100 research outputs found
Millimeter observations of radio-loud active galaxies
In order to study the nature of the far-infrared emission observed in
radio-loud active galaxies, we have obtained 1.2 mm observations with the IRAM
30 m telescope for a sample of eight radio-loud active galaxies. In all objects
we find that the 1.2 mm emission is dominated by non-thermal emission. An
extrapolation of the non-thermal radio spectrum indicates that the contribution
of synchrotron emission to the far-infrared is less than 10% in quasars, and
negligible in the radio galaxies. The quasars in the sample show signs of
relativistic beaming at millimeter wavelengths, and the quasar 3C334 shows
evidence for strong variability.Comment: 6 pages, 1 figure, accepted by A&
A relation between circumnuclear HI, dust, and optical cores in low-power radio galaxies
From new observations and literature data we investigate the presence of HI,
dust, and optical cores in the central kiloparsec of low-power radio galaxies.
The goal of this pilot study is to identify physical relations between these
components, which can help us to study kinematics and feeding mechanisms in
future samples of active galaxies. Our results are consistent with neutral gas
being associated with dust on sub-kiloparsec scales. Objects that have HI
absorption always have significant amounts of dust in their host galaxy. If
there is no visible dust in the host galaxy, there is also no HI absorption.
The presence of an unresolved optical core correlates with the HI column
density, with the core being absent in high column density sources. This work
opens a path for studying the kinematics of cold material in the central
regions of active galaxies by combining information of HI absorption and
molecular lines. Consistent with previous work, we find no evidence for a
compact, parsec-scale obscuring torus in low-power radio galaxies.Comment: Accepted for publication in A&
e-EVN detection of AGN activity in NGC 2617
NGC 2617 is a Seyfert 1.8 spiral galaxy at z=0.0142 (~60 Mpc, 1 mas = 0.3 pc) that is currently in outburst. We carried out European VLBI Network real-time e-VLBI observations at 1.6 GHz on 2013 June 7
Mid-frequency aperture arrays: the future of radio astronomy
Aperture array (AA) technology is at the forefront of new developments and
discoveries in radio astronomy. Currently LOFAR is successfully demonstrating
the capabilities of dense and sparse AA's at low frequencies. For the
mid-frequencies, from 450 to 1450MHz, AA's still have to prove their scientific
value with respect to the existing dish technology. Their large field-of-view
and high flexibility puts them in an excellent position to do so. The Aperture
Array Verification Program is dedicated to demonstrate the feasibility of AA's
for science in general and SKA in particular. For the mid-frequency range this
has lead to the development of EMBRACE, which has already demonstrated the
enormous flexibility of AA systems by observing HI and a pulsar simultaneously.
It also serves as a testbed to demonstrate the technological reliability and
stability of AA's. The next step will put AA technology at a level where it can
be used for cutting-edge science. In this paper we discuss the developments to
move AA technology from an engineering activity to a fully science capable
instrument. We present current results from EMBRACE, ongoing tests of the
system, and plans for EMMA, the next step in mid-frequency AA technology.Comment: 8 pages, 7 figures, proceedings of Resolving The Sky - Radio
Astronomy: Past, Present and Future (RTS2012), April 17-20, 2012, Manchester,
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