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S. T. Maddison

Publications and source records attributed to S. T. Maddison.

23 records · Page 2Linked to original sources

Gap Formation in the Dust Layer of 3D Protoplanetary Disks

We numerically model the evolution of dust in a protoplanetary disk using a two-phase (gas+dust) Smoothed Particle Hydrodynamics (SPH) code, which is non-self-gravitating and locally isothermal. The code follows the three dimensional distribution of dust in a protoplanetary disk as it interacts with the gas via aerodynamic drag. In this work, we present the evolution of a disk comprising 1% dust by mass in the presence of an embedded planet for two different disk configurations: a small, minimum mass solar nebular (MMSN) disk and a larger, more massive Classical T Tauri star (CTTS) disk. We then vary the grain size and planetary mass to see how they effect the resulting disk structure. We find that gap formation is much more rapid and striking in the dust layer than in the gaseous disk and that a system with a given stellar, disk and planetary mass will have a different appearance depending on the grain size and that such differences will be detectable in the millimetre domain with ALMA. For low mass planets in our MMSN models, a gap can open in the dust disk while not in the gas disk. We also note that dust accumulates at the external edge of the planetary gap and speculate that the presence of a planet in the disk may facilitate the growth of planetesimals in this high density region.

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Science Programs for a 2 m-class Telescope at Dome C, Antarctica: PILOT, the Pathfinder for an International Large Optical Telescope

The cold, dry and stable air above the summits of the Antarctic plateau provides the best ground-based observing conditions from optical to sub-mm wavelengths to be found on the Earth. PILOT is a proposed 2 m telescope, to be built at Dome C in Antarctica, able to exploit these conditions for conducting astronomy at optical and infrared wavelengths. While PILOT is intended as a pathfinder towards the construction of future grand-design facilities, it will also be able to undertake a range of fundamental science investigations in its own right. This paper provides the performance specifications for PILOT, including its instrumentation. It then describes the kinds of science projects that it could best conduct. These range from planetary science to the search for other solar systems, from star formation within the Galaxy to the star formation history of the Universe, and from gravitational lensing caused by exo-planets to that produced by the cosmic web of dark matter. PILOT would be particularly powerful for wide-field imaging at infrared wavelengths, achieving near-diffraction limited performance with simple tip-tilt wavefront correction. PILOT would also be capable of near-diffraction limited performance in the optical wavebands, as well be able to open new wavebands for regular ground based observation; in the mid-IR from 17 to 40 microns and in the sub-mm at 200 microns.

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Numerical Modelling of Dusty Debris Disks

Infrared and submillimetre observations of nearby Vega-like stars have revealed a number of clumpy, asymmetric dust debris disks. Previous studies using semi-analytical and numerical methods have suggested planetary companions of various mass as the likely cause of most examples of disk asymmetry. In this paper, we modify an N-body symplectic gravitational integrator to include radiation terms and conduct medium-resolution parameter searches to identify likely planetary candidates in observed Vega-like systems. We also present high resolution models of Vega and epsilon Eridani, comparing our results to those of previous authors, and a new model for Fomalhaut.

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Building Planets with Dusty Gas

We have developed a new numerical technique for simulating dusty-gas flows. Our unique code incorporates gas hydrodynamics, self-gravity and dust drag to follow the dynamical evolution of a dusty-gas medium. We have incorporated several descriptions for the drag between gas and dust phases and can model flows with submillimetre, centimetre and metre size "dust". We present calculations run on the APAC* supercomputer following the evolution of the dust distribution in the pre-solar nebula. *Australian Partnership for Advanced Computing

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Galactic Cannibalism: the Origin of the Magellanic Stream

We are in a privileged location in the Universe which allows us to observe galactic interactions from close range -- the merger of our two nearest dwarf satellite galaxies, the LMC and SMC. It is important to understand the local merger process before we can have confidence in understanding mergers at high redshift. We present high resolution Nbody+SPH simulations of the disruption of the LMC and SMC and the formation of the Magellanic Stream, and discuss the implications for galaxy formation and evolution.

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