A5024712567- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Molecular Spectroscopy and Structure
- Solar and Space Plasma Dynamics
- Fluid Dynamics Simulations and Interactions
- Astronomy and Astrophysical Research
- Atmospheric Ozone and Climate
- Quantum optics and atomic interactions
- Atomic and Subatomic Physics Research
- Plant Water Relations and Carbon Dynamics
- Atomic and Molecular Physics
- Aeolian processes and effects
- Cosmology and Gravitation Theories
- Spectroscopy and Laser Applications
- Spacecraft and Cryogenic Technologies
- Embedded Systems and FPGA Design
- Relativity and Gravitational Theory
- Particle accelerators and beam dynamics
- Space Satellite Systems and Control
- Lattice Boltzmann Simulation Studies
- Astrophysics and Cosmic Phenomena
- Inorganic Fluorides and Related Compounds
University of St Andrews
2020-2024
Scottish Universities Physics Alliance
2020-2024
University of Exeter
2016-2022
St. Andrews University
2022
Monash University
2014-2018
Saint Mary's University
2013-2016
St. Mary's University
2013
Western University
2008-2009
Max Planck Institute of Quantum Optics
1993
We present Phantom, a fast, parallel, modular and low-memory smoothed particle hydrodynamics magnetohydrodynamics code developed over the last decade for astrophysical applications in three dimensions. The has been with focus on stellar, galactic, planetary high energy astrophysics already used widely studies of accretion discs turbulence, from birth planets to how black holes accrete. Here we describe test core algorithms as well modules magnetohydrodynamics, self-gravity, sink particles,...
We investigate whether or not the low ionisation fractions in molecular cloud cores can solve `magnetic braking catastrophe', where magnetic fields prevent formation of circumstellar discs around young stars. perform three-dimensional smoothed particle non-ideal magnetohydrodynamics (MHD) simulations gravitational collapse one solar mass cores, incorporating effects ambipolar diffusion, Ohmic resistivity and Hall effect alongside a self-consistent calculation chemistry assuming 0.1 micron...
We present hydrodynamic simulations of the common envelope binary interaction between a giant star and compact companion carried out with adaptive mesh refinement code enzo smooth particle hydrodynamics phantom. These mimic parameters one by Passy et al. but assess impact larger, more realistic initial orbital separation on simulation outcome. conclude that for both codes post-common is somewhat larger amount unbound mass slightly greater when wide enough does not yet overflow or just...
view Abstract Citations (180) References (64) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multiwavelength Observations of Short-Timescale Variability in NGC 4151. IV. Analysis Continuum Edelson, R. A. ; Alexander, T. Crenshaw, D. M. Kaspi, S. Malkan, Peterson, B. Warwick, Clavel, J. Filippenko, V. Horne, K. Korista, Kriss, G. Krolik, H. Maoz, Nandra, O'Brien, P. Penton, Yaqoob, Albrecht, Alloin, Ayres, Balonek, Barr, Barth, Bertram, Bromage, E. Carini,...
We present results from the first radiation non-ideal magnetohydrodynamics (MHD) simulations of low-mass star cluster formation that resolve fragmentation process down to opacity limit. model 50~M$_\odot$ turbulent clouds initially threaded by a uniform magnetic field with strengths 3, 5 10 and 20 times critical mass-to-magnetic flux ratio, at each strength, we both an ideal (including Ohmic resistivity, ambipolar diffusion Hall effect) MHD cloud. Turbulence fields shape large-scale...
The formation of a protostellar disc is natural outcome during the star process. As gas in molecular cloud core collapses under self-gravity, angular momentum will slow its collapse on small scales and promote disc. Although momenta dense star-forming cores remain to be fully characterized observationally, existing data indicates that typical have enough form relatively large, 100 au-scale, rotationally supported discs, as illustrated by hydrodynamic simulations. However, clouds are observed...
Modelling AGN feedback in numerical simulations is both technically and theoretically challenging, with numerous approaches having been published the literature.We present a study of five distinct to modelling within gravitohydrodynamic major mergers Milky Way-sized galaxies.To constrain differences only be between models, all start from same initial conditions use star formation algorithm.Most algorithms have key aspects: black hole accretion rate, energy rate method, particle algorithm,...
We present results from radiation non-ideal magnetohydrodynamics (MHD) calculations that follow the collapse of rotating, magnetized, molecular cloud cores to stellar densities. These are first such include all three effects: ambipolar diffusion, Ohmic resistivity, and Hall effect. employ an ionization model in which cosmic ray dominates at low temperatures thermal takes over high temperatures. explore effects varying rate ζcr = 10−10 10−16 s−1. Models with rates ≳10−12 s−1 produce...
We extend our previous discussion of the resonant nonlinear Faraday effect in terms precession an induced quadrupole moment to realistic experimental situations where depopulation, repopulation, and hyperfine optical pumping contribute. derive, lowest order light intensity, analytical expression for magnetorotation angle near electric-dipole resonance atomic medium arbitrary spins. find excellent quantitative agreement with absolute measurements performed on Cs ${\mathit{D}}_{2}$ line.
We investigate the formation and fragmentation of discs using a suite 3D smoothed particle radiative magnetohydrodynamics simulations. Our models are initialized as 1 M⊙ rotating Bonnor–Ebert spheres that threaded with uniform magnetic field. examine effect including ideal non-ideal fields, orientation strength field, initial rotational rate. follow gravitational collapse early evolution each system until final classification protostellar disc can be determined. Of our 105 models, 41...
Non-ideal magnetohydrodynamic (MHD) processes -- namely Ohmic resistivity, ambipolar diffusion and the Hall effect modify early stages of star formation process surrounding environment. Collectively, they have been shown to promote disc or hinder outflows. But which non-ideal has greatest impact? Using three-dimensional smoothed particle radiation MHD simulations, we model gravitational collapse a rotating, magnetised cloud through first hydrostatic core phase shortly after stellar core. We...
ABSTRACT We carry out three-dimensional smoothed particle hydrodynamics simulations to study the role of gravitational and drag forces on concentration large dust grains (St > 1) in spiral arms gravitationally unstable protoplanetary discs, resulting implications for planet formation. find that both gravity play an important evolution grains. If we include both, would otherwise be partially decoupled will become well coupled trace spirals. For most influenced by (with Stokes numbers...
In partially ionised plasmas, the magnetic field can become decoupled from neutral gas and diffuse through it in a process known as ambipolar diffusion. Although diffusion has been implemented several grid codes, we here provide an implementation smoothed particle magnetohydrodynamics (SPMHD). We use strong coupling approximation which ion density is negligible, allowing single fluid approach. The equations are derived to conserve energy, positive definite contribution entropy. test both...
We investigate the effect of non-ideal magnetohydrodynamics (MHD) on formation binary stars using a suite three-dimensional smoothed particle simulations gravitational collapse 1 M⊙, rotating, perturbed molecular-cloud cores. Alongside role Ohmic resistivity, ambipolar diffusion and Hall effect, we also examine effects magnetic field strength, orientation amplitude density perturbation. When modelling sub-critical cores, ideal MHD models do not whereas to form single protostars. In...
We present Ekster, a new method for simulating star clusters from birth in live galaxy simulation that combines the smoothed-particle hydrodynamics (SPH) Phantom with $N$-body PeTar. With it becomes possible to simulate individual stars only moderately high resolution gas, allowing us study whole sections of rather than be restricted clouds. use this and cluster formation spiral arms, investigating massive GMCs arm regions lower mass clouds, two models different potentials. After selecting...
We present a simple quantitative description of the lowest-order nonlinear Faraday effect an atomic vapor by modeling as Hanle-type precession quadrupole moment induced optical pumping. This gives medium symmetry uniaxial birefringence, and rotation is expressed in terms this birefringence. obtain expressions for transitions between states arbitrary angular momenta; new match results obtained earlier case depopulation The novel aspects are that only level populations intervene no explicit...
We examine the correlation between star formation rate (SFR) and black hole accretion (BHAR) across a suite of different AGN feedback models, using time evolution merger simulation. By considering three stages evolution, distinction nuclear outer regions formation, we consider 63 cases. Despite many models fitting M-\sigma\ relationship well, there are often distinct differences in SFR-BHAR correlations, with close to linear trends only being present after merger. Some also show parameter...
What cosmic ray ionisation rate is required such that a non-ideal magnetohydrodynamics (MHD) simulation of collapsing molecular cloud will follow the same evolutionary path as an ideal MHD or purely hydrodynamics simulation? To investigate this question, we perform three-dimensional smoothed particle simulations gravitational collapse rotating, one solar mass, magnetised cores, include Ohmic resistivity, ambipolar diffusion, and Hall effect. We assume uniform grain size $a_\text{g} = 0.1μ$m,...
We demonstrate the formation of gravitationally unstable discs in magnetized molecular cloud cores with initial mass-to-flux ratios 5 times critical value, effectively solving magnetic braking catastrophe. model gravitational collapse through to stellar core, using Ohmic resistivity, ambipolar diffusion and Hall effect canonical cosmic ray ionization rate $ζ_\text{cr} = 10^{-17}$ s$^{-1}$. When field rotation axis are initially aligned, a $\lesssim1$~au disc forms after first core phase,...
Are the kG-strength magnetic fields observed in young stars a fossil field left over from their formation or are they generated by dynamo? We use radiation non-ideal magnetohydrodynamics simulations of gravitational collapse rotating, magnetized molecular cloud core 17 orders magnitude density, past first hydrostatic to second, stellar core, examine hypothesis. Whereas previous work, we found that excess 10 kG can be implanted at birth, this assumed ideal (MHD), i.e. gas is coupled field....
Non-ideal magnetohydrodynamics (MHD) is the dominant process. We investigate effect of magnetic fields (ideal and non-ideal) turbulence (sub- transsonic) on formation circumstellar discs that form nearly simultaneously with protostar. This done by modelling gravitational collapse a 1~M$_\odot$ gas cloud threaded field imposed both rotational turbulent velocities. are parallel/anti-parallel perpendicular to rotation axis, two rates four Mach numbers. Disc occurs preferentially in models...
We test the hypothesis that initial mass function (IMF) is determined by density probability distribution (PDF) produced supersonic turbulence. compare 14 simulations of star cluster formation in 50 solar molecular cloud cores where turbulence contains either purely solenoidal or compressive modes, each case resolving fragmentation to opacity limit determine resultant IMF. find statistically indistinguishable IMFs between two sets calculations, despite a factor difference rate and standard...
ABSTRACT We perform adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) cosmological zoom simulations of a region around forming galaxy cluster, comparing the ability methods to handle successively more complex baryonic physics. In simplest, non-radiative case, two are in good agreement with each other, but SPH generate central cores slightly lower entropies virial shocks at larger radii, consistent what has been seen previous studies. The inclusion radiative cooling,...