91 research outputs found
Jet directions in Seyfert galaxies: B and I imaging data
We present the results of broad-band B and I imaging observations for a
sample of 88 Seyfert galaxies (29 Seyfert 1's and 59 Seyfert 2's), selected
from a mostly isotropic property, the flux at 60m. We also present the B
and I imaging results for an additional sample of 20 Seyfert galaxies (7
Seyfert 1's and 13 Seyfert 2's), selected from the literature and known to have
extended radio emission. The I band images are fitted with ellipses to
determine the position angle and ellipticity of the host galaxy major axis.
This information will be used in a future paper, combined with information from
radio observations, to study the orientation of radio jets relative to the
plane of their host galaxies (Kinney et al. 2000). Here we present surface
brightness profiles and magnitudes in the B and I bands, as well as mean
ellipticities and major axis position angles.Comment: To appear in The Astrophysical Journal Supplement Series, June 2000.
48 pages, 7 tables, 19 gif and 11 postscript figures. Better quality figures
can be obtained with the autho
An Atlas of Warm AGN and Starbursts from the IRAS Deep Fields
We present 180 AGN candidates based on color selection from the IRAS
slow-scan deep observations, with color criteria broadened from the initial
Point-Source Catalog samples to include similar objects with redshifts up to
z=1 and allowing for two-band detections. Spectroscopic identifications have
been obtained for 80 (44%); some additional ones are secure based on radio
detections or optical morphology, although yet unobserved spectroscopically.
These spectroscopic identifications include 13 Sy 1 galaxies, 17 Sy 2 Seyferts,
29 starbursts, 7 LINER systems, and 13 emission-line galaxies so heavily
reddened as to remain of ambiguous classification. The optical magnitudes range
from R=12.0-20.5; counts suggest that incompleteness is important fainter than
R=15.5. Redshifts extend to z=0.51, with a significant part of the sample at
z>0.2. The sample includes slightly more AGN than star-forming systems among
those where the spectra contain enough diagnostic feature to make the
distinction. The active nuclei include several broad-line objects with strong
Fe II emission, and composite objects with the absorption-line signatures of
fading starbursts. These AGN with warm far-IR colors have little overlap with
the "red AGN" identified with 2MASS; only a single Sy 1 was detected by 2MASS
with J-K > 2. Some reliable IRAS detections have either very faint optical
counterparts or only absorption-line galaxies, potentially being deeply
obscured AGN. The IRAS detections include a newly identified symbiotic star,
and several possible examples of the "Vega phenomenon", including dwarfs as
cool as type K. Appendices detail these candidate stars, and the
optical-identification content of a particularly deep set of high-latitude IRAS
scans (probing the limits of optical identification from IRAS data alone).Comment: ApJ Suppl, in press. Figures converted to JPEG/GIF for better
compression; PDF with full-resolution figures available before publication at
http://www.astr.ua.edu/keel/aoagn.pd
A Hubble Space Telescope Survey of Extended [OIII]5007A Emission in a Far-Infrared Selected Sample of Seyfert Galaxies: Results
We present the results of a Hubble Space Telescope (HST) survey of extended
[OIII] emission in a sample of 60 nearby Seyfert galaxies (22 Seyfert 1's and
38 Seyfert 2's), selected by mostly isotropic properties. The comparison
between the semi major axis size of their [OIII] emitting regions (R_Maj) shows
that Seyfert 1's and Seyfert 2's have similar distributions, which seems to
contradict Unified Model predictions. We discuss possible ways to explain this
result, which could be due either to observational limitations or the models
used for the comparison with our data. We show that Seyfert 1 Narrow Line
Regions (NLR's) are more circular and concentrated than Seyfert 2's, which can
be attributed to foreshortening in the former. We find a good correlation
between the NLR size and luminosity, following the relation R_Maj propto
L([OIII])^0.33, which is flatter than a previous one found for QSO's and
Seyfert 2's. We discuss possible reasons for the different results, and their
implications to photoionization models. We confirm previous results which show
that the [OIII] and radio emission are well aligned, and also find no
correlation between the orientation of the extended [OIII] emission and the
host galaxy major axis. This agrees with results showing that the torus axis
and radio jet are not aligned with the host galaxy rotation axis, indicating
that the orientation of the gas in the torus, and not the spin of the black
hole, determine the orientation of the accretion disk, and consequently the
orientation of the radio jet.Comment: 17 pages including 12 figures, to appear in Ap
Multicolour Optical Imaging of IR-Warm Seyfert Galaxies. V. Morphologies and Interactions. Challenging the Orientation Model
This paper is the last in a series, investigating the optical properties of a
sample of mid-IR Warm Seyfert galaxies and of a control sample of mid-IR cold
galaxies. In the present paper we parametrize the morphologies and interaction
properties of the host galaxies and combine these with the major conclusions in
our previous papers. Our results confirm that nuclear activity is linked to
galactic interactions. We suggest an alternative view for the simple
orientation-obscuration model postulated for Seyfert types 1 and 2, that takes
into account the time evolution of their environmental and morphological
properties. Within this view, an evolutionary link between starburst-dominated
and AGN-dominated IR emission is also suggested, to account for the
observational discriminator (mid-IR excess) between our Warm and Cold samples.Comment: 24 pages, including 6 figures and 3 tables (figure 5 included as
independent file), Submitted to Ap
The Unified Model of Active Galactic Nuclei: II. Evolutionary Connection
(Abbreviated) We assemble a sample composed of 243 nearby Seyfert galaxies
with redshifts to test the unification scheme. The sample contains
94 BLS1s, 44 NLS1s, 36 X-ray absorbed HBLR S2s, 42 X-ray absorbed non-HBLR S2s
and 27 X-ray unabsorbed Seyfert 2s (unabsorbed non-HBLR S2s and HBLR S2s). We
find that: 1) NLS1s have less massive black hole masses than BLS1s; 2) HBLRS2s
have the same mass distribution of the black holes with BLS1s; 3) the absorbed
non-HBLR S2s have less massive black holes than HBLR S2s; 4) unabsorbed
non-HBLR S2s have the most massive black holes. We thus have a queue of black
hole masses from small to large: narrow to broad line Seyfert galaxies,
providing new evidence for the evolutionary sequence of Seyfert galaxies. We
find that the opening angles of the torus in NLS1s and absorbed non-HBLR S2s
are significantly smaller than that in BLS1s and HBLR S2s. The growth of the
black holes and increases of the opening angles of the tori determine the
various appearances of Seyfert galaxies. We also find that the unabsorbed
Seyfert 2 galaxies could be caused by low gas-to-dust ratios in the present
sample. This indicates that the star formation histories could be different in
the unabsorbed from in absorbed Seyfert 2 galaxies, showing evidence for
suppressed star formation by black hole activities. We outline a new
unification scheme based on the orientation hypothesis: Seyfert galaxies can be
unified by including growth of black holes, Eddington ratios, changing opening
angles of tori and gas-to-dust ratios in the tori. Seyfert galaxies are tending
to finally evolve to unabsorbed non-HBLR Seyfert 2 galaxies, in which the black
holes are accreting with low accretion rates and both the broad line region and
dusty torus disappear.Comment: ApJ, vol 661 (2007), in pres
Multicolour Optical Imaging of IR-Warm Seyfert Galaxies. I. Introduction and Sample Selection
The standard AGN unification models attempt to explain the diversity of
observed AGN types by a few fundamental parameters, where orientation effects
play a paramount role. Whether other factors, such as the evolutionary stage
and the host galaxy properties are equally important parameters for the AGN
diversity, is a key issue that we are addressing with the present data. Our
sample of IR-selected Seyfert galaxies is based on the important discovery that
their integrated IR spectrum contains an AGN signature. This being an almost
isotropic property, our sample is much less affected by orientation/obscuration
effects compared to most Seyfert samples. It therefore provides a test-bed for
the orientation-dependent models of Seyferts, involving dusty tori. We have
obtained multi-colour broad and narrow band imaging for a sample of mid-IR
``warm'' Seyferts and for a control sample of mid-IR ``cold'' galaxies. In the
present paper we describe the sample selection and briefly discuss their IR
properties. We then give an overview of the data collected and present
broad-band images for all our objects. Finally, we summarize the main issues
that will be addressed with these data in a series of forthcoming papers.Comment: 18 pages including 3 figures and 5 tables (tables 1,4,5 are included
as independent files
A new twist to an old story: HE 0450-2958, and the ULIRG(optically bright QSO) transition hypothesis
We report on interferometric imaging of the CO J=1--0 and J=3--2 line
emission from the controversial QSO/galaxy pair HE 0450--2958. {\it The
detected CO J=1--0 line emission is found associated with the disturbed
companion galaxy not the luminous QSO,} and implies , which is \ga 30% of the dynamical mass in
its CO-luminous region. Fueled by this large gas reservoir this galaxy is the
site of an intense starburst with , placing
it firmly on the upper gas-rich/star-forming end of Ultra Luminous Infrared
Galaxies (ULIRGs, ). This makes HE 0450--2958 the
first case of extreme starburst and powerful QSO activity, intimately linked
(triggered by a strong interaction) but not coincident. The lack of CO emission
towards the QSO itself renews the controversy regarding its host galaxy by
making a gas-rich spiral (the typical host of Narrow Line Seyfert~1 AGNs) less
likely. Finally, given that HE 0450--2958 and similar IR-warm QSOs are
considered typical ULIRG(optically bright QSO) transition candidates, our
results raise the possibility that some may simply be {\it gas-rich/gas-poor
(e.g. spiral/elliptical) galaxy interactions} which ``activate'' an optically
bright unobscured QSO in the gas-poor galaxy, and a starburst in the gas-rich
one. We argue that such interactions may have gone largely unnoticed even in
the local Universe because the combination of tools necessary to disentagle the
progenitors (high resolution and S/N optical {\it and} CO imaging) became
available only recently.Comment: 25 pages, 5 figures, accepted for publication by The Astrophysical
Journa
Molecular Gas in the Powerful Radio Nucleus of the Ultraluminous Infrared Galaxy PKS 1345+12
Millimeter CO(1-0) interferometry and high resolution, Hubble Space Telescope
(HST) 1.1, 1.6, and 2.2 micron imaging of the radio compact galaxy PKS 1345+12
are presented. With an infrared luminosity of 2x10^{12} L_sun, PKS 1345+12 is a
prime candidate for studying the link between the ultraluminous infrared galaxy
phenomenon and radio galaxies. These new observations probe the molecular gas
distribution and obscured nuclear regions of PKS 1345+12 and provide
morphological support for the idea that the radio activity in powerful radio
galaxies is triggered by the merger of gas rich galaxies. Two nuclei separated
by 2" (4.0 kpc) are observed in the near-infrared; the extended southeastern
nucleus has colors consistent with reddened starlight, and the compact
northwestern nucleus has extremely red colors indicative of an optical quasar
with a warm dust component. Further, the molecular gas, 3mm continuum, and
radio emission are coincident with the redder nucleus, confirming that the
northwestern nucleus is the site of the AGN and that the molecular gas is the
likely fuel source.Comment: LaTex, 5 pages with 1 postscript and 1 jpg figure, ApJ Letters, in
press (August 20, 1999
The Circum-Galactic Environment of Bright IRAS Galaxies
This paper studies systematically, for the first time, the circumgalactic
environment of bright IRAS galaxies as defined by Soifer et al. (1989). While
the role of gravitational interaction for luminous and ultraluminous IRAS
galaxies has been well established by various studies, the situation is by far
more obscure in the IR luminosity range of the bright IRAS sample, 10^{10}Lsol
< Lfir < 10^{11} Lsol. To easily identify nearby companion galaxies, the bright
IRAS sample was restricted to 87 objects with redshift range 0.008 < z < 0.018
and galactic latitude > 30^{o}. A control sample, selected from the Center for
Astrophysics redshift survey catalogue, includes 90 objects matching the Bright
IRAS sample for distribution of isophotal diameter, redshift, and morphological
type. From a search of nearby companion galaxies within 250 Kpc on the
second-generation Digitized Sky Survey (DSS-II), we found that the
circumgalactic environment of the Bright IRAS galaxies contains more large
companions than the galaxies in the optically selected control sample, and is
similar to that of Seyfert 2 galaxies. We found a weak correlation over a wide
range of far IR luminosity (10^9 Lsol < Lfir < 10^{12.5}Lsol) between projected
separation and Lfir, which confirms a very close relationship between star
formation rate of a galaxy and the strength of gravitational perturbations. We
also find that the far IR colors depend on whether a source is isolated or
interacting. Finally, we discuss the intrinsic difference and evolution
expectations for the bright IRAS galaxies and the control sample, as well as
the relationship between starbursting and active galaxies.Comment: 10 pages, 5 figs, 2 tables. Accepted for publication in Ap
Imaging of Ultraluminous Infrared Galaxies in the Near-UV
We present the first ground-based U' (3410 angstroms) images of Ultraluminous
Infrared Galaxies (ULIGs). Strong U' emission (median total M_U' = -20.8) is
seen in all systems and in some cases the extended tidal features (both the
smooth stellar distribution and compact star-forming features) contribute up to
60-80% of the total flux. The star-forming regions in both samples are found to
have ages based on spectral synthesis models in the range 10-100 Myrs, and most
differences in color between them can be attributed to the effects of dust
reddening. Additionally, it is found that star-formation in compact knots in
the tidal tails is most prominent in those ULIGs which have double nuclei,
suggesting that the star-formation rate in the tails peaks prior to the actual
coalescence of the galaxy nuclei and diminishes quickly thereafter. Similar to
results at other wavelengths, the observed star formation at U' can only
account for a small fraction of the known bolometric luminosity of the ULIGs.
Azimuthally averaged radial light profiles at U' are characterized by a sersic
law with index n=2, which is intermediate between an exponential disk and an
r^(-1/4) law and closely resembles the latter at large radii. The implications
of this near-ultraviolet imaging for optical/near-infrared observations of high
redshift counterparts of ULIGs are discussed.Comment: 30 pages, 4 tables, and 9 figures, 2 of which are JPEGs. To appear in
the August, 2000 edition of the Astronomical Journa
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