1,336 research outputs found
The jet-ISM interaction in the Outer Filament of Centaurus A
The interaction between the radio plasma ejected by the active nucleus of a
galaxy and the surrounding medium is a key process that can have a strong
impact on the interstellar medium of the galaxy and hence on galaxy evolution.
The closest laboratory where we can observe and investigate this phenomenon is
the radio galaxy Centaurus A. About 15 kpc north-east of this galaxy, a
particularly complex region is found: the so-called Outer Filament where
jet-cloud interactions have been proposed to occur. We investigate the presence
of signatures of jet-ISM interaction by a detailed study of the kinematics of
the ionized gas, expanding on previous results obtained from the HI. We
observed two regions of the outer filament with VLT/VIMOS in the IFU observing
mode. Emission from Hbeta and [OIII]4959,5007\AA\ is detected in both
pointings. We found two distinct kinematical components of ionized gas that
well match the kinematics of the nearby HI cloud. One component follows the
regular kinematics of the rotating gas while the second shows similar
velocities to those of the nearby HI component thought to be disturbed by an
interaction with the radio jet. We suggest that the ionized and atomic gas are
part of the same dynamical gas structure originating as result of the merger
that shaped Centaurus A and which is regularly rotating around Centaurus A as
proposed by other authors. The gas (ionized and HI) with anomalous velocities
is tracing the interaction of the Large-Scale radio Jet with the ISM,
suggesting that, although poorly collimated as structure, the jet is still
active. However, we can exclude that a strong shock is driving the ionization
of the gas. It is likely that a combination of jet entrainment and
photoionization by the UV continuum from the central engine is needed in order
to explain both the ionization and the kinematics of the gas in the Outer
Filament.Comment: 6 pages, 6 figures, 1 table. Final version accepted for publication
on A&
The fast molecular outflow in the Seyfert galaxy IC5063 as seen by ALMA
We use high-resolution (0.5 arcsec) CO(2-1) observations performed with ALMA
to trace the kinematics of the molecular gas in the Seyfert 2 galaxy IC5063. A
fast outflow of molecular gas extends along the entire radio jet, with the
highest outflow velocities about 0.5kpc from the nucleus, at the location of
the brighter hot-spot in the W lobe. The data show that a massive, fast outflow
with velocities up to 650 km/s of cold molecular gas is present, in addition to
one detected earlier in warm H2, HI and ionised gas. Both the central AGN and
the radio jet could energetically drive the outflow. However, the
characteristics of the outflowing gas point to the radio jet being the main
driver. This is important, because IC5063, although one of the most powerful
Seyfert galaxies, is a relatively weak radio source (P = 3x10^23 W/Hz). All the
observed characteristics can be described by a scenario of a radio plasma jet
expanding into a clumpy medium, interacting directly with the clouds and
inflating a cocoon that drives a lateral outflow into the interstellar medium.
This model is consistent with results obtained by recent simulations such as
those of Wagner et al.. A stronger, direct interaction between the jet and a
gas cloud is present at the location of the brighter W lobe. Even assuming the
most conservative values for the conversion factor CO-to-H2, the mass of the
outflowing gas is between 1.9 and 4.8x10^7 Msun. These amounts are much larger
than those of the outflow of warm gas (molecular and ionized) and somewhat
larger than of the HI outflow. This suggests that most of the observed cold
molecular outflow is due to fast cooling after being shocked. This gas is the
end product of the cooling process. Our CO observations demonstrate that fast
outflows of molecular gas can be driven by relativistic jets.Comment: Accepted for publication in A&A. 11 pages, 8 figure
The outer filament of Centaurus A as seen by MUSE
We investigate signatures of a jet-interstellar medium (ISM) interaction
using optical integral-field observations of the so-called outer filament near
Centaurus A, expanding on previous results obtained on a more limited area.
Using the Multi Unit Spectroscopic Explorer (MUSE) on the VLT during science
verification, we observed a significant fraction of the brighter emitting gas
across the outer filament. The ionized gas shows complex morphology with
compact blobs, arc-like structures and diffuse emission. Based on the
kinematics, we identified three main components. The more collimated component
is oriented along the direction of the radio jet. The other two components
exhibit diffuse morphology together with arc-like structures also oriented
along the radio jet direction. Furthermore, the ionization level of the gas is
found to decrease from the more collimated component to the more diffuse
components. The morphology and velocities of the more collimated component
confirm our earlier results that the outer filament and the nearby HI cloud are
likely partially shaped by the lateral expansion of the jet. The arc-like
structures embedded within the two remaining components are the clearest
evidence of a smooth jet-ISM interaction along the jet direction. This suggests
that, although poorly collimated, the radio jet is still active and has an
impact on the surrounding gas. This result indicates that the effect on the ISM
of even low-power radio jets should be considered when studying the influence
Active Galactic Nuclei can have on their host galaxy.Comment: 5 pages, 3 figures, Accepted for publication by A&
Publiek-private samenwerking
Samenwerking tussen overheidsorganisaties en het bedrijfsleven staat volop in de belangstelling! De laatste jaren hebben vele projecten gestalte gekregen via een publiek-privaat samenwerkingsverband. In het DIII gaat één van de seminars over dit fenomeen. Het onderstaande stuk zal kort de achtergrond en het begrip schetsen
Geloof in Europees burgerschap
Een aantal jaren geleden merkte de gewone burger vrij weinig van de Europese integratie. Dit gaat echter meer en meer veranderen en het verdrag van Maastricht zal hierop een grote invloed uitoefenen. Het onderstaande stuk gaat in op het begrip Europees burgerschap wat voor het eerst in het verdrag van Maastricht is vastgelegd
Scheiden doet leiden
De kop van dit artikel luidt "Scheiden doet leiden". Lees verder om er achter te komen of dit een goede benaming is of dat er beter "Scheiden doet lijden" had kunnen staan
Ritueel slachten
Het ritueel slachten tijdens islamitische offerdagen is niet een nieuw fenomeen in Nederland, maar staat wel meer en meer in de maatschappelijke belangstelling. Een vergelijking tussen de situatie tien jaar geleden en de huidige situatie
LOFAR observations of 4C+19.44. On the discovery of low frequency spectral curvature in relativistic jet knots
We present the first LOFAR observations of the radio jet in the quasar
4C+19.44 (a.k.a. PKS 1354+19) obtained with the long baselines. The achieved
resolution is very well matched to that of archival Jansky Very Large Array
(JVLA) observations at higher radio frequencies as well as the archival X-ray
images obtained with {\it Chandra}. We found that, for several knots along the
jet, the radio flux densities measured at hundreds of MHz lie well below the
values estimated by extrapolating the GHz spectra. This clearly indicates the
presence of spectral curvature. Radio spectral curvature has been already
observed in different source classes and/or extended radio structures and it
has been often interpreted as due to intrinsic processes, as a curved particle
energy distribution, rather than absorption mechanisms ({ Razin-Tsytovich}
effect, free-free or synchrotron self absorption to name a few). Here we
discuss our results according to the scenario where particles undergo
stochastic acceleration mechanisms also in quasar jet knots.Comment: 13 pages, 4 tables, 4 figures, pre-proof version, published on the
Astrophysical Journal (Harris, et al. 2019 ApJ, 873, 21
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