A5014074485- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Particle Accelerators and Free-Electron Lasers
- Dark Matter and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- Scientific Research and Discoveries
- Particle Detector Development and Performance
- Adaptive optics and wavefront sensing
- Ionosphere and magnetosphere dynamics
- Calibration and Measurement Techniques
- History and Developments in Astronomy
- Superconducting and THz Device Technology
- Magnetic confinement fusion research
- Radio Wave Propagation Studies
- Advanced X-ray Imaging Techniques
Istituto di Radioastronomia di Bologna
2015-2024
University of Calabria
2024
BOKU University
2024
National Institute for Astrophysics
2013-2023
Brera Astronomical Observatory
2022
University of Bologna
1997-2019
Osservatorio astronomico di Bologna
1997-2016
Campbell Collaboration
2012
Dublin Institute For Advanced Studies
2009
Arcetri Astrophysical Observatory
2009
The Cherenkov Telescope Array, CTA, will be the major global observatory for very high energy gamma-ray astronomy over next decade and beyond. scientific potential of CTA is extremely broad: from understanding role relativistic cosmic particles to search dark matter. an explorer extreme universe, probing environments immediate neighbourhood black holes voids on largest scales. Covering a huge range in photon 20 GeV 300 TeV, improve all aspects performance with respect current instruments....
Radio observations prove the existence of relativistic particles and magnetic field associated with intra-cluster-medium (ICM) through presence extended synchrotron emission in form radio halos peripheral relics. This observational evidence has fundamental implications on physics ICM. Non-thermal components galaxy clusters are indeed unique probes very energetic processes operating within that drain gravitational electromagnetic energy into cosmic rays fields. These strongly affect...
The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120-168 MHz imaging survey that will eventually cover the entire Northern sky. Each of 3170 pointings be observed for 8 hrs, which, at most declinations, sufficient to produce ~5arcsec resolution images with sensitivity ~0.1mJy/beam and accomplish main scientific aims which are explore formation evolution massive black holes, galaxies, clusters galaxies large-scale structure. Due compact core long baselines LOFAR, provide excellent both highly...
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$00$'$00$''$) were mapped using a fully automated direction-dependent calibration imaging...
The radio spectral index map of the Coma halo shows a progressive steepening with increasing radius. Such cannot be simply justified by models involving continuous injection fresh particles in or diffusion electrons from central regions. We propose two-phase model which relativistic injected cluster some processes (starbursts, AGNs, shocks, turbulence) during first phase past are systematically reaccelerated second for relatively long time (∼1Gyr) up to present time. show that reacceleration...
We attempt to explain the non-thermal emission arising from galaxy clusters as a result of re-acceleration electrons by compressible turbulence induced cluster mergers. In our model intracluster medium (ICM) is represented high beta plasma in which turbulent motions are driven at large scales. The corresponding injection velocities higher than Alfven velocity. As result, approximately isotropic up scale velocity gets comparable with Under hypothesis that ICM highly super- Alfvenic magnetic...
In this data release from the LOFAR Two-metre Sky Survey (LoTSS) we present 120-168MHz images covering 27% of northern sky. Our coverage is split into two regions centred at approximately 12h45m +44$^\circ$30' and 1h00m +28$^\circ$00' spanning 4178 1457 square degrees respectively. The were derived 3,451hrs (7.6PB) High Band Antenna which corrected for direction-independent instrumental properties as well direction-dependent ionospheric distortions during extensive, but fully automated,...
We present the first wide area (19 deg$^2$), deep ($\approx120-150$ {\mu}Jy beam$^{-1}$), high resolution ($5.6 \times 7.4$ arcsec) LOFAR High Band Antenna image of Bo\"otes field made at 130-169 MHz. This is least an order magnitude deeper and 3-5 times higher in angular than previously achieved for this low frequencies. The observations data reduction, which includes full direction-dependent calibration, are described here. a radio source catalogue containing 6276 sources detected over...
The Low Frequency Array (LOFAR) is an ideal instrument to conduct deep extragalactic surveys. It has a large field of view and sensitive large-scale compact emission. is, however, very challenging synthesize thermal noise limited maps at full resolution, mainly because the complexity low-frequency sky direction dependent effects (phased array beams ionosphere). In this first paper series, we present new calibration imaging pipeline that aims producing high fidelity, dynamic range images with...
Smoothed particle hydrodynamics (SPH) employs an artificial viscosity to properly capture hydrodynamical shock waves. In its original formulation, the resulting numerical is large enough suppress structure in velocity field on scales well above nominal resolution limit, and damp generation of turbulence by fluid instabilities. This could artificially random gas motions intracluster medium (ICM), which are driven infalling structures during hierarchical formation process. We show that this...
Chandra observations of the merging galaxy cluster A520 reveal a prominent bow shock with M = 2.1. This is only second clear example substantially supersonic merger front in clusters. Comparison X-ray image that previously known radio halo reveals coincidence leading edge shock, offering an interesting experimental setup for determining role shocks generation. The apparently consists two spatially distinct parts, main turbulence-driven component and cap-like forward structure related to...
The frequently observed association between giant radio halos (RHs) and merging galaxy clusters has driven present theoretical models of non-thermal emission from clusters, which are based on the idea that energy dissipated during cluster–cluster mergers could power formation RHs. To quantitatively test merger–halo connection, we first statistical study deep data X-ray observations a complete X-ray-selected sample with luminosity ⩾5 × 1044 erg s−1 redshift 0.2 ⩽ z 0.32. Using several methods...
The most important evidences for non-thermal phenomena in galaxy clusters comes from the spectacular synchrotron radio emission diffused over Mpc scale observed a growing number of massive clusters. A promising possibility to explain giant halos is given by presence relativistic electrons reaccelerated some kind turbulence generated cluster volume during merger events. With aim investigate connection between thermal and properties ICM, this paper we develope statistical magneto-turbulent...
Aims. We present the first results of an ongoing project devoted to search giant radio halos in galaxy clusters located redshift range z=0.2--0.4. One main goals our study is measure fraction massive this interval hosting a halo, and constrain expectations particle re--acceleration model for origin non--thermal emission clusters. Methods. selected 27 REFLEX here we Giant Metrewave Radio Telescope (GMRT) observations at 610 MHz 11 them. The sensitivity (1$σ$) images 35--100~$μ$Jy beam$^{-1}$...
Aims. We present the results of GMRT cluster radio halo survey. The main purposes our observational project are to measure what fraction massive galaxy clusters in redshift range –0.4 host a halo, and constrain expectations particle re-acceleration model for origin non-thermal emission.
The most important evidence of non-thermal phenomena in galaxy clusters comes from Giant Radio Halos (GRHs), synchrotron radio sources extended over Mpc scales, detected a growing number massive clusters. A promising possibility to explain these is given by "in situ" stochastic reacceleration relativistic electrons turbulence generated the cluster volume during merger events. Cassano & Brunetti (2005) have recently shown that expected fraction with GRHs and increase such mass can be...
A number of relaxed, cool-core galaxy clusters exhibit diffuse, steep-spectrum radio sources in their central regions, known as mini-halos. It has been proposed that the relativistic electrons responsible for emission have reaccelerated by turbulence generated sloshing cool core gas. We present a high-resolution MHD simulation gas cluster coupled with subgrid simulations electron acceleration to test this hypothesis. Our shows motions generate on order $\delta{v} \sim$ 50-200 km s$^{-1}$...
We analyze the properties of Large Scale Shocks in a cosmological volume size 103Mpc/h simulated with public 1.0.1 release ENZO code. Different methods to identify and characterize shocks post processing are discussed together their uncertainties. Re-ionization affects simulations, we propose fitting procedure model accurately effect re-ionization non--radiative post--processing procedure. investigate by means which uses jumps velocity variables across cells simulations this allows us have...
We have implemented an Adaptive Mesh Refinement criterion explicitly designed to increase spatial resolution around discontinuities in the velocity field ENZO cosmological simulations. With this technique, shocks and turbulent eddies developed during hierarchical assembly of galaxy clusters are followed with unprecedented resolution, even at large distances from center. By measuring spectral properties gas field, its time evolution for a reference cluster, we investigate connection between...
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 =...
We study the properties of chaotic motions in intra cluster medium using a set 20 galaxy clusters simulated with large dynamical range, Adaptive Mesh Refinement code ENZO (e.g. Norman et al.2007). The adopted setup allows us to spectral and spatial turbulent unprecedented detail, achieving an maximum available Reynolds number order R=500-1000 for largest eddies. correlations between energy these Intra Cluster Medium state host systems are studied, statistical their evolution time support...