J. H. Croston
A5011817252- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Pulsars and Gravitational Waves Research
- Particle Accelerators and Free-Electron Lasers
- GNSS positioning and interference
- Cosmology and Gravitation Theories
- Dark Matter and Cosmic Phenomena
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Particle accelerators and beam dynamics
- Spectroscopy and Laser Applications
- Species Distribution and Climate Change
- Remote Sensing in Agriculture
- Advanced Measurement and Metrology Techniques
- Computational Physics and Python Applications
- Multidisciplinary Science and Engineering Research
The Open University
2017-2025
University of Southampton
2009-2017
University of Cambridge
2015-2016
University of Hertfordshire
2005-2010
CEA Paris-Saclay
2005-2006
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2005-2006
Service de Physique de l'État Condensé
2006
University of Bristol
2003-2005
(abridged) We investigate the regularity of cluster pressure profiles with REXCESS, a representative sample 33 local clusters observed XMM-Newton. The spans mass range 10^14 M_sun <M_500<10^15 M_sun. derive an average profile from observations scaled by and z according to standard self-similar model, find that dispersion about mean is remarkably low beyond 0.2R_500, but increases towards centre. Deviations are related both thermo-dynamical state cluster. Unrelaxed systems have systematically...
We examine the X-ray luminosity scaling relations of 31 nearby galaxy clusters from Representative <i>XMM-Newton <i/> Cluster Structure Survey (REXCESS). The objects are selected only in luminosity, optimally sampling cluster function. Temperatures range 2 to 9 keV, and there is no bias toward any particular morphological type. To reduce measurement scatter we extract pertinent values an aperture corresponding <i>R<i/><sub>500<sub/>, estimated using tight correlation between...
This White Paper, submitted to the recent ESA call for science themes define its future large missions, advocates need a transformational leap in our understanding of two key questions astrophysics: 1) How does ordinary matter assemble into scale structures that we see today? 2) do black holes grow and shape Universe? Hot gas clusters, groups intergalactic medium dominates baryonic content local Universe. To understand astrophysical processes responsible formation assembly these structures,...
The LOFAR Two-metre Sky Survey (LoTSS) is an ongoing sensitive, high-resolution 120-168MHz survey of the entire northern sky for which observations are now 20% complete. We present our first full-quality public data release. For this release 424 square degrees, or 2% eventual coverage, in region HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45$^\circ$00$'$00$''$ 57$^\circ$00$'$00$''$) were mapped using a fully automated direction-dependent calibration imaging...
(Abridged) We examine the radial entropy distribution and its scaling using 31 nearby galaxy clusters from Representative XMM-Newton Cluster Structure Survey (REXCESS). The profiles are robustly measured at least out to R_1000 in all systems R_500 13 systems. Compared theoretical expectations, observed distributions show a mass-dependent excess that is greater extends larger radii lower mass At R_500, dependence both negligible within uncertainties. Mirroring this behaviour, of gas shallower...
In this data release from the LOFAR Two-metre Sky Survey (LoTSS) we present 120-168MHz images covering 27% of northern sky. Our coverage is split into two regions centred at approximately 12h45m +44$^\circ$30' and 1h00m +28$^\circ$00' spanning 4178 1457 square degrees respectively. The were derived 3,451hrs (7.6PB) High Band Antenna which corrected for direction-independent instrumental properties as well direction-dependent ionospheric distortions during extensive, but fully automated,...
The relative positions of the high and low surface brightness regions radio-loud active galaxies in 3CR sample were found by Fanaroff Riley to be correlated with their luminosity. We revisit this canonical relationship a 5805 extended AGN from LOFAR Two-Metre Sky Survey (LoTSS), compiling most complete dataset radio-galaxy morphological information obtained date. demonstrate that, for sample, radio luminosity does *not* reliably predict whether source is edge-brightened (FRII) or...
We have recently shown that X-ray observations of the population ‘low-excitation’ radio galaxies, which includes most low-power, Fanaroff–Riley class I sources as well some more powerful II objects, are consistent with a model in active nuclei these objects not radiatively efficient at any waveband. In another recent paper, Allen et al. Bondi accretion hot, emitting phase intergalactic medium (IGM) is sufficient to power jets several nearby, low-power galaxies centres clusters. this we...
We present a Chandra and XMM-Newton study of X-ray emission from the lobes 33 classical double radio galaxies quasars. report new detections lobe-related in 11 sources. Together with previous detections, we find that is detected at least one lobe ∼ 75% sample. For all measured flux can be attributed to inverse Compton scattering cosmic microwave background radiation, magnetic field strengths between 0.3Beq 1.3Beq, where value Beq corresponds equipartition electrons field, assuming filling...
Context.The largest uncertainty for cosmological studies using clusters of galaxies is introduced by our limited knowledge the statistics galaxy cluster structure, and scaling relations between observables mass.
Context.A study of the structural and scaling properties temperature distribution hot, X-ray emitting intra-cluster medium galaxy clusters, its dependence on dynamical state, can give insights into physical processes governing formation evolution structure.
We present a study of the structural and scaling properties gas distributions in intracluster medium (ICM) 31 nearby () clusters observed with XMM-Newton, which together comprise Representative XMM-Newton Cluster Structure Survey (REXCESS). In contrast to previous studies, this sample is unbiased respect X-ray surface brightness cluster dynamical state, it fully samples luminosity function. The cover temperature range 2.0-8.5 keV possess variety morphologies. sampling strategy allows us...
We combine Chandra and XMM-Newton X-ray data from our previous papers with new observations Spitzer mid-infrared in order to study the nature of nuclei radio galaxies radio-loud quasars z<1.0 3CRR sample. The significant increase sample size over work, reduction bias as a result observations, availability more allow us show conclusively that almost all objects classed low-excitation optical spectroscopic studies lack radiatively efficient active nucleus. distribution absorbing columns...
We present a Chandra and XMM–Newton spectral analysis of the nuclei radio galaxies radio-loud quasars from 3CRR sample in redshift range 0.1 < z 0.5. In luminosity sampled by these objects, mostly Fanaroff–Riley type IIs (FR IIs), it has been clear for some time that population [low-excitation (LERGs)] cannot easily participate models unify narrow-line broad-line objects. show low-excitation have systematically different nuclear X-ray properties: while universally heavily absorbed component,...
We present deep LOFAR observations between 120-181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one brightest radio relic sources known. Our exploit new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part spectrum. The observations, when combined with VLA, GMRT, Chandra X-ray data, provide information about nature merger shocks their role re-accelerating relativistic particles. derive spectral index $\alpha =...
This paper presents a study of the local radio source population, by cross-comparing data from first release (DR1) LOFAR Two-Metre Sky Survey (LoTSS) with Sloan Digital (SDSS) DR7 main galaxy spectroscopic sample. The LoTSS DR1 provides deep (median rms noise 71 $\mathrm{\mu}$Jy at 150 MHz) over 424 square degrees sky, which is sufficient to detect 10615 (32 per cent) SDSS galaxies this sky area. An improved method separate active galactic nuclei (AGN) accurately sources emission powered...
ABSTRACT LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of low-frequency sky. At same time also provides excellent short baseline coverage to map diffuse extended emission. However, producing high-quality deep images challenging due presence direction-dependent calibration errors, caused by imperfect knowledge station beam shapes ionosphere. Furthermore, large data volume clock errors...
We constructed a sample of 23,344 radio-loud active galactic nuclei (RLAGN) from the catalogue derived LOFAR Two-Metre Sky Survey (LoTSS) survey HETDEX Spring field. Although separating AGN star-forming galaxies remains challenging, combination spectroscopic and photometric techniques we used gives us one largest available samples candidate RLAGN. sample, combined with recently developed analytical models, to investigate lifetime distribution show that large or giant powerful RLAGN are...
The broad-bandwidth capabilities of next generation telescopes such as the JVLA mean that spectrum any given source varies significantly within bandwidth observation. Detailed spectral analysis taking this variation into account is set to become standard practice when dealing with new broadband radio observations; it therefore vital methods are developed handle type data. In paper, we present Broadband Radio Astronomy ToolS (BRATS) software package and, use carry out detailed observations...
Ongoing and future radio surveys aim to trace the evolution of black hole growth feedback from active galactic nuclei (AGNs) throughout cosmic time; however, there remain major uncertainties in translating luminosity functions into a reliable assessment energy input as function galaxy and/or dark matter halo mass. A crucial long-standing problem is composition radio-lobe plasma that traces AGN jet activity. In this paper, we carry out systematic comparison conditions Fanaroff & Riley class I...
We carry out a systematic study of the X-ray emission from active nuclei 0.02 < z 0.7 2 Jy sample, using Chandra and XMM-Newton observations.We combine our results with those mid-infrared, optical emission-line radio observations, add them to 3CRR sources.We show that low-excitation objects in samples signs radiatively inefficient accretion.We effect jet-related on various luminosities, confirming it is main source soft for also find strong correlations between accretion-related identify...
We present the Multifrequency Snapshot Sky Survey (MSSS), first northern-sky LOFAR imaging survey. In this introductory paper, we describe in detail motivation and design of Compared to previous radio surveys, MSSS is exceptional due its intrinsic multifrequency nature providing information about spectral properties detected sources over more than two octaves (from 30 160 MHz). The broadband frequency coverage, together with fast survey speed generated by LOFAR's multibeaming capabilities,...
We present the source associations, cross-identifications, and multi-wavelength properties of faint radio population detected in deep tier LOFAR Two Metre Sky Survey (LoTSS): LoTSS Deep Fields. The first Fields data release consists imaging at 150~MHz ELAIS-N1, Lockman Hole, Bo\"{o}tes fields, down to RMS sensitives around 20, 22, 32$~\mu$Jy\,beam$^{-1}$, respectively. These fields are some best studied extra-galactic northern sky, with existing deep, wide-area panchromatic photometry from...