7,041 research outputs found
Ionized gas outflows in infrared-bright dust-obscured galaxies selected with WISE and SDSS
We present the ionized gas properties of infrared (IR)-bright dust-obscured
galaxies (DOGs) that show an extreme optical/IR color, , selected with the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared
Survey Explorer (WISE). For 36 IR-bright DOGs that show [OIII]5007
emission in the SDSS spectra, we performed a detailed spectral analysis to
investigate their ionized gas properties. In particular, we measured the
velocity offset (the velocity with respect to the systemic velocity measured
from the stellar absorption lines) and the velocity dispersion of the [OIII]
line. We found that the derived velocity offset and dispersion of most
IR-bright DOGs are larger than those of Seyfert 2 galaxies (Sy2s) at ,
meaning that the IR-bright DOGs show relatively strong outflows compared to
Sy2s. This can be explained by the difference of IR luminosity contributed from
active galactic nucleus, (AGN), because we found that (i) (AGN) correlates with the velocity offset and dispersion of [OIII] and
(ii) our IR-bright DOGs sample has larger (AGN) than Sy2s.
Nevertheless, the fact that about 75% IR-bright DOGs have a large ( 300 km
s) velocity dispersion, which is a larger fraction compared to other AGN
populations, suggests that IR-bright DOGs are good laboratories to investigate
AGN feedback. The velocity offset and dispersion of [OIII] and
[NeIII]3869 are larger than those of [OII]3727, which
indicates that the highly ionized gas tends to show more stronger outflows.Comment: 19 pages, 16 figures, and 2 tables, accepted for publication in Ap
How frequent are close supermassive binary black holes in powerful jet sources?
24 pages, 36 figures. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)Supermassive black hole binariesmay be detectable by an upcoming suite of gravitationalwave experiments. Their binary nature can also be revealed by radio jets via a short-period precession driven by the orbital motion as well as the geodetic precession at typically longer periods. We have investigated Karl G. Jansky Very Large Array and Multi-Element Radio Linked Interferometer Network (MERLIN) radio maps of powerful jet sources for morphological evidence of geodetic precession. For perhaps the best-studied source, Cygnus A, we find strong evidence for geodetic precession. Projection effects can enhance precession features, for which we find indications in strongly projected sources. For a complete sample of 33 3CR radio sources, we find strong evidence for jet precession in 24 cases (73 per cent). The morphology of the radio maps suggests that the precession periods are of the order of 10 6- 10 7 yr. We consider different explanations for the morphological features and conclude that geodetic precession is the best explanation. The frequently observed gradual jet angle changes in samples of powerful blazars can be explained by orbital motion. Both observations can be explained simultaneously by postulating that a high fraction of powerful radio sources have subparsec supermassive black hole binaries.We consider complementary evidence and discuss if any jetted supermassive black hole with some indication of precession could be detected as individual gravitational wave source in the near future. This appears unlikely, with the possible exception of M87.Peer reviewedFinal Published versio
Feedback from low-luminosity radio galaxies:B2 0258+35
Low-luminosity radio-loud active galactic nuclei (AGN) are of importance in
studies concerning feedback from radio AGN since a dominant fraction of AGN
belong to this class. We report high-resolution Very Large Array (VLA) and
European VLBI Network (EVN) observations of HI-21cm absorption from a young,
compact steep-spectrum radio source, B2 0258+35, nested in the early-type
galaxy NGC 1167, which contains a 160 kpc HI disc. Our VLA and EVN HI
absorption observations, modelling, and comparison with molecular gas data
suggest that the cold gas in the centre of NGC 1167 is very turbulent (with a
velocity dispersion of ~ 90 km/s) and that this turbulence is induced by the
interaction of the jets with the interstellar medium (ISM). Furthermore, the
ionised gas in the galaxy shows evidence of shock heating at a few kpc from the
radio source. These findings support the results from numerical simulations of
radio jets expanding into a clumpy gas disc, which predict that the radio jets
in this case percolate through the gas disc and drive shocks into the ISM at
distances much larger than their physical extent. These results expand the
number of low-luminosity radio sources found to impact the surrounding medium,
thereby highlighting the possible relevance of these AGN for feedback.Comment: 11 pages, 9 figures; Accepted for publication in Astronomy &
Astrophysic
Modelling observable signatures of jet-ISM interaction: thermal emission and gas kinematics
Relativistic jets are believed to have a substantial impact on the gas
dynamics and evolution of the interstellar medium (ISM) of their host galaxies.
In this paper, we aim to draw a link between the simulations and the observable
signatures of jet-ISM interactions by analyzing the emission morphology and gas
kinematics resulting from jet-induced shocks in simulated disc and spherical
systems. We find that the jet-induced laterally expanding forward shock of the
energy bubble sweeping through the ISM causes large-scale outflows, creating
shocked emission and high-velocity dispersion in the entire nuclear regions
( kpcs) of their hosts. The jetted systems exhibit larger velocity
widths (> 800 km/s), broader Position-Velocity maps and distorted symmetry in
the disc's projected velocities than systems without a jet. We also investigate
the above quantities at different inclination angles of the observer with
respect to the galaxy. Jets inclined to the gas disc of its host are found to
be confined for longer times, and consequently couple more strongly with the
disc gas. This results in prominent shocked emission and high-velocity widths,
not only along the jet's path, but also in the regions perpendicular to them.
Strong interaction of the jet with a gas disc can also distort its morphology.
However, after the jets escape their initial confinement, the jet-disc coupling
is weakened, thereby lowering the shocked emission and velocity widths.Comment: Matches the Published versio
A search for broad infrared recombination lines in NGC 1068
We report infrared spectroscopy of the prototypical Seyfert 2 galaxy NGC
1068, aiming at detection of broad components of hydrogen recombination lines
that originate in the obscured broad-line region. Using the Short Wavelength
Spectrometer on board the Infrared Space Observatory, we have observed for the
first time the regions of Brackett beta 2.626um and Pfund alpha 7.460um, and
present improved data for Brackett alpha 4.052um. No significant broad
components are detected, implying an equivalent visual extinction to the
broad-line region of at least 50 magnitudes and an obscuring column density of
at least 10^23 cm^-2. While consistent with a highly obscured broad-line
region, as required by the classical unified scenario, these limits are not yet
significant enough to discriminate strongly between different torus models or
to constrain properties of the gas causing the very large X-ray obscuration. We
discuss the systematic limitations of infrared broad-line region searches and
suggest that Brackett alpha may often be the most favorable transition for
future searches.Comment: aastex (V4), 4 eps figures. Accepted by Ap
Assessment of Fibrinogen Macromolecules Interaction with Red Blood Cells Membrane by Means of Laser Aggregometry, Flow Cytometry, and Optical Tweezers Combined with Microfluidics
An elevated concentration of fibrinogen in blood is a significant risk factor during many
pathological diseases, as it leads to an increase in red blood cells (RBC) aggregation, resulting in
hemorheological disorders. Despite the biomedical importance, the mechanisms of fibrinogen-induced
RBC aggregation are still debatable. One of the discussed models is the non-specific adsorption of
fibrinogen macromolecules onto the RBC membrane, leading to the cells bridging in aggregates.
However, recent works point to the specific character of the interaction between fibrinogen and the RBC
membrane. Fibrinogen is the major physiological ligand of glycoproteins receptors IIbIIIa (GPIIbIIIa
or αIIÎČÎČ3 or CD41/CD61). Inhibitors of GPIIbIIIa are widely used in clinics for the treatment of
various cardiovascular diseases as antiplatelets agents preventing the plateletsâ aggregation. However,
the effects of GPIIbIIIa inhibition on RBC aggregation are not sufficiently well studied. The objective
of the present work was the complex multimodal in vitro study of the interaction between fibrinogen
and the RBC membrane, revealing the role of GPIIbIIIa in the specificity of binding of fibrinogen by the
RBC membrane and its involvement in the cellsâ aggregation process. We demonstrate that GPIIbIIIa
inhibition leads to a significant decrease in the adsorption of fibrinogen macromolecules onto the
membrane, resulting in the reduction of RBC aggregation. We show that the mechanisms underlying
these effects are governed by a decrease in the bridging components of RBC aggregation forces
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