A5019568218- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Fluid Dynamics Simulations and Interactions
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Computational Physics and Python Applications
- Meteorological Phenomena and Simulations
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Geophysics and Gravity Measurements
- Fullerene Chemistry and Applications
- Parallel Computing and Optimization Techniques
- Pulsars and Gravitational Waves Research
- Distributed and Parallel Computing Systems
- Particle Accelerators and Free-Electron Lasers
- Statistical Methods and Bayesian Inference
- Scientific Computing and Data Management
- Magnetic confinement fusion research
- Computational Fluid Dynamics and Aerodynamics
- Advanced Thermodynamics and Statistical Mechanics
- Advanced Data Storage Technologies
Hewlett-Packard (Germany)
2023
Leiden University
2015-2019
Istituto di Radioastronomia di Bologna
2013-2019
University of Minnesota
2016-2019
Leiden Observatory
2019
National Institute for Astrophysics
2014-2015
Max Planck Institute for Astrophysics
2008-2013
Max Planck Society
2008-2011
We present an implementation of smoothed particle hydrodynamics (SPH) with improved accuracy for simulations galaxies and the large-scale structure. In particular, we combine, implement, modify test a vast majority SPH improvement techniques in latest instalment GADGET code. use Wendland kernel functions, wake-up time-step limiting mechanism time-dependent scheme artificial viscosity, which includes high-order gradient computation shear flow limiter. Additionally, include novel prescription...
We present the first high resolution MHD simulation of cosmic-ray electron reacceleration by turbulence in cluster mergers. use an idealised model for mergers, combined with a numerical injection, cooling and electrons, to investigate evolution scale radio emission these objects. In line theoretical expectations, we time, show that CRe has potential reproduce key observables halos. particular, clusters evolve being loud or quiet, depending on their evolutionary stage during merger. thus...
We performed cosmological, magnetohydrodynamical simulations to follow the evolution of magnetic fields in galaxy clusters, exploring possibility that origin seed is galactic outflows during starburst phase evolution. To do this, we coupled a semi-analytical model for magnetized winds as suggested by Bertone, Vogt & Enßlin our cosmological simulation. find strength and structure observed clusters are well reproduced wide range parameters magnetized, only weakly depend on exact within assumed...
Previous studies have shown that CIZA J2242.8+5301 (the 'Sausage' cluster, $z=0.192$) is a massive merging galaxy cluster hosts radio halo and multiple relics. In this paper we present deep, high fidelity, low-frequency images made with the LOw-Frequency Array (LOFAR) between 115.5 179 MHz. These images, noise of 140 mJy/beam resolution $\theta_{\text{beam}}=7.3"\times5.3"$, are an order magnitude more sensitive five times higher than previous cluster. We combined LOFAR data existing GMRT...
Radio relics are patches of diffuse synchrotron radio emission that trace shock waves. Relics thought to form when intra-cluster medium electrons accelerated by cluster merger induced waves through the diffusive acceleration mechanism. In this paper, we present observations spanning 150 MHz 30 GHz `Sausage' and `Toothbrush' from Giant Metrewave Westerbork telescopes, Karl G. Jansky Very Large Array, Effelsberg telescope, Arcminute Microkelvin Imager Combined Array for Research in...
We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales galaxy clusters beyond. Structure formation drives compression turbulence, which amplify tiny seed fields to microGauss values that are observed intracluster medium. This process is intimately connected properties turbulence microphysics intra-cluster Additional roles played by merger induced shocks sweep through medium motions sloshing cool cores....
We use the results from a constrained, cosmological MHD simulation of Local Universe to predict radio halo and gamma-ray flux Coma cluster compare it current observations. The simulated magnetic field within is result turbulent amplification during build-up cluster. seed originates star-burst driven, galactic outflows. synchrotron emission calculated assuming hadronic model. follow four approaches with different distributions for cosmic-ray proton (CRp) population galaxy clusters. radial...
Particle acceleration by turbulence plays a role in many astrophysical environments. The non-linear evolution of the underlying cosmic ray spectrum is complex and can be described Fokker–Planck equation, which general has to solved numerically. We present here an implementation compute coupled considering isotropic particle pitch-angle distributions taking into account relevant energy gains losses. Our code used runtime post-processing very large fluid simulations. also propose novel method...
Giant radio relics are the arc-shaped diffuse emission regions observed in outskirts of some merging galaxy clusters. They believed to trace shock-waves intra-cluster medium. Recent observations demonstrated that prominent exhibit a steepening above 2 GHz their spectrum. This challenges standard theoretical models because shock acceleration is expected accelerate electrons very high energies with power-law distribution momentum. In this work we attempt reconcile these data shock-acceleration...
We use results from a constrained, cosmological MHD simulation of the Local Universe to predict radio halos and their evolution for volume limited set galaxy clusters compare current observations. The simulated magnetic field inside is result turbulent amplification within them, with seed originating star-burst driven, galactic outflows. evaluate three models, where we choose different normalizations Cosmic Ray proton population clusters. Similar our previous analysis Coma cluster (Donnert...
We present high resolution simulations of a multiple merger three disk galaxies including the evolution magnetic fields performed with N-body/SPH code Gadget. For first time, we embed in magnetized, low-density medium, thus modeling an ambient IGM. The include radiative cooling and model for star formation supernova feedback. progenitor disks have initial seed range 10e-9 to 10e-6 G IGM has 10e-12 G. are compared run excluding fields. show that propagation interaction-driven shocks depends...
Simulations of isolated binary mergers galaxy clusters are a useful tool to study the evolution these objects. For exceptionally massive systems they even represent only viable way simulation, because rare in typical cosmological simulations. We present new practical model for simulations based on Hernquist dark matter profile. The hydrostatic equation is solved beta-model with $\beta$ = 2/3 this potential and approximate expressions X-ray brightness Compton-y parameter derived. show detail...
We present a new code for astrophysical magneto-hydrodynamics specifically designed and optimized high performance scaling on modern future supercomputers. describe novel hybrid OpenMP/MPI programming model that emerged from collaboration between Cray, Inc. the University of Minnesota. This design utilizes MPI-RMA thread scaling, which allows to run extremely efficiently at very counts ideal latest generation multi-core many-core architectures. Such characteristics are needed in era...
The spectrum of the radio halo in Coma cluster is measured over almost two decades frequency. current data show a steepening at higher frequencies, which has implications for models origin. There an on-going debate on possibility that observed not intrinsic to emitted radiation, but instead caused by SZ effect. Recently, Planck satellite signal and its spatial distribution allowing test this hypothesis. Using results, we calculated modification effect three different ways. With first methods...
The giant radio relic in CIZA J2242.8+5301 is likely evidence of a Mpc sized shock massive merging galaxy cluster. However, the exact properties are still not clearly determined. In particular, Mach number derived from integrated spectrum exceeds X-ray temperature jump by factor two. We present here numerical study, aiming for model that consistent with majority observations this first show northern upstream and data each other. then derive progenitor masses system using standard density...
Using cosmological MHD simulations of the magnetic field in galaxy clusters and filaments we evaluate possibility to infer strength by measuring cross-correlation functions between Faraday Rotation Measures (RM) density field. We also test reliability recent estimates considering problem data quality Galactic foreground (GF) removal current datasets. Besides two self-consistent fields based on primordial seed galactic outflows analyzed here, explore a larger range models scaling up resulting...
We present an on-the-fly geometrical approach for shock detection and Mach number calculation in simulations employing smoothed particle hydrodynamics (SPH). utilize pressure gradients to select candidates define up- downstream positions. obtain hydrodynamical states the regimes with a series of normal inverted kernel weightings parallel perpendicular normals. Our detector incorporates well within SPH formalism has low computational cost. implement our into simulation code gadget alongside...
Galaxy clusters are unique laboratories to investigate turbulent fluid motions and large scale magnetic fields.Synchrotron radio halos at the center of merging galaxy provide most spectacular direct evidence presence relativistic particles fields associated with intracluster medium.The study polarized emission from is extremely important constrain properties physics acceleration transport particles.However, detecting this signal a very hard task current facilities.We use cosmological...
The archetype FR-II galaxy Cygnus A lies in a moderately rich cluster about to undergo major merger. We study the pre-merger environment using smoothed particle hydrodynamics simulations constrained by 2Ms of Chandra observations hot intracluster medium. constrain total gravitating mass and concentration parameter, provide quiescent merger-enhanced temperature profiles pre- post merger excluding central active galactic nucleus. present first detailed model sub north west A, named CygNW. find...
We present an implementation of smoothed particle hydrodynamics (SPH) with improved accuracy for simulations galaxies and the large-scale structure. In particular, we combine, implement, modify test a vast majority SPH improvement techniques in latest instalment GADGET code. use Wendland kernel functions, wake-up time-step limiting mechanism time-dependent scheme artificial viscosity, which includes high-order gradient computation shear flow limiter. Additionally, include novel prescription...
We present a novel and fast application to generate glass-like initial conditions for Lagrangian hydrodynamic schemes (e.g. Smoothed Particle Hydrodynamics (SPH)) following arbitrary density models based on weighted Voronoi tessellations combine it with improved configurations an additional particle reshuffling scheme. show our application's ability sample different kinds of features converge properly towards the given model as well configuration. analyse convergence iterations varying...
Galaxy clusters are unique laboratories to investigate turbulent fluid motions and large scale magnetic fields. Synchrotron radio halos at the center of merging galaxy provide most spectacular direct evidence presence relativistic particles fields associated with intracluster medium. The study polarized emission from is extremely important constrain properties physics acceleration transport particles. However, detecting this signal a very hard task current facilities.We use cosmological...
In galaxy clusters, modern radio interferometers observe non-thermal sources with unprecedented spatial and spectral resolution. For the first time, new data allows to infer structure of intra-cluster magnetic fields on small scales via Faraday tomography. This leap forward demands numerical models for amplification in cosmic formation—the cosmological dynamo. Here we present a novel approach astrophyiscal MHD simulations aimed resolve this small-scale dynamo future simulations. As step,...
Abstract We review models for giant radio halos in clusters of galaxies, with a focus on numerical and theoretical work. After summarising the most important observations these objects, we present an introduction to aspects hadronic models. compare using simulations find severe problems give short reacceleration show results from first simulation CRe cluster mergers. that in‐line previous work, are able elegantly explain main observables halos. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)