Active | An electronic publication dedicated to |
Galaxies | the observation and theory of |
Newsletter | active galaxies |
No. 98 -- May 2005 | Editor: Rob Beswick (rb@ast.man.ac.uk) |
The Active Galaxies Newsletter is produced monthly. The deadline for
contributions is the last friday of the month. The Latex macros for
submitting abstracts and dissertation abstracts are appended to each
issue of the newsletter and are also available on the web page.
Rob Beswick
X-ray Lighthouses of the High-Redshift Universe. II. Further Snapshot
Observations of the Most Luminous
Quasars with Chandra
C. Vignali, W. N. Brandt
, D. P. Schneider
and S. Kaspi
Dipartimento di Astronomia, Università degli Studi di
Bologna, Via Ranzani 1, 40127 Bologna, Italy
INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1,
40127 Bologna, Italy
Department of Astronomy and Astrophysics, The Pennsylvania State
University, 525 Davey Laboratory, University Park, PA 16802, USA
School of Physics and Astronomy, Raymond and Beverly Sackler
Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
Physics Department, Technion, Haifa, 32000, Israel
We report on Chandra observations of a sample of 11 optically luminous
(
) quasars at
=3.96-4.55 selected from the Palomar Digital
Sky Survey and the Automatic Plate Measuring Facility Survey. These are among
the most luminous
quasars known and hence represent ideal witnesses
of the end of the ``dark age ''. with
2-57 counts in the observed 0.5-8 keV band. These detections
increase the number of X-ray detected AGN at
to
90;
overall, Chandra has detected
85% of the high-redshift quasars
observed with snapshot (few kilosecond) observations. the two X-ray undetected quasars, displays a number of notable features in its
rest-frame ultraviolet spectrum, the most prominent being broad, deep Si IV and C IV absorption lines. spectral index for the present sample (
=
1.88
) is steeper than that typically found for
quasars but consistent with the expected value from the known
dependence of this spectral index on quasar luminosity.
We present joint X-ray spectral fitting for a sample of 48 radio-quiet quasars
in the redshift range 3.99-6.28 for which Chandra observations are
available. The X-ray spectrum ( 870 counts) is well parameterized by a
power law with
=1.93
in the rest-frame
2-40 keV band, and a tight upper limit of
5
cm
is obtained on any average intrinsic X-ray
absorption. There is no indication of any significant evolution in the X-ray
properties of quasars between redshifts zero and six, suggesting that the
physical processes of accretion onto massive black holes have not changed over
the bulk of cosmic time.
Accepted by Astron. J.
E-mail contact: cristian.vignali@bo.astro.it,
preprint available at
http://www.astro.psu.edu/niel/papers/papers.html and as
astro-ph/0503301.
Discovery of 10 m silicate emission in quasars.
Evidence of the AGN unification scheme.
R. Siebenmorgen, M. Haas
, E. Krügel
, and B. Schulz
European Southern Observatory, Karl-Schwarzschildstr. 2,
D-85748 Garching b. München.
Astronomisches Institut, Ruhr-Universität,
Universitätsstr. 150, D-44780 Bochum.
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69,
Postfach 2024, D-53010 Bonn.
IPAC, California Institute of Technology (Caltech), Pasadena,
CA 91125, USA.
According to the unified scheme, AGN are surrounded by a dust-torus and the
observed diversity of AGN properties results from the different orientations
relative to our line of sight. The strong resonance of silicate dust at 10
m is therefore, as expected, seen in absorption towards many type-2 AGN.
In type-1 AGN, it should be seen in emission because the hot inner surface of
the dust torus becomes visible, however, this has not been observed so far, thus
challenging the unification scheme or leading to exotic modifications of the
dust-torus model. Here we report the discovery of the 10
m silicate
feature in emission in two luminous quasars with the Infrared Spectrograph of
the Spitzer Space Telescope.
Accepted by A&A Letters
E-mail contact: rsiebenm@eso.org
Preprint available at: astroph/0504233 or
http://www.eso.org/~rsiebenm/FTP/SiQuasars.pdf
The XMM-Newton view of Mrk 3 and IXO 30
Stefano Bianchi
, Giovanni Miniutti
, Andrew C.
Fabian
, Kazushi Iwasawa
XMM-Newton Science Operations Center, European Space Astronomy
Center, ESA, Apartado 50727, E-28080 Madrid, Spain
Dipartimento di Fisica, Università degli Studi Roma Tre, Via
della Vasca Navale 84, I-00146, Roma, Italy
Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA
We present the analysis of the XMM-Newton EPIC pn spectrum of the
Seyfert 2 galaxy, Mrk 3. We confirm that the source is dominated by a pure
Compton reflection component and an iron K line, both produced as
reflection from a Compton-thick torus, likely responsible also for the large
column density (
cm
) which is pierced
by the primary powerlaw only at high energies. A low inclination angle and an
iron underabundance of a factor
, suggested by the amount of
reflection and the depth of the iron edge, are consistent with the iron
K
line EW with respect to the Compton reflection component, being
eV. Moreover, the iron line width,
eV, if interpreted in terms of Doppler broadening due to the Keplerian rotation
of the torus, puts an estimate to the inner radius of the latter,
pc. Finally, two different photoionised
reflectors are needed to take into account a large number of soft X-ray emission
lines from N, O, Ne, Mg, Si, Fe L and the FeXXV emission line at
keV. RGS spectra show that the soft X-ray spectrum is
dominated by emission lines, while the underlying continuum is best fitted by an
unabsorbed powerlaw with the same photon index of the primary continuum,
produced as reflection by a photoionised material with a column density of a few
cm
. We also present the first X-ray spectrum of ROSAT
source IXO 30, which shows a huge iron line at
keV and is
well represented either by an absorbed powerlaw with
or
bremsstrahlung emission at a temperature of
keV. Its
spectral properties point to a likely identification in terms of a weak Galactic
Cataclysmic Variable, but the lack of any optical counterpart precludes
excluding other possibilities, like an ULX at the distance of Mrk 3.
Accepted by MNRAS
E-mail contact: Stefano.Bianchi@sciops.esa.int,
preprint available at
http://es.arxiv.org/abs/astro-ph/0503623
HST/STIS low dispersion spectroscopy of three Compact Steep Spectrum sources. Evidence for jet-cloud interaction
A. Labiano, C.P. O'Dea
, R.Gelderman
, W.H. de Vries
,
D.J. Axon
, P.D. Barthel
, S.A. Baum
, A. Capetti
, A.M.
Koekemoer
, R. Morganti
and C.N. Tadhunter
Kapteyn Astronomical Institute, Groningen, 9700 AV, The Netherlands
Space Telescope Science Institute, Baltimore, MD 21218, USA
Department of Physics, Rochester Institute of Technology, Rochester,
NY, 14623, USA
Western Kentucky University, Bowling Green KY 42101, USA
Lawrence Livermore National Lab., Livermore CA, 94550, USA
Department of Physics, Rochester Institute of Technology, Rochester
NY,14623, USA
Center for Imaging Science, Rochester Institute of Technology, Rochester,
NY, 14623, USA
Osservatorio Astronomico di Torino, Pino Torinesse (TO), 10025, Italy
Istituto di Radioastronomia del CNR, Bologna, 40129, Italy
Netherlands Foundation for Astronomy, Dwingeloo, 7990 AA, The
Netherlands
University of Sheffield, Western Bank, Sheffield, S10 2TN,UK
We present Hubble Space Telescope Imaging Spectrograph long-slit spectroscopy of the emission line nebulae in the compact steep spectrum radio sources 3C 67, 3C 277.1, and 3C 303.1. We derive BPT (Baldwin- Philips-Terlevich; Baldwin et al. 1981) diagnos tic emission line ratios for the nebulae which are consistent with a mix of shock excitation and photoionization in the extended gas. In addition, line ratios indicative of lower ionization gas are found to be associated with higher gas velocities. The r esults are consistent with a picture in which these galaxy scale radio sources interact with dense clouds in the interstellar medium of the host galaxies, shocking the clouds thereby ionizing and accelerating them.
Accepted by Astronomy & Astrophysics
E-mail contact: labiano@astro.rug.nl,
Preprint available at
http://arXiv.org/abs/astro-ph/0504330
ISO observations and models of galaxies with Hidden Broad Line Regions
A. Efstathiou and R. Siebenmorgen
School of Computer Science and Engineering, Cyprus College,
6 Diogenes Street, Engomi, 1516 Nicosia, Cyprus.
European Southern Observatory, Karl-Schwarzschildstr. 2,
D-85748 Garching b. München.
In this paper we present ISO mid-infrared spectrophotometry
and far-infrared photometry of galaxies with Hidden
Broad Line Regions (HBLR). We also present radiative transfer models
of their spectral energy distributions which enable us to separate
the contributions from the dusty disc of the AGN and the dusty
starbursts. We find that the combination of tapered discs
(discs whose thickness increases with distance from the central source
in the inner part but stays constant in the outer part) and starbursts
provide good fits to the data. The tapered discs dominate in the
mid-infrared part of the spectrum and the starbursts in the far-infrared.
After correcting the AGN luminosity for anisotropic emission we find that
the ratio of the AGN luminosity to the starburst luminosity,
, ranges from about unity for IRAS14454-4343 to about
13 for IRAS01475-0740. Our results suggest that the warm IRAS colours
of HBLR are due to the relatively high
. Our fits are
consistent with the unified model and the idea that the infrared emission
of AGN is dominated by a dusty disc in the mid-infrared and starbursts
in the far-infrared.
Accepted by A&A
E-mail contact: efstathi@cycollege.ac.cy
Preprint available at:
astroph/0504432 or http://www.eso.org/~rsiebenm/FTP/0504432.pdf
Discovery of Optical Emission in the Hotspots of Three 3CR Quasars: High-Energy Particle Acceleration in Powerful Radio Hotspots
C.C. Cheung, J.F.C. Wardle
and Tingdong Chen
Jansky Postdoctoral Fellow; National Radio Astronomy Observatory and MIT,
Kavli Institute for Astrophysics & Space Research, 77 Massachusetts
Ave., Cambridge, MA 02139
Department of Physics, MS 057, Brandeis University,
Waltham, MA 02454
Archival Hubble Space Telescope WFPC2 images were used to search for optical
emission associated with the radio jets of a number of luminous quasars. From
this search, we report new optical hotspot detections in the well-known blazar
3C 454.3 and the lobe-dominated quasars 3C 275.1 and 3C 336. We also find
optical emission in the vicinity of the hotspot in 3C 208, but believe this is a
chance alignment. Optical emission from the arcsecond-scale jet in 3C 454.3 is
also detected. Multi-frequency archival radio data from the VLA and MERLIN are
analyzed, and the synchrotron spectra of these high-power hotspots are
presented. We estimate that their break frequencies are in the range of
Hz, with large uncertainties due to the wide gap in frequency
coverage between the radio and optical bands. We also calculate their
equipartition magnetic fields, and find that the anti-correlation between break
frequency and magnetic field found by Brunetti et al. for lower power hotspots
extends to these high power hotspots. This supports their model of hot-spots
based on shock acceleration and synchrotron losses.
Accepted by Astrophys. J.
E-mail contact: ccheung@space.mit.edu,preprint available at http://arxiv.org/abs/astro-ph/0503634
Soft X-ray and Ultraviolet Emission Relations in Optically Selected AGN Samples
I. V. Strateva, W. N. Brandt
, D. P. Schneider
, D. G. Vanden
Berk
and C. Vignali
Department of Astronomy and Astrophysics, 525 Davey Lab,
Pennsylvania State University, University Park, PA 16802
Dipartimento di Astronomia, Università degli Studi di Bologna,
Via Ranzani 1, 40127 Bologna, Italy
INAF - Osservatorio Astronomico di Bologna, Via Ranzani 1,
40127 Bologna, Italy
Using a sample of 228 optically selected Active Galactic Nuclei (AGNs) in the
0.01-6.3 redshift range with a high fraction of X-ray detections
(81-86%), we study the relation between rest-frame UV and soft X-ray emission
and its evolution with cosmic time. The majority of the AGNs in our sample (155
objects) have been selected from the Sloan Digital Sky Survey (SDSS) in an
unbiased way, rendering the sample results representative of all SDSS AGNs. The
addition of two heterogeneous samples of 36 high-redshift and 37 low-redshift
AGNs further supports and extends our conclusions. We confirm that the X-ray
emission from AGNs is correlated with their UV emission, and that the ratio of
the monochromatic luminosity emitted at 2keV compared to 2500Å decreases
with increasing luminosity (
, where
is in
units), but does not change with cosmic time. These
results apply to intrinsic AGN emission, as we correct or control for the
effects of the host galaxy, UV/X-ray absorption, and any X-ray emission
associated with radio emission in AGNs. We investigate a variety of systematic
errors and can thereby state with confidence that (1) the
-
anti-correlation is real and not a result of
accumulated systematic errors and (2) any
dependence on redshift
is negligible in comparison. We provide the best quantification of the
-
relation to date for normal radio-quiet AGNs; this
should be of utility for researchers pursuing a variety of studies.
Accepted by Astron. J.
E-mail contact: iskra@astro.psu.edu,
preprint available at
http://arxiv.org/abs/astro-ph/0503009
XMM-Newton Spectroscopy of the Starburst Dominated Ultra Luminous Infrared Galaxy NGC6240
Hagai Netzer, Doron Lemze
Shai Kaspi
, I.M. George
, T.J.
Turner
, D. Lutz
, T. Boller
, Doron Chelouche
School of Physics and Astronomy and the Wise
Observatory, Tel-Aviv University, Tel-Aviv 69978,
Israel
Physics Department, The Technion, Haifa 3200, Israel
Physics Department, University of Maryland Baltimore County,
Baltimore MD 21250, USA
Max-Planck-Institut für extraterrestrische Physik, Postfach 1312,
85741 Garching, Germany
School of Natural Sciences, Institute for Advanced Study, Einstein
Dr. Princeton, NJ 08540, USA
We present new XMM-Newton observation of the Ultra Luminous Infrared Galaxy
(ULIRG) NGC6240. We analyze the reflecting grating spectrometer (RGS) data,
and data from the other instruments, and find a starburst dominated 0.5-3 keV
spectrum with global properties resembling those observed in M82 but with a much
higher luminosity. We show that the starburst region can be divided into an
outer zone, beyond a radius of about 2.1 kpc, with a gas temperature of about
K and a central region with temperatures in the range 2-6
K. The gas in the outer region emits most of the observed OVIII
line and the gas in the inner region the emission lines of higher
ionization ions, including a strong FeXXV line. We also identify a small
inner part, very close to the active nuclei, with typical Seyfert 2 properties
including a large amount of photoionized gas producing a strong Fe K
6.4 keV line. The combined abundance, temperature and emission measure analysis
indicates super solar Ne/O, Mg/O, Si/O, S/O and possibly also Fe/O. The analysis
suggests densities in the range of 0.07-0.28
cm
and a
total thermal gas mass of
solar masses,
where
is the volume filling factor. We used a simple model to argue
that a massive starburst with an age of
years can explain
most of the observed properties of the source. NGC6240 is perhaps the clearest
case of an X-ray bright luminous AGN, in a merger, whose soft X-ray spectrum is
dominated by a powerful starburst.
Accepted by ApJ
E-mail contact: netzer@wise.tau.ac.il
Type 2 counterparts of narrow-line Seyfert 1 galaxies
G. C. Dewangan & R. E. Griffiths
Departmnt of Physics, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213 US
Unified models of Seyfert galaxies, based on viewing angles,
successfully explain the observed differences between type 1 and 2
Seyferts. The existence of a range in accretion rates (
) relative to the Eddington rate (from broad-line Seyfert 1s
to narrow-line Seyfert 1s or NLS1s) and the unification of Seyfert
galaxies imply that there must be type 2 counterparts of NLS1s i.e.,
Seyfert 2s with high accretion rate or small black
hole mass. One such Seyfert 2, NGC 5506, has already been unmasked
based on near infra-red spectroscopy. Here we confirm the above
result, and present evidence for two additional type 2 counterparts
of NLS1s based on XMM-Newton observations. The three AGNs NGC 7314,
NGC 7582 and NGC 5506, with a type 1.9/2 optical spectrum, show
extremely rapid variability by factors
,
, and
in
,
and
, respectively, and steep
spectrum (
) in their intrinsic X-ray
emission, characteristic of NLS1 galaxies. These observations
establish the `obscured NLS1 galaxies' as a subclass of
Seyfert 2 galaxies.
Accepted by ApJ Letters
E-mail contact: gulabd@cmu.edu,
preprint available at
http://xxx.lanl.gov/abs/astro-ph/0504279
The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei
Shai Kaspi, Dan Maoz
, Hagai Netzer
, Bradley M.
Peterson
, Marianne Vestergaard
and Buell T. Jannuzi
School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv
69978, Israel
Physics Department, Technion, Haifa 32000, Israel
Department of Astronomy, The Ohio State University, 140 West 18th
Avenue, Columbus, OH 43210
Steward Observatory, The University of Arizona, 933 North Cherry
Avenue, Tucson, AZ 85721
National Optical Astronomy Observatory, P.O. Box
26732, Tucson, AZ 85719
We reinvestigate the relationship between the characteristic broad-line region
size () and the Balmer emission-line, X-ray, UV, and optical
continuum luminosities. Our study makes use of the best available
determinations of
for a large number of active galactic nuclei
(AGNs) from Peterson et al. Using their determinations of
for a
large sample of AGNs and two different regression methods, we investigate the
robustness of our correlation results as a function of data sub-sample and
regression technique. Though small systematic differences were found depending
on the method of analysis, our results are generally consistent. Assuming a
power-law relation
, we find the mean
best-fitting
is about
for the optical continuum and the
broad H
luminosity, about
for the UV continuum luminosity,
and about
for the X-ray luminosity. We also find an intrinsic
scatter of
% in these relations. The disagreement of our results with
the theoretical expected slope of 0.5 indicates that the simple assumption of
all AGNs having on average same ionization parameter, BLR density, column
density, and ionizing spectral energy distribution, is not valid and there is
likely some evolution of a few of these characteristics along the luminosity
scale.
Accepted by The Astrophysical Journal
E-mail contact: shai@wise.tau.ac.il,
preprint available at
http://arxiv.org/abs/astro-ph/0504484
Optical Monitoring of PKS 1510089: A Binary Black Hole System?
J. Wu, X. Zhou
, B. Peng
, J. Ma
, Z. Jiang
, and J.
Chen
National Astronomical Observatories, Chinese Academy of
Sciences, 20A Datun Road, Beijing 100012, China
Three deep flux minima were observed with nearly the same time-scales and
intervals for the blazar PKS 1510089 in the past few years. A binary black
hole system was proposed to be at the nucleus of this object, and a new minimum
was predicted to occur in 2002 March. We monitored this source with a 60/90 cm
Schmidt telescope from 2002 February to April. In combination with the data
obtained by Xie et al. (2004) in the same period, we presented for the 2002
minimum a nearly symmetric light curve, which would be required by an eclipsing
model of a binary black hole system. We also constrained the time-scale of the
minimum to be 35 min, which is more consistent with the time-scales (
min) of the three previous minima than the 89 min time-scale given by the same
authors. The wiggling miniarcsecond radio jet observed in this object is taken
as a further evidence for the binary black hole system. The `coupling' of the
periodicity in light curve and the helicity in radio jet is discussed in the
framework of a binary black hole system.
Accepted by MNRAS
E-mail contact: jhwu@bao.ac.cn
preprint available at
http://arxiv.org/abs/astro-ph/0504587
The detection of silicate emission from quasars at 10 and 18 microns
Lei Hao, H. W. W. Spoon
, G. C. Sloan
, J. A. Marshall
, L.
Armus
, A. G. G. M. Tielens
, B. Sargent
, I. M. van Bemmel
, V.
Charmandaris
, D. W. Weedman
, and J. R. Houck
Cornell University, Astronomy Department, Ithaca, NY 14853-6801
Caltech, Spitzer Science Center, MS 220-6, Pasadena, CA 91125
SRON National Institute for Space Research and
Kapteyn Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands
University of Rochester, Department of Physics and
Astronomy, Rochester, NY 14627
Space Telescope Science Institute, 3700 San Martin Drive,
Baltimore, MD 21218
University of Crete, Department of Physics, P. O. Box 2208,
GR-71003, Heraklion, Greece
Chercheur Associé Obs. de Paris, 61 Ave. de
l'Observatoire, F-75014 Paris, France
We report the spectroscopic detection of silicate emission at 10 and 18mm in five PG quasars, the first detection of these two features in galaxies
outside the Local Group. This finding is consistent with the unification model
for Active Galactic Nuclei (AGNs), which predicts that an AGN torus seen pole-on
should show a silicate emission feature in the mid-infrared. The strengths of
the detected silicate emission features range from 0.12 to 1.25 times the
continuum at 10m
m and from 0.20 to 0.79 times the continuum at 18m
m.
The silicate grain temperatures inferred from the ratio of 18-to-10
m
silicate features under the assumption of optically thin emission range from 140
to 220K.
Accepted by Astrophysical. J. Letter
E-mail contact: haol@isc.astro.cornell.edu,
preprint available
at http://arxiv.org/abs/astro-ph/0504423
[O II] Emission in Quasar Host Galaxies: Evidence for a Suppressed Star Formation Efficiency
Luis C. Ho
The Observatories of the Carnegie Institution of Washington, 813 Santa
Barbara St., Pasadena, CA 91101
The [O II] 3727 line, a commonly used estimator of star formation rate
in extragalactic surveys, should be an equally effective tracer of star
formation in the host galaxies of quasars, whose narrow-line regions are
expected to produce weak low-ionization emission. Quasar spectra generally show
little or no [O II] emission beyond that expected from the active nucleus
itself. The inferred star formation rates in optically selected quasars are
typically below a few
yr
, and some significantly less. Quasars
do not appear to occur coevally with starbursts. Recent observations, on the
other hand, reveal abundant molecular gas in low-redshift quasars. These two
results suggest that the star formation efficiency in quasar host galaxies is
somehow suppressed during the active phase of the nucleus. The low star
formation rates also imply that the nonstellar nucleus powers the bulk of the
thermal infrared emission in radio-quiet quasars.
Accepted by ApJ.
E-mail contact: lho@ociw.edu,
preprint available at
http://xxx.lanl.gov/abs/astro-ph/0504642
``Low-state'' Black Hole Accretion in Nearby Galaxies
Luis C. Ho
The Observatories of the Carnegie Institution of Washington, 813 Santa
Barbara St., Pasadena, CA 91101
I summarize the main observational properties of low-luminosity AGNs in nearby galaxies to argue that they are the high-mass analogs of black hole X-ray binaries in the ``low/hard'' state. The principal characteristics of low-state AGNs can be accommodated with a scenario in which the central engine is comprised of three components: an optically thick, geometrically accretion disk with a truncated inner radius, a radiatively inefficient flow, and a compact jet.
To appear in From X-ray Binaries to Quasars: Black Hole Accretion on All Mass Scales, ed. T. J. Maccarone, R. P. Fender, and L. C. Ho (Dordrecht: Kluwer).
E-mail contact: lho@ociw.edu,
preprint available at
http://xxx.lanl.gov/abs/astro-ph/0504643
A Comparison of Stellar and Gaseous Kinematics in the Nuclei of Active Galaxies
Jenny E. Greene and Luis C. Ho
Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,
Cambridge, MA 02138
The Observatories of the Carnegie Institution of Washington, 813 Santa
Barbara St., Pasadena, CA 91101
To investigate the relationship between black holes and their host galaxies,
many groups have used the width of the [OIII] line as a
substitute for the stellar velocity dispersion (
) of galaxy bulges.
We directly test this assumption with a large and homogeneous sample of
narrow-line active galactic nuclei from the Sloan Digital Sky Survey. We
consider multiple transitions ([OII]
, [OIII]
, and
[SII]
) and various techniques for quantifying the
line width in order to obtain a calibration between the gas velocity dispersion,
, and
. We find that
of the low-ionization lines
traces
, as does
for the core [OIII] after its asymmetric
blue wing is properly removed, although in all cases the correlation between
and
has considerable scatter. While the gas kinematics
of the narrow-line region of active galaxies are primarily governed by the
gravitational potential of the stars, the accretion rate, as traced by the
Eddington luminosity ratio, seems to play an important secondary role.
Departures from virial motions correlate systematically with accretion rate. We
discuss the implications of these results for previous studies that use [OIII] line widths to infer stellar velocity dispersions in quasars and narrow-line
Seyfert 1 galaxies.
Accepted by ApJ.
E-mail contact: jgreene@cfa.harvard.edu,
preprint available at
http://xxx.lanl.gov/abs/astro-ph/0503675
Long-term variability of the optical emission lines in the nuclear spectrum of the Seyfert galaxy NGC 3227
I.Pronik, L.Metik
Crimean Astrophysical Observatory, Nauchny, Crimea, Ukraine;
Isaac Newton Institute of Chile, Crimean Branch, Ukraine
53 spectrograms in the optical region (3700-7300 Å) with the spectral
resolution 8Åhave been obtained for the Seyfert nucleus of the galaxy
NGC 3227 with the 6-m telescope on 1977 January while the nucleus was in the
historically important epoch of its extreme maximum brightness. Width of the
slit was 1
, length of the box during the spectra measurements was 1.5
.
Data obtained by us and those compiled from literature showed that profiles of
the Balmer lines H
, H
and H
are different evidencing that
the gas emitting these lines is highly self-absorbed. It was shown that narrow
components of the profiles revealed by Rubin and Ford kept their positions
(radial velocities) over 25 years. The components showed intensity variations
compare to the central one from minimum to maximum of the nucleus brightness.
The same variations were observed by us earlier in the emission line profiles of
the NGC 7469 nucleus spectrum. Narrow profile components can reflect long-lived
flows or jets in the broad line region (BLR). Obtained facts evidenced that
long-lived gas streams and flows causing narrow components of broad line
profiles presented not only when BLR of accretion disc is strong but when BLR of
accretion disc declined. Blue bump at radial velocity of -5000 km/s in H
profile was revealed in spectra of high states of the nucleus, which disappeared
in low state. One of the interpretations of this event can be in the framework
of a model of one-sided or two-sided gas ejection during the high state of the
nucleus, positive radial velocities of which being screened out by a
circumnuclear disk.
Accepted by Astrphysics and Space Science
E-mail contact: ipronik@crao.crimea.ua