Interpreting radiative efficiency in radio-loud AGNs

Author submitted version of unrefereed Nature Astronomy comment. Version in journal format available at https://rdcu.be/KH6WRadiative efficiency in radio-loud active galactic nuclei is governed by the accretion rate onto the central black hole rather than directly by the type of accreted matter; while it correlates with real differences in host galaxies and environments, it does not provide unambiguous information about particular objects.Non peer reviewedFinal Accepted Versio

Extended X-ray emission around four 3C quasars at 0.55<z<0.75 observed with Chandra

We report on the detection of a soft spatially-extended component of X-ray emission around four intermediate-redshift 3C quasars observed with Chandra: 3C254, 3C263, 3C275.1 and 3C281. The bolometric luminosity of this emission ranges over 0.3-1.6 times 10^{44}erg/s, and extends to lengthscales of over 350 kpc at the redshift of the quasar. The X-rays are most likely thermal emission from the intracluster medium of a cluster of galaxies around each quasar, which provides the working surface for the powerful radio lobes. Some X-ray emission is also seen to be associated with the radio plasma.Comment: 8 pages, 4 panelled figures, MNRAS in pres

A Chandra study of particle acceleration in the multiple hotspots of nearby radio galaxies

We present Chandra observations of a small sample of nearby classical double radio galaxies which have more than one radio hotspot in at least one of their lobes. The X-ray emission from the hotspots of these comparatively low-power objects is expected to be synchrotron in origin, and therefore to provide information about the locations of high-energy particle acceleration. In some models of the relationship between the jet and hotspot the hotspots that are not the current jet termination point should be detached from the energy supply from the active nucleus and therefore not capable of accelerating particles to high energies. We find that in fact some secondary hotspots are X-ray sources, and thus probably locations for high-energy particle acceleration after the initial jet termination shock. In detail, though, we show that the spatial structures seen in X-ray are not consistent with naive expectations from a simple shock model: the current locations of the acceleration of the highest-energy observable particles in powerful radio galaxies need not be coincident with the peaks of radio or even optical emission.Comment: Accepted for ApJ. 33 pages, 8 figures inc. 2 in colo

SZ effect from radio-galaxy lobes: astrophysical and cosmological relevance

We derive the SZ effect arising in radio-galaxy lobes that are filled with high-energy, non-thermal electrons. We provide here quantitative estimates for SZ effect expected from the radio galaxy lobes by normalizing it to the Inverse-Compton light, observed in the X-ray band, as produced by the extrapolation to low energies of the radio emitting electron spectrum in these radio lobes. We compute the spectral and spatial characteristics of the SZ effect associated to the radio lobes of two distant radio galaxies (3C294 and 3C432) recently observed by Chandra, and we further discuss its detectability with the next generation microwave and sub-mm experiments with arcsec and $\sim \mu$K sensitivity. We finally highlight the potential use of the SZE from radio-galaxy lobes in the astrophysical and cosmological context.Comment: 8 pages, 5 figures, MNRAS in pres

Focusing on the extended X-ray emission in 3C 459 with a Chandra follow-up observation

6 pages, 4 figures. Reproduced with permission from Astronomy & Astrophysics. © 2019 ESO.Aims. We investigated the X-ray emission properties of the powerful radio galaxy 3C 459 revealed by a recent Chandra follow-up observation carried out in October 2014 with a 62 ks exposure. Methods. We performed an X-ray spectral analysis from a few selected regions on an image obtained from this observation and also compared the X-ray image with a 4.9 GHz VLA radio map available in the literature. Results. The dominant contribution comes from the radio core but significant X-ray emission is detected at larger angular separations from it, surrounding both radio jets and lobes. According to a scenario in which the extended X-ray emission is due to a plasma collisionally heated by jet-driven shocks and not magnetically dominated, we estimated its temperature to be ∼0.8 keV. This hot gas cocoon could be responsible for the radio depolarization observed in 3C 459, as recently proposed also for 3C 171 and 3C 305. On the other hand, our spectral analysis and the presence of an oxygen K edge, blueshifted at 1.23 keV, cannot exclude the possibility that the X-ray radiation originating from the inner regions of the radio galaxy could be intercepted by some outflow of absorbing material intervening along the line of sight, as already found in some BAL quasars.Peer reviewe

Adiabatic relativistic models for the jets in the radio galaxy 3C 31

We present a general approach to the modelling of the brightness and polarization structures of adiabatic, decelerating relativistic jets, based on the formalism of Matthews & Scheuer (1990). We compare the predictions of adiabatic jet models with deep, high-resolution observations of the radio jets in the FR I radio galaxy 3C 31. Adiabatic models require coupling between the variations of velocity, magnetic field and particle density. They are therefore more tightly constrained than the models previously presented for 3C 31 by Laing & Bridle (2002). We show that adiabatic models provide a poorer description of the data in two crucial respects: they cannot reproduce the observed magnetic-field structures in detail, and they also predict too steep a brightness decline along the jets for plausible variations of the jet velocity. We find that the innermost regions of the jets show the strongest evidence for non-adiabatic behaviour, and that the adiabatic models provide progressively better descriptions of the jet emission at larger distances from the galactic nucleus. We briefly discuss physical processes which might contribute to this non-adiabatic behaviour. In particular, we develop a parameterized description of distributed particle injection, which we fit to the observed total intensities. We show that particles are preferentially injected where bright X-ray emission is observed, and where we infer that the jets are over-pressured.Comment: 16 pages, 11 figures, accepted for publication in MNRA

Anisotropic inverse Compton emission in the radio galaxy 3C 265

We present the results from a Chandra observation of the powerful radio galaxy 3C 265. We detect X-ray emission from the nucleus, the radio hotspots and lobes. In particular, the lobe X-ray emission is well explained as anisotropic inverse Compton scattering of the nuclear photons by the relativistic electrons in the radio lobes; the comparison between radio synchrotron and IC emission yields a magnetic field strength a factor about 2 lower than that calculated under minimum energy conditions. The X-ray spectrum of the nucleus is consistent with that of a powerful, strongly absorbed quasar and the X-ray emission of the south-eastern hotspot can be successfully reproduced by a combination of synchro-self Compton and inverse Compton emission assuming a magnetic field slightly lower than equipartition.Comment: 5 pages, 6 figures, to be published as a Letter on Monthly Notices of the Royal Astronomical Societ

On voxel-by-voxel accumulated dose for prostate radiation therapy using deformable image registration.

Since delivered dose is rarely the same with planned, we calculated the delivered total dose to ten prostate radiotherapy patients treated with rectal balloons using deformable dose accumulation (DDA) and compared it with the planned dose. The patients were treated with TomoTherapy using two rectal balloon designs: five patients had the Radiadyne balloon (balloon A), and five patients had the EZ-EM balloon (balloon B). Prostate and rectal wall contours were outlined on each pre-treatment MVCT for all patients. Delivered fractional doses were calculated using the MVCT taken immediately prior to delivery. Dose grids were accumulated to the last MVCT using DDA tools in Pinnacle3 TM (v9.100, Philips Radiation Oncology Systems, Fitchburg, USA). Delivered total doses were compared with planned doses using prostate and rectal wall DVHs. The rectal NTCP was calculated based on total delivered and planned doses for all patients using the Lyman model. For 8/10 patients, the rectal wall NTCP calculated using the delivered total dose was less than planned, with seven patients showing a decrease of more than 5% in NTCP. For 2/10 patients studied, the rectal wall NTCP calculated using total delivered dose was 2% higher than planned. This study indicates that for patients receiving hypofractionated radiotherapy for prostate cancer with a rectal balloon, total delivered doses to prostate is similar with planned while delivered dose to rectal walls may be significantly different from planned doses. 8/10 patients show significant correlation between rectal balloon anterior-posterior positions and some VD values

Internal entrainment and the origin of jet-related broad-band emission in Centaurus A

Date of Acceptance: 14/11/2014The dimensions of Fanaroff-Riley class I jets and the stellar densities at galactic centres imply that there will be numerous interactions between the jet and stellar winds. These may give rise to the observed diffuse and 'knotty' structure of the jets in the X-ray, and can also mass load the jets. We performed modelling of internal entrainment from stars intercepted by Centaurus A's jet, using stellar evolution- and wind codes. From photometry and a codesynthesized population of 12 Gyr (Z = 0.004), 3 Gyr (Z = 0.008) and 0-60 Myr (Z = 0.02) stars, appropriate for the parent elliptical NGC 5128, the total number of stars in the jet is ∼8 × 108. Our model is energetically capable of producing the observed X-ray emission, even without young stars. We also reproduce the radio through X-ray spectrum of the jet, albeit in a downstream region with distinctly fewer young stars, and recover the mean X-ray spectral index.We derive an internal entrainment rate of ∼2.3 × 10-3M yr-1 which implies substantial jet deceleration. Our absolute nucleosynthetic yields for the Asymptotic Giant Branch stellar population in the jet show the highest amounts for 4He, 16O, 12C, 14N and 20Ne. If some of the events at ≥55 EeV detected by the Pierre Auger Observatory originate from internal entrainment in Centaurus A, we predict that their composition will be largely intermediate-mass nuclei with 16O, 12C and 14N the key isotopes.Peer reviewe

Empirical Bayesian analysis of paired high-throughput sequencing data with a beta-binomial distribution.

BACKGROUND: Pairing of samples arises naturally in many genomic experiments; for example, gene expression in tumour and normal tissue from the same patients. Methods for analysing high-throughput sequencing data from such experiments are required to identify differential expression, both within paired samples and between pairs under different experimental conditions. RESULTS: We develop an empirical Bayesian method based on the beta-binomial distribution to model paired data from high-throughput sequencing experiments. We examine the performance of this method on simulated and real data in a variety of scenarios. Our methods are implemented as part of the RbaySeq package (versions 1.11.6 and greater) available from Bioconductor (http://www.bioconductor.org). CONCLUSIONS: We compare our approach to alternatives based on generalised linear modelling approaches and show that our method offers significant gains in performance on simulated data. In testing on real data from oral squamous cell carcinoma patients, we discover greater enrichment of previously identified head and neck squamous cell carcinoma associated gene sets than has previously been achieved through a generalised linear modelling approach, suggesting that similar gains in performance may be found in real data. Our methods thus show real and substantial improvements in analyses of high-throughput sequencing data from paired samples.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are