Research, Alice Quillen

Extrasolar Planet Prediction/Detection

Planets strongly influence structure in nearby circumstellar disks. Dynamical models can be used to infer the presence of an undetected planet through this interaction. This technique is complimentary to radial velocity and transit techniques as we can probe for planets in outer extrasolar systems and in young systems. Our recent work includes also constraints on planetary embryos in disks where they lack gaps or clearings and an estimate for the total number of giant planets residing in debris disks with central clearings.
Our group has proposed models for 3 planets, outer planets in the Fomalhaut, CoKuTau/4 system (now ruled out) and Epislon Eridani systems (model now obsolete). A planet with properties consistent with those predicted in the Fomalhaut system has been discovered, confirming the earlier predictions.
For a recent talk (Mar 2009 @ LLE): Pinpointing planets in circumstellar disks (PPT)
Talk April 2007 Finding extrasolar planets by how they sculpt circumstellar disks (PPT)

The prediction of a planet residing in the Fomalhaut system. In 2008, a planet was subsequently discovered in an orbit remarkably close to that predicted. Predictions for a planet just inside Fomalhaut's eccentric ring, PDF We predicted in 2006 from the dust morphology that there is a massive planet just interior to the dust ring with mass in the range between Neptune and Saturn with a semi-major axis of about 119AU, longitude of periastron and eccentricity, 0.1, the same as the eccentric dusty ring. The scenario breaks the degeneracies of the pericenter glow model by requiring the planet to account for both ring eccentricity and clearing edge slope. The predicted semi-major axis of 119AU differs by only 4AU from that, 115AU, estimated by Kalas et al. The elegant prediction of HD 74156D by Barnes and Raymond subsequently detected via the radial velocity technique was discussed by its discoverers (Bean et al. 2008). HD 74156D is the first exoplanet to have been predicted prior to discovery.
We argue that Pluto mass planetary embryos are embedded in the disks of AU Microscopii, Beta Pictoris and Fomalhaut, Planetary embryos and planetesimals residing in thin debris disks , astro-ph , PDF
Better estimates for the mass of a planet capable of truncating a collisional dusty disk such as Fomalhaut's, Diffusive low optical depth particle disks truncated by planets, PDF
On how many giant planets there are in other systems; Peter's paper! The Total Number of Giant Planets in Debris Disks with Central Clearings, astroph
How to estimate what kinds of planets can open gaps in accreting circumstellar disks: The Minimum Gap-opening Planet Mass in an Irradiated Circumstellar Accretion Disk, astro-ph , PDF
Predictions for the million year old planet and disk of CoKuTau/4, On the Planet and the Disk of CoKuTau/4, PDF While this planet is now ruled out because this system is a stellar binary (work by Kraus and Ireland), the model may be applicable to other young systems with inner clearings.
An early model for an extra-solar planet in the Epsilon Eridani system, Structure in the Epsilon Eridani Dusty Disk Caused by Mean Motion Resonances with a 0.3 Eccentricity Planet at Periastron, PDF This model is essentially obsolete as Jane Greaves and collaborators showed that some of the clumps modelled were background objects.
Outflows are predicted to order of magnitude from forming Jovian planets, Do Proto-jovian Planets Drive Outflows? When David Trilling and I wrote this paper our idea that planets might drive an outflow was novel. However some recent numerical studies have more or less confirmed our order of magnitude estimates and predict that ALMA should be able to detect Proto-Jovian outflows.

Simulating Disks on the GPU

We think we have an all pairs NBody + Keplerian dynamics 2nd order democratic heliocentric symplectic integator running on the GPU (graphics processing unit). This is a parallel code running with CUDA on a video card that puts the many processors on board to work while taking advantage of fast shared memory.
Our preliminary code can be found here: AQkepnbody code for GPU , Description of code DPS 08 poster pdf , DPS 08 poster ppt

Alex's simulations of planet migration into a fully self-gravitating planetsimal disk, code written in CUDA and on the GPU, Planet Migration through a Self-Gravitating Planetesimal Disk

Celestial Mechanics and Circumstellar Disk Morphology

Talk Jan 2007 on Resonance Capture (PPT)

General theory for predicting the likelihood of resonant capture covering the non-adiabatic limit, Reducing the Probability of Capture , PDF , Errata
Related to the proposed outer eccentric planet in the Fomalhaut system: Chaotic zone boundary for low free eccentricity particles near an eccentric planet, PDF
On the morphology of protostellar disks (with Peggy!), Driving spiral arms in the debris disks of HD 100546 and HD 141569A , PDF and The Evolution of Protoplanetary Disk Edges , PDF and Planets Rapidly Create Holes in Young Circumstellar Disks and Observational Properties of Protoplanetary Disk Gaps
More on the morphology of protostellar disks (Pasha's paper!), The formation of an eccentric gap in a gas disk by a planet in an eccentric orbit
How to send alot of stuff into a star, Production of Star-grazing and Star-impacting Planetesimals via Orbital Migration of Extrasolar Planets , PDF . And yet stars are not polluted, Using a Hipparcos-derived Hertzsprung-Russell Diagram to Limit the Metallicity Scatter of Stars in the Hyades: Are Stars Polluted? , PDF This initial study showed with photometry that stars in an open cluster have nearly identical metallicity; scatter delta[Fe/H]<0.03. This limit has been confirmed and for more clusters with spectroscopic studies.