A5050735946- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Radio Astronomy Observations and Technology
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Computational Fluid Dynamics and Aerodynamics
- Dark Matter and Cosmic Phenomena
- Ionosphere and magnetosphere dynamics
- Fluid Dynamics and Turbulent Flows
- Gas Dynamics and Kinetic Theory
- Pulsars and Gravitational Waves Research
- Particle Detector Development and Performance
- Plasma and Flow Control in Aerodynamics
- Spectroscopy and Laser Applications
- Molecular Spectroscopy and Structure
- Cosmology and Gravitation Theories
- Aerodynamics and Acoustics in Jet Flows
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Magnetic confinement fusion research
University of Hertfordshire
2017-2024
University of Tasmania
2016-2021
Stuttgart Observatory
2009-2021
Inter 3
2021
Francke Foundations
2021
Max Planck Institute for Extraterrestrial Physics
2011-2020
University of Stuttgart
2017-2019
Technical University of Munich
2012-2018
Ludwig-Maximilians-Universität München
2009-2018
Excellence Cluster Universe
2012-2018
We present a model for the concurrent formation of globular clusters (GCs) and supermassive stars (SMSs, $>10^3\,{\rm M}_\odot$) to address origin HeCNONaMgAl abundance anomalies in GCs. GCs form converging gas flows accumulate low-angular momentum gas, which accretes onto protostars. This leads an adiabatic contraction cluster increase stellar collision rate. A SMS can via runaway collisions if reaches sufficiently high density before two-body relaxation halts contraction. condition is met...
<h3>Background</h3> Cervical artery dissection (CAD) is an important cause of ischemic stroke in younger patients. However, its insufficiently understood. <h3>Objective</h3> To test the hypothesis that CAD frequently associated with recent infection. <h3>Subjects and Methods</h3> We compared prevalence infection during preceding week 43 consecutive patients acute 58 than 50 years cerebral ischemia from other causes (control patients). In subgroups patients, we correlated infectious status...
Feedback from active galactic nuclei (AGN) has become a major component in simulations of galaxy evolution, particular for massive galaxies. AGN jets have been shown to provide large amount energy and are capable quenching cooling flows. Their impact on the host galaxy, however, is still not understood. Subgrid models activity evolution context so far mostly focused star formation. To shed more light actual physics 'radio mode' part activity, we performed interaction powerful jet with...
We have carried out two-dimensional, axisymmetric, hydrodynamic numerical modelling of the evolution radio galaxy lobes. The emphasis our work is on including realistic hot-gas environments in simulations and establishing what properties resulting lobes are independent choice environmental other features models such as initial jet Mach number. simulated power we use chosen so that expect inner parts to come into pressure balance with external medium large scales; show this leads expected...
The annihilation of positrons in the Galaxy's interstellar medium produces characteristic gamma-rays with a line at 511 keV. This emission has been observed spectrometer SPI on INTEGRAL, confirming puzzling morphology bright from an extended bulge-like region, and faint disk emission. Most plausible sources are believed to be distributed throughout Galaxy. We aim constrain spectral shapes for different spatial components bulge high-resolution gamma-ray SPI, based new instrumental background...
Context. The self-enrichment scenario for globular clusters (GC) requires large amounts of residual gas after the initial formation first stellar generation. Recently, we found that supernovae may not be able to expel gas, as required explain their present-day gas-free state, and suggested a sudden accretion onto dark remnants at stage when type II have ceased plausibly lead fast expulsion.
Type-Ia supernovae result from binary systems that include a carbon-oxygen white dwarf, and these thermonuclear explosions typically produce 0.5 M_solar of radioactive 56Ni. The 56Ni is commonly believed to be buried deeply in the expanding supernova cloud. Surprisingly, SN2014J we detected lines at 158 812 keV decay (τ~8.8 days) earlier than expected several-week time scale, only ~20 days after explosion, with flux levels corresponding roughly 10% total amount Some mechanism must break...
We describe three-dimensional magnetohydrodynamical modelling of powerful radio galaxies in realistic poor cluster environments. This extends our earlier work on the hydrodynamics as a function their environment to consider magnetic field configuration lobes and its observational consequences, using model for intracluster medium, very high density contrast numerical resolution. confirm, now with model, that have characteristic trajectories power/linear size diagram which depend strongly...
Star clusters are fundamental units of stellar feedback and unique tracers their host galactic properties. In this review, we will first focus on constituents, i.e.\ detailed insight into populations surrounding ionised, warm, neutral, molecular gas. We, then, move beyond the Local Group to review star cluster at various evolutionary stages, in diverse environmental conditions accessible local Universe. At high redshift, where for formation evolution more extreme, only able observe...
Context. The existence of magnetic fields in the circumgalactic medium (CGM) is largely unconstrained. Their detection important as can have a significant impact on evolution CGM, and, turn, serve tracers for dynamical processes CGM. Aims. Using Faraday rotation polarised background sources, we aim to detect possible excess measure surrounding area nearby galaxies. Methods. We used 2461 residual measures (RRMs) observed with LOw Frequency ARray (LOFAR), where foreground contribution from...
Stellar winds and supernova (SN) explosions of massive stars (‘stellar feedback’) create bubbles in the interstellar medium (ISM) insert newly produced heavy elements kinetic energy into their surroundings, possibly driving turbulence. Most this is thermalized immediately removed from ISM by radiative cooling. The rest available for dynamics. In work we estimate amount feedback retained as when bubble walls have decelerated to sound speed ambient medium. We show that most star outweighs less...
Massive stars form in groups and their winds supernova explosions create superbubbles up to kpc size. Their ejecta are important for the dynamics of interstellar medium chemical evolution models. However, kinematics characteristic scales space time rather unexplored beyond ~10 ka. Through measurement radioactive 26Al with its decay constant ~10^6 years, we aim trace massive-star over million-year scales. Our goal is identify mixing scale spatio-kinematics such from pc scale. We use SPI...
After 25 years of quiescence, the microquasar V404 Cyg entered a new period activity in June 2015. This X-ray source is known to undergo extremely bright and variable outbursts seen at all wavelengths. It therefore an object prime interest understand accretion-ejection connections. These can, however, only be probed through simultaneous observations several We made use INTEGRAL instruments obtain long, almost uninterrupted from 2015 20$^{\mathrm{th}}$, 15:50 UTC 25$^{\mathrm{th}}$, 4:05 UTC,...
Gas expulsion is a central concept in some of the models for multiple populations and light-element anticorrelations globular clusters. If star formation efficiency was around 30 per cent gas happened on crossing timescale, this process could expel preferentially stars born with chemical composition proto-cluster gas, while special centre would remain bound. Recently, sample extragalactic, gas-free, young massive clusters has been identified that potential to test conditions expulsion. We...
We present results from two suites of simulations powerful radio galaxies in poor cluster environments, with a focus on the formation and evolution lobes. One suite models uses relativistic hydrodynamics other magnetohydrodynamics; both are set up to cover range jet powers velocities. The dynamics lobes shown be good agreement analytical previous numerical models, confirming regime that observed widths may explained if they driven by very light jets. ratio energy stored put into intracluster...
We exploited observational constraints on stars, gas and nucleosynthesis ashes for the closest region of recent massive-star formation, Scorpius-Centaurus OB2, combined them with 3D hydrodynamical simulations, in order to address physics history case superbubble. used published cold observations through PLANCK survey data processing, HERSCHEL APEX, continuum molecular line observations. analysed Galactic All Sky Survey (GASS) investigate shell structures atomic hydrogen, HIPPARCOS Gaia...
ABSTRACT Feedback from radio jets associated with active galactic nuclei (AGNs) plays a profound role in the evolution of galaxies. Kinetic power these appears to show temporal variation, but mechanism(s) responsible for this process are not yet clear. Recently, LOw Frequency ARray (LOFAR) has uncovered large populations active, remnant, and restarted jet populations. By focusing on LOFAR data Lockman Hole, work we use Radio AGNs Semi-Analytic Environments (RAiSE) dynamical model present...
The cosmic evolution of the chemical elements from Big Bang to present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle matter recurrently re-processes metal-enriched ejecta into next generation stars. study nucleosynthesis this requires understanding physics reactions, conditions at which are activated explosions, ejection mechanisms through winds transport towards cycle, hot plasma cold, star-forming gas. Due long timescales evolution, because...
Abstract We summarize the second radio synchrotron background workshop, which took place on 2022 June 15–17 in Barolo, Italy. This meeting was convened because available measurements of diffuse zero level continue to suggest that it is several times higher than can be attributed known Galactic and extragalactic sources processes, rendering least well-understood electromagnetic at present a major outstanding question astrophysics. The workshop agreed next priorities for investigations this...
Abstract Odd Radio Circles (ORCs) are a class of low surface brightness, circular objects approximately one arcminute in diameter. ORCs were recently discovered the Australian Square Kilometre Array Pathfinder (ASKAP) data and subsequently confirmed with follow-up observations on other instruments, yet their origins remain uncertain. In this paper, we suggest that could be remnant lobes powerful radio galaxies, re-energised by passage shock. Using relativistic hydrodynamic simulations...
Hydrodynamic jets, underdense with respect to their environment by a factor of up 104, were computed in axisymmetry as well 3D. They finally reached size 220 jet radii, corresponding 100 kpc sized radio galaxy. The simulations are "bipolar", involving both jets. These injected into King type density profile small stochastic variations. back-reaction the cocoons on beams center produces armlength asymmetries few percent, longer jets side higher average density. Two distinguishable bow shock...
We study the evolution of isolated and merging interstellar bubbles three stars (25, 32 60 M\odot) in a homogeneous background medium with density 10 mp /ccm via 3D-hydrodynamic simulations standard ISM thermodynamics (optically thin radiative cooling photo-electric heating) time dependent energy mass input according to stellar evolutionary tracks. vary position relative each other compare response for cases isolated, initially cospatial bubbles. Due mainly Vishniac instability, our...