1,515 research outputs found
Multifrequency study of a new Hybrid Morphology Radio Source
Hybrid Morphology Radio Sources (HyMoRS) are a class of radio galaxies having
the lobe morphology of a Fanaroff-Riley (FR) type I on one side of the active
nucleus and of a FR type II on the other. The origin of the different
morphologies between FR I and FR II sources has been widely discussed in the
past 40 years, and HyMoRS may be the best way to understand whether this
dichotomy is related to the intrinsic nature of the source and/or to its
environment. However, these sources are extremely rare (<1% of radio galaxies)
and only for a few of them a detailed radio study, that goes beyond the
morphological classification, has been conducted. In this paper we report the
discovery of one new HyMoRS; we present X-ray and multi-frequency radio
observations. We discuss the source morphological, spectral and polarisation
properties and confirm that HyMoRS are intrinsically bimodal with respect to
these observational characteristics. We notice that HyMoRS classification based
just on morphological properties of the source is hazardous.Comment: 8 pages, 9 figures, accepted MNRA
Les villes des nouveaux LÀnder : La requalification dans le difficile contexte du déclin
La question de la requalification des friches dans les villes des nouveaux LĂ€nder allemands se joue dans une situation dĂ©mographique difficile, quâaccompagne un contexte Ă©conomique peu favorable. Les friches sont nombreuses, et dâautres vont venir sâajouter au fur et Ă mesure des nĂ©cessaires dĂ©molitions : on comprend alors la nĂ©cessitĂ© pour les acteurs dâintĂ©grer la question des friches dans un processus global de restructuration du tissu urbain. Les marges de manoeuvre sont faibles pour tous les acteurs, qui doivent coordonner des intĂ©rĂȘts parfois difficilement conciliables : la transformation du bĂąti urbain est donc un processus lent, de longue haleine.The matter of retraining urban wasteland in german new LĂ€nder towns happens to occur at a time when demography is faced with a sharp drop. This is underscored by unfavourable economic conditions at that. There are plenty of urban wasteland and many others are looming because of the demolition work that needs to be done. One understands then how necessary it is for the participants to integrate the matter of urban wasteland into the process of urban tissue restructuring. The whole participants have little room for manoeuvre the more so as conflicting interests make it difficult to reach a compromise : the rehabilitation of urban tissue is therefore a slow, a long-term process
LLAGN and jet-scaling probed with the EVN
Accreting black holes on all mass scales (from stellar to supermassive)
appear to follow a nonlinear relation between X-ray luminosity, radio
luminosity and BH mass, indicating that similar physical processes drive the
central engines in X-ray binaries and active galactic nuclei (AGN). However, in
recent years an increasing number of BH systems have been identified that do
not fit into this scheme. These outliers may be the key to understand how BH
systems are powered by accretion. Here we present results from EVN observations
of a sample of low-luminosity AGN (LLAGN) with known mass that have unusually
high radio powers when compared with their X-ray luminosity.Comment: Presented at the 11th EVN Symposium, Bordeaux, France, 2012 October
9-12. Six pages, including a figure and a table. Final, accepted versio
Discovery of a radio relic in the low mass, merging galaxy cluster PLCK G200.9-28.2
Radio relics at the peripheries of galaxy clusters are tracers of the elusive
cluster merger shocks. We report the discovery of a single radio relic in the
galaxy cluster PLCK G200.9-28.2 (, ) using the Giant Metrewave Radio Telescope at 235 and 610 MHz and
the Karl G. Jansky Very Large Array at 1500 MHz. The relic has a size of Mpc, an arc-like morphology and is located at 0.9 Mpc from the
X-ray brightness peak in the cluster. The integrated spectral index of the
relic is . The spectral index map between 235 and 610 MHz shows
steepening from the outer to the inner edge of the relic in line with the
expectation from a cluster merger shock. Under the assumption of diffusive
shock acceleration, the radio spectral index implies a Mach number of
for the shock. The analysis of archival XMM Newton data shows that
PLCK G200.9-28.2 consists of a northern brighter sub-cluster, and a southern
sub-cluster in a state of merger. This cluster has the lowest mass among the
clusters hosting single radio relics. The position of the Planck Sunyaev
Ze'ldovich effect in this cluster is offset by 700 kpc from the X-ray peak in
the direction of the radio relic, suggests a physical origin for the offset.
Such large offsets in low mass clusters can be a useful tool to select
disturbed clusters and to study the state of merger.Comment: 10 pages, 7 figures, 4 tables. Accepted for publication in MNRA
Abell 1033: birth of a radio phoenix
Extended steep-spectrum radio emission in a galaxy cluster is usually
associated with a recent merger. However, given the complex scenario of galaxy
cluster mergers, many of the discovered sources hardly fit into the strict
boundaries of a precise taxonomy. This is especially true for radio phoenixes
that do not have very well defined observational criteria. Radio phoenixes are
aged radio galaxy lobes whose emission is reactivated by compression or other
mechanisms. Here, we present the detection of a radio phoenix close to the
moment of its formation. The source is located in Abell 1033, a peculiar galaxy
cluster which underwent a recent merger. To support our claim, we present
unpublished Westerbork Synthesis Radio Telescope and Chandra observations
together with archival data from the Very Large Array and the Sloan Digital Sky
Survey. We discover the presence of two sub-clusters displaced along the N-S
direction. The two sub-clusters probably underwent a recent merger which is the
cause of a moderately perturbed X-ray brightness distribution. A steep-spectrum
extended radio source very close to an AGN is proposed to be a newly born radio
phoenix: the AGN lobes have been displaced/compressed by shocks formed during
the merger event. This scenario explains the source location, morphology,
spectral index, and brightness. Finally, we show evidence of a density
discontinuity close to the radio phoenix and discuss the consequences of its
presence.Comment: accepted MNRA
Fitness costs associated with building and maintaining the burying beetle's carrion nest
It is well-known that features of animal nest architecture can be explained by fitness benefits gained by the offspring housed within. Here we focus on the little-tested suggestion that the fitness costs associated with building and maintaining a nest should additionally account for aspects of its architecture. Burying beetles prepare an edible nest for their young from a small vertebrate carcass, by ripping off any fur or feathers and rolling the flesh into a rounded ball. We found evidence that only larger beetles are able to construct rounder carcass nests, and that rounder carcass nests are associated with lower maintenance costs. Offspring success, however, was not explained by nest roundness. Our experiment thus provides rare support for the suggestion that construction and maintenance costs are key to understanding animal architecture.Cambridge Trust, CONACyT, European Research Council (Consolidators Grant ID: 310785 BALDWINIAN_BEETLES), Royal Society (Wolfson Merit Award), Natural Environment Research Council (Grant ID: NE/H019731/1
Discovery of the supernova remnant G351.0-5.4
Context. While searching the NRAO VLA Sky Survey (NVSS) for diffuse radio
emission, we have serendipitously discovered extended radio emission close to
the Galactic plane. The radio morphology suggests the presence of a previously
unknown Galactic supernova remnant. An unclassified {\gamma}-ray source
detected by EGRET (3EG J1744-3934) is present in the same location and may stem
from the interaction between high-speed particles escaping the remnant and the
surrounding interstellar medium.
Aims. Our aim is to confirm the presence of a previously unknown supernova
remnant and to determine a possible association with the {\gamma}-ray emission
3EG J1744-3934.
Methods. We have conducted optical and radio follow-ups of the target using
the Dark Energy Camera (DECam) on the Blanco telescope at Cerro Tololo
Inter-American Observatory (CTIO) and the Giant Meterwave Radio Telescope
(GMRT). We then combined these data with archival radio and {\gamma}-ray
observations.
Results. While we detected the extended emission in four different radio
bands (325, 1400, 2417, and 4850 MHz), no optical counterpart has been
identified. Given its morphology and brightness, it is likely that the radio
emission is caused by an old supernova remnant no longer visible in the optical
band. Although an unclassified EGRET source is co-located with the supernova
remnant, Fermi-LAT data do not show a significant {\gamma}-ray excess that is
correlated with the radio emission. However, in the radial distribution of the
{\gamma}-ray events, a spatially extended feature is related with SNR at a
confidence level {\sigma}.
Conclusions. We classify the newly discovered extended emission in the radio
band as the old remnant of a previously unknown Galactic supernova: SNR
G351.0-5.4.Comment: 6 pages, 6 figures, accepted A&
Radio Observations of HD80606 Near Planetary Periastron: II. LOFAR Low Band Antenna Observations at 30-78 MHz
All the giant planets in the solar system generate radio emission via the
electron cyclotron maser instability, most notably giving rise to Jupiter's
decametric emissions. An interaction with the solar wind is at least partially
responsible for all of these solar system electron cyclotron masers. HD80606b
is a giant planet with a highly eccentric orbit, leading to predictions that
its radio emission may be enhanced substantially near periastron. This paper
reports observations with the Low Frequency Array (LOFAR) of HD80606b near its
periastron in an effort to detect radio emissions generated by an electron
cyclotron maser instability in the planet's magnetosphere. The reported
observations are at frequencies between 30 MHz and 78 MHz, and they are
distinguished from most previous radio observations of extrasolar planets by
two factors: (i) They are at frequencies near 50 MHz, much closer to the
frequencies at which Jupiter emits (< 40 MHz) and lower than most previously
reported observations of extrasolar planets; and (ii) Sensitivities of
approximately a few millijanskys have been achieved, an order of magnitude or
more below nearly all previous extrasolar planet observations below 100 MHz. We
do not detect any radio emissions from HD80606b and use these observations to
place new constraints on its radio luminosity. We also revisit whether the
observations were conducted at a time when it was super-Alfvenic relative to
the host star's stellar wind, which experience from the solar system
illustrates is a state in which an electron cyclotron maser emission can be
sustained in a planet's magnetic polar regions.Comment: 7 pages, 2 figures, accepted A&
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