Radio galaxies are a subclass of active galactic nuclei (AGN) in which accretion onto the supermassive black hole releases energy into the environment via relativistic jets. The jets are not ...constantly active throughout the life of the host galaxy and alternate between active and quiescent phases. Remnant radio galaxies are detected during a quiescent phase and define a class of unique sources that can be used to constrain the AGN duty cycle. We present, for the first time, a spatially resolved radio analysis of the radio galaxy associated with the galaxy NGC 6086 down to 144 MHz and constraints on the spectral age of the diffuse emission to investigate the duty cycle and evolution of the source. We used three new low-frequency, high-sensitivity observations; the first was performed with the Low Frequency Array at 144 MHz and the other two with the upgraded Giant Metrewave Radio Telescope at 400 MHz and 675 MHz, respectively. To these, we add two Very Large Array archival observations at higher frequencies (1400 and 4700 MHz). In the new observations in the frequency range 144–675 MHz, we detect a second pair of larger lobes and three regions within the remnant emission with a filamentary morphology. We analysed the spectral index trend in the inner remnant lobes and see systematically steeper values (
α
low
∼1.1–1.3) at the lower frequencies compared to the gigahertz frequencies (
α
high
∼0.8–0.9). Steeper spectral indices are found in the newly detected outer lobes (up to
α
outer
∼2.1), as expected if they trace a previous phase of activity of the AGN. However, the differences between the spectra of the two outer lobes suggest different dynamical evolutions within the intra-group medium during their expansion and/or different magnetic field values. Using a single-injection radiative model and assuming equipartition conditions, we place constraints on the age of the inner and outer lobes and derive the duty cycle of the source. We estimate that the duration of the two active phases was 45 Myr and 18 Myr and the duration of the two inactive phases was 66 Myr and 33 Myr. This results in a total active time of
t
on
∼ 39%. The filamentary structures have a steep spectral index (∼1) without any spectral index trend, and only one of them shows a steepening in the spectrum. Their origin is not yet clear, but they may have formed due to the compression of the plasma or due to magnetic field substructures.
Aims. We recently performed a study of a sample of relaxed, cooling core galaxy clusters with deep Very Large Array observations at 1.4 GHz. We find that in the central regions of A1835, A2029, and ...Ophiuchus the dominant radio galaxy is surrounded by a diffuse low-brightness radio emission that takes the form of a mini-halo. Here we present the results of the analysis of the extended diffuse radio emission in these mini-halos. Methods. In order to investigate the morphological properties of the diffuse radio emission in clusters of galaxies we propose to fit their azimuthally averaged brightness profile with an exponential, obtaining the central brightness and the e-folding radius from which the radio emissivity can be calculated. We investigate the radio properties of the mini-halos in A1835, A2029, and Ophiuchus in comparison with the radio properties of a representative sample of mini-halos and halos already known in the literature. Results. We find that radio halos can have quite different length-scales but their emissivity is remarkably similar from one halo to the other. In contrast, mini-halos span a wide range of radio emissivity. Some of them, like the Perseus mini-halo, are characterized by a radio emissivity which is more than 100 times greater than that of radio halos. On the other hand, the new mini-halos in cooling core clusters analyzed in this work, namely A2029, Ophiuchus, and A1835, have a radio emissivity which is much more typical of halos in merging clusters rather than similar to that of the other mini-halos previously known.
ABSTRACT
The Main galaxy cluster in the Abell 781 system is undergoing a significant merger and accretion process with peripheral emission to the north and south-eastern flanks of the merging ...structure. Here we present a full polarimetric study of this field, using radio interferometric data taken at 21 and 92 cm with the Westerbork Synthesis Radio Telescope (WSRT), to a sensitivity better than any 21 cm (L band) observation to date. We detect evidence of extended low-level emission of 1.9 mJy associated with the Main cluster at 21 cm, although this detection necessitates further follow-up by modern instruments due to the limited resolution of the WSRT. Our polarimetric study indicates that, most likely, the peripheral emission associated with this cluster is not a radio relic.
Aims. Radio halos are faint radio sources usually located at the center of merging clusters of galaxies. These diffuse radio sources are rare, having so far been found only in about 30 clusters of ...galaxies, suggesting that particular conditions are needed to form and maintain them. It is interesting to investigate the presence of radio halos in close pairs of interacting clusters in order to possibly clarify their origin in relation to the evolutionary state of the merger. In this work, we study the case of the close pair of galaxy clusters A399 and A401. Methods. A401 is already known to contain a faint radio halo, while a hint of diffuse emission in A399 has been suggested based on the NVSS. To confirm this possibility, we analyzed deeper Very Large Array observations at 1.4 GHz of this cluster. Results. We find that the central region of A399 is permeated by a diffuse low-surface brightness radio emission that we classify as a radio halo with a linear size of about 570 kpc and a central brightness of 0.3 μJy/arcsec2. Indeed, given their comparatively small projected distance of ~3 Mpc, the pair of galaxy clusters A401 and A399 can be considered as the first example of double radio halo system. The discovery of this double halo is extraordinary given the rarity of these radio sources in general and given that current X-ray data seem to suggest that the two clusters are still in a pre-merger state. Therefore, the origin of the double radio halo is likely to be attributed to the individual merging histories of each cluster separately, rather than to the result of a close encounter between the two systems.
We have observed the Andromeda galaxy, Messier 31 (M31), at 6.7 GHz with the Sardinia Radio Telescope. We mapped the radio emission in the C-band, re-analyzed WMAP and Planck maps, as well as other ...ancillary data, and we have derived an overall integrated flux density spectrum from the radio to the infrared. This allowed us to estimate the emission budget from M31. Integrating over the whole galaxy, we found strong and highly significant evidence for anomalous microwave emission (AME), at the level of Jy at the peaking frequency of 25 GHz. Decomposing the spectrum into known emission mechanisms such as free-free, synchrotron, thermal dust, and AME arising from electric dipole emission from rapidly rotating dust grains, we found that the overall emission from M31 is dominated, at frequencies below 10 GHz, by synchrotron emission with a spectral index of , with subdominant free-free emission. At frequencies 10 GHz, AME has a similar intensity to that of synchrotron and free-free emission, overtaking them between 20 and 50 GHz, whereas thermal dust emission dominates the emission budget at frequencies above 60 GHz, as expected.
ABSTRACT
Numerical simulations offer the unique possibility to forecast the results of surveys and targeted observations that will be performed with next-generation instruments like the Square ...Kilometre Array. In this paper, we investigate for the first time how future radio surveys in polarization will be affected by confusion noise. To do this, we produce 1.4 GHz simulated full-Stokes images of the extragalactic sky by modelling various discrete radio sources populations. The results of our modelling are compared to data in the literature to check the reliability of our procedure. We also estimate the number of polarized sources detectable by future surveys. Finally, from the simulated images we evaluate the confusion limits in I, Q, and U Stokes parameters, giving analytical formulas of their behaviour as a function of the angular resolution.
We study the structure of the galaxy cluster Abell 523 (A523) at z = 0.104 using new spectroscopic data for 132 galaxies acquired at the Telescopio Nazionale Galileo, new photometric data from the ...Isaac Newton Telescope, and X-ray and radio data from the Chandra and Very Large Array archives. We estimate the velocity dispersion of the galaxy population,
$\sigma _{\rm V}=949_{-60}^{+80}$
km s−1, and the X-ray temperature of the hot intracluster medium, kT = 5.3 ± 0.3 keV. We infer that A523 is a massive system: M
200 ∼ 7–9 × 1014 M⊙. The analysis of the optical data confirms the presence of two subclusters, 0.75 Mpc apart, tracing the SSW-NNE direction and dominated by the two brightest cluster galaxies (BCG1 and BCG2). The X-ray surface brightness is strongly elongated towards the NNE direction, and its peak is clearly offset from both the brightest cluster galaxies (BCGs). We confirm the presence of a 1.3 Mpc large radio halo, elongated in the ESE-WNW direction and perpendicular to the optical/X-ray elongation. We detect a significant radio/X-ray offset and radio polarization, two features which might be the result of a magnetic field energy spread on large spatial scales. A523 is found consistent with most scaling relations followed by clusters hosting radio haloes, but quite peculiar in the P
radio–L
X relation: it is underluminous in the X-rays or overluminous in radio. A523 can be described as a binary head-on merger caught after a collision along the SSW-NNE direction. However, minor optical and radio features suggest a more complex cluster structure, with A523 forming at the crossing of two filaments along the SSW-NNE and ESE-WNW directions.
New classes of chemistries are needed to control insecticide resistant populations of mosquitoes and prevent transmission of vector-borne diseases (VBDs). Organismal screens of chemical collections ...have played an important role in the search for new vector insecticides and the identification of active ingredients (AIs) that cause rapid mortality of mosquitoes. Advances in image-based screening offer an opportunity to identify chemistries that operate via novel biochemical modes and investigate the range of phenotypes exhibited by mosquitoes following exposure to lethal and sub-lethal chemical dose. An automated, high throughput phenotypic screen (HTS) employing high-content imaging of first instar (L1) Aedes aegypti larvae was developed to identify chemistries associated with mortality and atypical morphological phenotypes. A pilot screen of the Library of Pharmacologically Active Compounds (LOPAC1280) identified 92 chemistries that disrupted larval activity and development, including conventional insecticides and chemistries known to modulate G protein-coupled receptors (GPCRs) and other molecular targets in mammalian systems. Secondary assay series were used to evaluate a selection of chemistries for impacts on mosquito activity, survival and development. Ritodrine hydrochloride reduced mobility of larvae but had no observable effect on survival and development of mosquitoes. High doses of metergoline suppressed larval activity and sub-lethal dose resulted in pupal mortality. Assay data support the utility of phenotypic screening and diverse entomological end-points for discovery of novel insecticidal chemical scaffolds. The insecticide discovery process must consider how multi-modal efficacy spectra contribute to vector and VBD control.
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•An automated phenotypic screen was employed to find new mosquito-active chemistries.•High-content imaging detected larval movement and novel phenotypic endpoints.•Pilot screen uncovered chemistries that disrupted mosquito activity, development.•Assays confirmed insecticidal activity of GPCR modulators and other chemistries.•Screening regime revealed diverse chemistries and possible novel modes of action.
Context. Radio loud active galactic nuclei (AGN) are episodic in nature, cycling through periods of activity and quiescence. The study of this duty cycle has recently gained new relevance because of ...the importance of AGN feedback for galaxy evolution. Aims. In this work we investigate the duty cycle of the radio galaxy B2 0258+35, which was previously suggested to be a restarted radio galaxy based on its morphology. The radio source consists of a pair of kpc-scale jets embedded in two large-scale lobes (∼240 kpc) with relaxed shape and very low surface brightness, which resemble remnants of a past AGN activity. Methods. We have combined new LOFAR data at 145 MHz and new Sardinia Radio Telescope data at 6600 MHz with available WSRT data at 1400 MHz to investigate the spectral properties of the outer lobes and derive their age. Results. Interestingly, the spectrum of both the outer northern and southern lobes is not ultra-steep as expected for an old ageing plasma with spectral index values equal to α1451400 = 0.48 ± 0.11 α 1400 145 = 0.48 ± 0.11 ${\rm {\alpha}}_{1400}^{145} = 0.48 \pm 0.11$ and α14006600 = 0.69 ± 0.20 α 6600 1400 = 0.69 ± 0.20 ${\rm {\alpha}}_{6600}^{1400} {=} 0.69\pm0.20$ in the outer northern lobe, and α1451400 = 0.73 ± 0.07 α 1400 145 = 0.73 ± 0.07 ${\rm {\alpha}}_{1400}^{145} {=} 0.73\pm0.07$ in the outer southern lobe. Moreover, despite the wide frequency coverage available for the outer northern lobe (145–6600 MHz), we do not identify a significant spectral curvature (SPC ≃ 0.2 ± 0.2). Conclusions. While mechanisms such as in-situ particle reacceleration, mixing or compression can temporarily play a role in preventing the spectrum from steepening, in no case seem the outer lobes to be compatible with being very old remnants of past activity as previously suggested (with age ≳ 80 Myr). We conclude that either the large-scale lobes are still fuelled by the nuclear engine or the jets have switched off no more than a few tens of Myr ago, allowing us to observe both the inner and outer structure simultaneously. Our study shows the importance of combining morphological and spectral properties to reliably classify the evolutionary stage of low surface brightness, diffuse emission that low frequency observations are revealing around a growing number of radio sources.
We have developed a highly sensitive mass spectrometry‐based proteomic workflow to examine the proteome of single muscle fibers. This study revealed significant differences in the mitochondrial ...proteome of the four major fiber types present in mouse skeletal muscle. Here, we focus on Krebs cycle enzymes and in particular on the differential distribution of the two mitochondrial isocitrate dehydrogenases, IDH2 and IDH3. Type 1/slow fibers contain high levels of IDH2 and relatively low levels of IDH3, whereas fast 2X and 2B fibers show an opposite expression pattern. The findings suggest that in skeletal muscle, IDH2 functions in the forward direction of the Krebs cycle and that substrate flux along the cycle occurs predominantly via IDH2 in type 1 fibers and via IDH3 in 2X and 2B fibers. IDH2‐mediated conversion of isocitrate to α‐ketoglutarate leads to the generation of NADPH, which is critical to buffering the H2O2 produced by the respiratory chain. Nicotinamide nucleotide transhydrogenase (NNT), the other major mito‐chondrial enzyme involved in NADPH generation, is also more abundant in type 1 fibers. We suggest that the continuously active type 1 fibers are endowed with a more efficient H2O2 scavenging capacity to cope with the higher levels of reactive oxygen species production.
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