill the expectation of the unified theory as we find
22 type 1 AGN which are absorbed and 10 type 2 AGN which are unabsorbed.
Studying in depth these outliers we found that most of the absorbed type 1 AGN
have X-ray spectra characterized by either complex or warm/ionized absorption
more likely due to ionized gas located in an accretion disk wind or in the
biconical structure associated to the central nucleus, therefore unrelated to
the toroidal structure. Among 10 type 2 AGN which resulted to be unabsorbed, at
most 3-4% is still eligible to be classified as a "true" type 2 AGN.Comment: 21 pages, 6 figures, 5 tables. Accepted for publication on MNRAS.
arXiv admin note: text overlap with arXiv:0709.2077 by other author
Broad-line Balmer Decrements in Blue Active Galactic Nuclei
We have investigated the broad-line Balmer decrements (Halpha/Hbeta) for a
large, homogeneous sample of Seyfert 1 galaxies and QSOs using spectroscopic
data obtained in the Sloan Digital Sky Survey. The sample, drawn from the
Fourth Data Release, comprises 446 low redshift (z < 0.35) active galactic
nuclei (AGN) that have blue optical continua as indicated by the spectral
slopes in order to minimize the effect of dust extinction. We find that (i) the
distribution of the intrinsic broad-line Halpha/Hbeta ratio can be well
described by log-Gaussian, with a peak at Halpha/Hbeta=3.06 and a standard
deviation of about 0.03 dex only; (ii) the Balmer decrement does not correlate
with AGN properties such as luminosity, accretion rate, and continuum slope,
etc.; (iii) on average, the Balmer decrements are found to be only slightly
larger in radio-loud sources (3.37) and sources having double-peaked
emission-line profiles (3.27) compared to the rest of the sample. We therefore
suggest that the broad-line Halpha/Hbeta ratio can be used as a good indicator
for dust extinction in the AGN broad-line region; this is especially true for
radio-quiet AGN with regular emission-line profiles, which constitute the vast
majority of the AGN population.Comment: To appear in MNRAS. The data and the fitted parameters for the
decomposed spectral components (continuum, FeII and other emission lines) of
the 446 blue AGNs are available at
http://staff.ustc.edu.cn/~xbdong/Data_Release/blueAGN_DR4
Broad Line Region Physical Conditions along the Quasar Eigenvector 1 Sequence
[Abridged] We compare broad emission line profiles and estimate line ratios
for all major emission lines between Ly-alpha and H-beta in a sample of six
quasars. The sources were chosen with two criteria in mind: the existence of
high quality optical and UV spectra as well as the possibility to sample the
spectroscopic diversity in the 4D Eigenvector 1 context . In the latter sense
each source occupies a region (bin) in the FWHM(H-beta) vs. optical FeII
strength plane that is significantly different from the others. High S/N H-beta
emission line profiles are used as templates for modeling the other lines
(Ly-alpha, CIV 1549, HeII 1640, Al III 1860, Si III] 1892, and Mg II 2800). We
can adequately model all broad lines assuming the existence of three components
distinguished by blueshifted, unshifted and redshifted centroids (indicated as
blue, broad and very broad component respectively). The broad component (high
electron density, low ionization parameter; high column density) is present in
almost all type-1 quasars and therefore corresponds most closely to the
classical broad line emitting region (the reverberating component). The blue
component emission (lower electron density; high ionization; low column
density) arises in less optically thick gas; it is often thought to arise in an
accretion disk wind. The least understood component involves the very broad
component (high ionization and large column density). It is perhaps the most
distinguishing characteristic of quasars with FWHM H-beta > 4000 km/s that
belong to the so-called Population B of our 4DE1 space. Population A quasars
(FWHM H-beta < 4000 km/s) are dominated by broad component emission in H-beta
and blue component emission in CIV 1549 and other high ionization lines. 4DE1
appears to be the most useful current context for revealing and unifying
spectral diversity in type-1 quasars.Comment: 7 Tables, 5 Figures; accepted for publication in Monthly Notices of
the Royal Astronomical Societ
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