14 research outputs found
The sizes of BLRs and BH masses of double-peaked broad low-ionization emission line objects
In this paper, the sizes of the BLRs and BH masses of DouBle-Peaked broad
low-ionization emission line emitters (dbp emitters) are compared using
different methods: virial BH masses vs BH masses from stellar velocity
dispersions, the size of BLRs from the continuum luminosity vs the size of BLRs
from the accretion disk model. First, the virial BH masses of dbp emitters
estimated by the continumm luminosity and line width of broad H are
about six times (a much larger value, if including another dbp emitters, of
which the stellar velocity dispersions are traced by the line widths of narrow
emission lines) larger than the BH masses estimated from the relation which is a more accurate relation to estimate BH masses. Second, the
sizes of the BLRs of dbp emitters estimated by the empirical relation of
are about three times (a much larger value, if
including another dbp emitters, of which the stellar velocity dispersions are
traced by the line widths of narrow emission lines) larger than the mean
flux-weighted sizes of BLRs of dbp emitters estimated by the accretion disk
model. The higher electron density of BLRs of dbp emitters would be the main
reason which leads to smaller size of BLRs than the predicted value from the
continuum luminosity.Comment: 7 pages, two figures and one table. Accepted by MNRA
The size of BLRs of low luminous Active Galactic Nuclei
We study the size of BLRs of low luminosity Active Galactic Nuclei, also
called 'dwarf AGN', defined as having ()). We more than double the sample size analyzed previously (Wang &
Zhang 2003, hereafter Paper I). In this study we first confirm our previous
result that the sizes of BLRs of low luminosity AGN are larger than the ones
expected from the empirical relation valid for
'normal' AGN: Seyfert 1s and quasars, except for the objects with accretion
rate . Second, we find a positive correlation
between the line width of the narrow emission line (as tracer of velocity
dipersion and thus bulge and black hole mass) and the size of BLRs for both
normal and low luminosity AGN. In this paper we find a non-linear dependence of
the BLRs sizes of low luminosity AGN on BH masses. We also show that their
sizes of BLRs are more strongly dominated by the 'specific accretion rate'
defined as , than
by the masses of their cetral black holes. As an expected result, the distance
of emission regions of low-ionization broad H of NGC 4395 should be
consistent with the value from the empirical relation of , according to the high accretion rate.Comment: Accepted by MNRA
An Optical Spectroscopic Atlas of Low-Redshift Active Galactic Nuclei
We present a spectral atlas of the Hβ region for 215 type 1 AGNs (luminous Seyfert 1/radio galaxy nuclei and low-z quasars) up to z ≈ 0.8. Line profiles and measures were derived from the database of intermediate resolution spectra (R 1000) with average continuum level S/N ratio ≈30. Parameters including rest frame equivalent width and FWHM are provided for the Fe IIopt blend at λ4570, Hβ, He II λ4686, and the [O III] λλ4959, 5007 emission lines. We extract clean broad component Hβ profiles and provide wavelength measurements at 0, 1/4, 1/2, 3/4, and 0.9 peak intensity levels in order to permit a quantitative definition of the Hβ broad component for statistical studies. We also discuss sources of uncertainty, selection effects, and biases in our sample. The data are especially important for tests of the eigenvector 1 parameter space occupation and correlation. We show that the I Zw 1 template Fe IIopt spectrum reproduces well the observed Fe IIopt emission for a wide range of line width and strength. A detailed analysis of the data within the eigenvector 1 context is deferred to a companion paper
A 3-Dimensional study of the Local Environment of Bright IRAS Galaxies: The AGN/Starburst connection
We present a 3-dimensional study of the local ( kpc) and the
large scale ( 1 Mpc) environment of Bright IRAS Galaxies
(BIRGs). For this purpose we use 87 BIRGs located at high galactic latitudes
(with 0.0080.018) as well as a control sample of non-active
galaxies having the same morphological, redshift and diameter size
distributions as the corresponding BIRG sample. Using the Center for
Astrophysics (CfA2) and Southern Sky Redshift Survey (SSRS) galaxy catalogues
()as well as our own spectroscopic observations
() for a subsample of the original BIRG sample, we find that
the fraction of BIRGs with a close neighbor is significantly higher than that
of their control sample. Comparing with a related analysis of Sy1 and Sy2
galaxies of Koulouridis et al. (2006) we find that BIRGs have a similar
environment as Sy2s, although the fraction of BIRGs with a bright close
neighbor is even higher than that of Sy2 galaxies. An additional analysis of
the relation between FIR colors and the type of activity of each BIRG shows a
significant difference between the colors of strongly-interacting and
non-interacting starbursts and a resemblance between the colors of
non-interacting starbursts and Sy2s. Our results support the view where close
interactions can drive molecular clouds towards the galactic center, triggering
starburst activity and obscuring the nuclear activity. When the close neighbor
moves away, starburst activity is reduced with the simultaneous appearance of
an obscured (type 2) AGN. Finally, the complete disentanglement of the pair
gives birth to an unobscured (type 1) AGN.Comment: Accepted for publication in The Astrophysical Journal,10 pages, 4
figure
A Multiwavelength Study of Stephan's Quintet
Stephan's Quintet (SQ) is a compact group that we find in an atypical moment
when a high velocity intruder is passing through it. The intrusion is
particularly interesting because a previous intruder had stripped most of the
gas from the group members. This debris field was shocked in the ongoing
collision with the new intruder. This evolutionary history agrees well with
observations and explains how a strongly interacting system can show low levels
of star formation. We present new multiwavelength data including previously
unpublished ROSAT X-ray, Ha interference filter/FP, ISO MIR/FIR and radio line
and continuum images. These observations and previously published data provide
new insights as well as support for some previous hypotheses. 1) FP and HI
velocities allow us to unambiguously distinguish between gas associated with SQ
and the new intruder.
2) Most detected emission regions are found in the remnant ISM of the NI
which allows us to infer its size and present physical state. 3) The few
emission regions associated with the stripped ISM of SQ include the best
candidate tidal dwarf galaxy. 4) Multiwavelength data suggest that strong
MIR/FIR emission from the Seyfert 2 nucleus of NGC7319 comes from dust heated
directly by a power-law continuum rather than a starburst. 5) The
correspondance between extended X-ray/radio continuum/forbidden optical
emission confirms the existence of a large scale shock in SQ.Comment: In press in AJ. 44 pages, 10 Postscript figures, uses aastex.st
Nuclear Activity In Isolated Galaxies
We present a spectroscopic study of the incidence of AGN nuclear activity in
two samples of isolated galaxies (Karachentseva, V.E. & Varela, J.). Our
results show that the incidence of non-thermal nuclear activity is about 43%
and 31% for galaxies with emission lines and for the total sample 40% and 27%
respectively. For the first time we have a large number of bona-fide isolated
galaxies (513 objects), with statistically significant number of all types. We
find a clear relation between bulge mass and the incidence of nuclear activity
in the sample with emission lines. This relation becomes flatter when we take
into account the complete sample with no emission line galaxies. A large
fraction (~70%) of elliptical galaxies or early type spirals have an active
galactic nucleus and ~70% of them are LINERs. Only 3% of the AGN show the
presence of broad lines (a not a single one can be classified as type 1 AGN).
This is a remarkable result which is completely at odds with the unified model
even if we consider warped or clumpy tori. Finally, we interpret the large
fraction of AGN in isolated galaxies as the result of secular evolution of
their supermasive black holes.Comment: 7 figures, 7 table
Spectrophotometrie des noyaux actifs des galaxies
SIGLECNRS T 59645 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc